-
Question 1
Correct
-
Which of the following does not contribute to increased stroke volume during exercise?
Your Answer: Increased length of filling time during diastole
Explanation:Prolonged aerobic exercise training may also increase stroke volume, which frequently results in a lower (resting) heart rate. Reduced heart rate prolongs ventricular diastole (filling), increasing end-diastolic volume, and ultimately allowing more blood to be ejected.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 2
Incorrect
-
The following determines the strength of contraction
Your Answer: Depolarization
Correct Answer: Plateau phase
Explanation:The plateau phase which follows is unique to myocytes and results from a small, but sustained inward calcium current through L-type calcium channels lasting 200-400 ms. This calcium influx is caused by a combined increase in permeability of the cell and especially the sarcolemmal membranes to calcium. This plateau (or refractory) phase in myocyte action potential prevents early reactivation of the myocytes and directly determines the strength of contraction
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 3
Incorrect
-
Dicrotic notch is produced by which valves?
Your Answer: Pulmonary and aortic
Correct Answer: Aortic
Explanation:The graph of aortic pressure throughout the cardiac cycle displays a small dip (the incisure or dicrotic notch) which coincides with the aortic valve closure. The dip in the graph is immediately followed by a brief rise (the dicrotic wave) then gradual decline.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 4
Correct
-
What is the isolated effect of B2 stimulation on the coronaries.
Your Answer: Vasoconstriction
Explanation:Norepinephrine and epinephrine are agonists for all adrenergic receptor subtypes, although with varying affinities. Based on their physiology and pharmacology, adrenergic receptors have been divided into two principal types: alpha and betta. These types have been further differentiated into alpha-1, alpha-2, b1, and b2 receptors. Alpha-1 Receptors are located on postsynaptic cells in smooth muscle and elicit vasoconstriction. alpha-2 Receptors are localized on presynaptic membranes of postganglionic nerve terminals that synthesize norepinephrine. When activated by catecholamines, alpha-2 receptors act as negative feedback controllers, inhibiting further norepinephrine release. Activation of myocardial b1 receptors stimulates the rate and strength of cardiac contraction, and consequently increases cardiac output. b1 Receptor activation also stimulates renin release from the kidney. Another class of antihypertensive agents acts by inhibiting b1 receptors. Activation of b2 receptors by epinephrine relaxes vascular smooth muscle and results in vasodilation.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 5
Correct
-
Which is the commonest cardiovascular abnormality seen in an adult patient with Marfan’s syndrome?
Your Answer: Aortic aneurysm
Explanation:Marfan syndrome (MFS) is a genetic disorder of connective tissue. The degree to which people are affected varies. People with Marfan’s tend to be tall, and thin, with long arms, legs, fingers and toes. They also typically have flexible joints and scoliosis. The most serious complications involve the heart and aorta with an increased risk of mitral valve prolapse and aortic aneurysm.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 6
Incorrect
-
The term cardiac output refers to the amount of blood pumped by the heart in one minute. The rate in women is around 5 L/min, whereas in men is somewhat higher, around 5.5 L/min. Which of the equations below best describes cardiac output?
Your Answer: Stroke volume / heart rate
Correct Answer: Stroke volume x heart rate
Explanation:Cardiac output (CO) is calculated by multiplying stroke volume (SV) by heart rate (HR): CO = HR x SV As a result, both stroke volume and heart rate are exactly proportional to cardiac output. There will be an increase in cardiac output if the stroke volume or heart rate increases, and a reduction in cardiac output if the stroke volume or heart rate lowers.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 7
Incorrect
-
In the cardiac cycle, all of the following are true except:
Your Answer: The ejection fraction is about 55%
Correct Answer: Mitral valve is closed by contraction of papillary muscles
Explanation:The mitral valve closes during the phase of isovolumetric contraction. After atrial systole blood is pumped into the ventricles. When the ventricles begin to contract the pressure in the ventricles increases enough to close the mitral valve but not to open the aortic and pulmonary valves. During this phase the volume remains constant but the pressure continues to increase.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 8
Incorrect
-
When observing a JVP, which of the following would lead to prominent v waves?
Your Answer: Cardiac Tamponade
Correct Answer: Tricuspid regurgitation
Explanation:The v wave corresponds to Venous filling when the tricuspid valve is closed and venous pressure increases from venous return. In Tricuspid regurgitation there is additional blood from the regurgitant flow and thus this leads to a more prominent V wave.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 9
Incorrect
-
Which factors increase the end-diastolic volume?
Your Answer: Standing
Correct Answer: Constriction of veins
Explanation:End diastolic volume is also known as preload. It is the amount of blood the heart contracts against. Constriction of veins will decrease venous pooling and increase venous return, hence increasing the end diastolic volume. Standing will increase venous pooling hence decreasing venous return and end diastolic volume. Raised intrapericardial pressure will also decrease venous return and hence end diastolic volume.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 10
Incorrect
-
Which of the following antiarrhythmic drugs may be used in the treatment of long QT syndrome?
Your Answer: Propafenone
Correct Answer: Atenolol
Explanation:Beta-blockers are the mainstay of treatment in long QT syndrome. Implantable cardioverter-defibrillators are the most effective treatment in genotypes with a high risk of recurrence.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 11
Correct
-
The following products of the vascular endothelium produce vasodilation except:
Your Answer: Endothelin
Explanation:Vascular endothelial growth factor (VEGF) is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. It is part of the system that restores the oxygen supply to tissues when blood circulation is inadequate. VEGF’s normal function is to create new blood vessels during embryonic development, new blood vessels after injury, muscle following exercise, and new vessels (collateral circulation) to bypass blocked vessels.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 12
Incorrect
-
The approximate incidence of deep venous thrombosis (DVT) in the general population each year is:
Your Answer: 0.1 per 1000
Correct Answer: 1 per 1000
Explanation:About 1 in 1000 adults per year has DVT, but as of 2011, available data is dominated by North American and European populations. DVT is rare in children, with an incidence of about 1 in 100,000 a year. From childhood to old age, incidence increases by a factor of about 1000, with almost 1% of the elderly experiencing DVTs yearly.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 13
Correct
-
Question 14
Correct
-
Concerning surface anatomy, where is the mitral valve found?
Your Answer: Situated in the 4th intercostal space left to the sternum
Explanation:The mitral valve is situated in the left 4th intercostal space just beneath the sternum.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 15
Correct
-
B1 adrenergic stimulation produces:
Your Answer: Increase in calcium cytosolic concentration
Explanation:Norepinephrine secreted by the sympathetic endings binds to B1 receptors, and the resulting increase in intracellular cAMP facilitates the opening of L channels, increasing Ica and the rapidity of the depolarization phase of the impulse and activates PKA which leads to phosphorylation of the voltage-gated Ca2+ channels, causing them to spend more time in the open state.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 16
Incorrect
-
Why does arterial blood pressure drop during pregnancy?
Your Answer: Pregnancy has a hypodynamic circulation
Correct Answer: Progesterone relaxes vascular smooth muscle
Explanation:Progesterone relaxes vascular smooth muscle thus resulting In a decrease in total peripheral resistance. This accounts for the increase in the cardiac output.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 17
Correct
-
Stimulation of the carotid sinus results in:
Your Answer: Drop in blood pressure
Explanation:Stimulation of the carotid sinus will result in an increase in the baroreceptor discharge. This will travel via the afferent nerves to the medulla. Signals will pass through the vagus nerve to decrease the sympathetic outflow to the heart and the blood vessels. This inhibition will result in vasodilation of the blood vessels, venodilation and bradycardia hence decreasing the total peripheral resistance and lowering the blood pressure.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 18
Correct
-
Question 19
Incorrect
-
Regarding the length of systole and diastole which of the following is true?
Your Answer: Cardiac muscle can be tetanise
Correct Answer: The duration of systole is more fixed than diastole
Explanation:The duration of systole is more fixed than the duration of diastole. When the heart rate increases the timing of systole remains more or less the same however, diastole decreases.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 20
Incorrect
-
Most of the venous blood returns to the heart through the:
Your Answer: Left atrium
Correct Answer: Coronary sinus and anterior cardiac veins
Explanation:Most of the venous blood returns to the heart via the coronary sinus and the anterior cardiac veins which drain into the right atrium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 21
Correct
-
What are the diagnostic criteria for an ST segment elevation type of acute myocardial infarction?
Your Answer: 1 mm ST elevation in 2 limb leads
Explanation:The current guidelines for the ECG diagnosis of the ST segment elevation type of acute myocardial infarction require at least 1 mm (0.1 mV) of ST segment elevation in the limb leads, and at least 2 mm elevation in the precordial leads. These elevations must be present in anatomically contiguous leads. (I, aVL, V5, V6 correspond to the lateral wall; V3-V4 correspond to the anterior wall ; V1-V2 correspond to the septal wall; II, III, aVF correspond to the inferior wall.)
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 22
Correct
-
Question 23
Incorrect
-
What is the normal duration of the ST segment?
Your Answer: 0.4 s
Correct Answer: 0.08 s
Explanation:The ST segment lies between the QRS complex and the T-wave. The normal duration of the ST segment is 0.08 s. ST-segment elevation or depression may indicate myocardial ischaemia or infarction.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 24
Incorrect
-
Which of the following would be a contraindication to thrombolysis?
Your Answer: Controlled hypertension
Correct Answer: Intracranial neoplasm
Explanation:Absolute contraindications to thrombolysis include:Previous intracranial bleeding at any timeStroke in less than 6 monthsClosed head or facial trauma within 3 monthsSuspected aortic dissectionIschemic stroke within 3 months (except in ischemic stroke within 3 hours time)Active bleeding diathesisUncontrolled high blood pressure (>180 systolic or >100 diastolic)Known structural cerebral vascular lesionArterio-venous malformationsThrombocytopeniaKnown coagulation disordersAneurysmBrain tumoursPericardial effusionSeptic embolus
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 25
Correct
-
Which of the following results in the resting membrane potential of a myocyte?
Your Answer: Activation of outward K+ channels
Explanation:Phase 0 is caused by the sodium current. Voltage gated sodium channels open leading to the influx of sodium into the cardiac muscle cell. Phase 1 is the rapid transient repolarization phase which is caused by the inactivation of the voltage gated sodium channels and opening of the voltage gated potassium channels along with opening of the slow calcium channels. Phase 2 which is the plateau is caused by opening of the slow calcium channels. Phase 4 is caused by closing of the slow calcium channels and opening of the potassium channels leading to efflux of potassium leading to the establishment of the resting membrane potential.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 26
Incorrect
-
Concerning surface anatomy, where is the apex beat found?
Your Answer: 5th intercostal space anterior axillary line
Correct Answer: 5th intercostal space mid clavicular line
Explanation:The location of the apex beat may vary but it is mostly found in the left 5th intercostal space 6 cm from the anterior median line or in the mid clavicular line.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 27
Incorrect
-
Question 28
Correct
-
Coronary arteries fill up during
Your Answer: Diastole
Explanation:During contraction of the ventricular myocardium (systole), the subendocardial coronary vessels (the vessels that enter the myocardium) are compressed due to the high ventricular pressures. This compression results in momentary retrograde blood flow (i.e., blood flows backward toward the aorta) which further inhibits perfusion of myocardium during systole. However, the epicardial coronary vessels (the vessels that run along the outer surface of the heart) remain open. Because of this, blood flow in the sub endocardium stops during ventricular contraction. As a result, most myocardial perfusion occurs during heart relaxation (diastole) when the subendocardial coronary vessels are open and under lower pressure.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 29
Correct
-
The AV Node:
Your Answer: It decelerates impulses passing to the ventricles
Explanation:The action potentials in the sinoatrial (SA) and atrioventricular (AV) nodes are largely due to Ca2+, with no contribution by Na+ influx. The depolarization continues to conduct slowly through the atrioventricular (AV) node. The AV node is located in the right posterior portion of the interatrial septum. This is a small, bean-shaped. The atrial conductive system is organized so that the cardiac impulse does not travel from the atria into the ventricles too rapidly; this delay allows the atria to empty before ventricular contraction begins. It is the AV node and its adjacent conductive fibers that delay this transmission into the ventricles. Conduction through the AV Node is represented on the ECG by the PR interval.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 30
Correct
-
Water hammer pulse is found in:
Your Answer: Aortic insufficiency
Explanation:Watson’s water hammer pulse is the medical sign which describes a pulse that is bounding and forceful, rapidly increasing and subsequently collapsing, as if it were the sound of a water hammer that was causing the pulse. A water hammer was a Victorian toy in which a tube was half filled with fluid, the remainder being a vacuum. The child would invert and reinvert the tube; each time the impact of the fluid at each end would sound like a hammer blow. This is associated with increased stroke volume of the left ventricle and decrease in the peripheral resistance leading to the widened pulse pressure of aortic regurgitation.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 31
Incorrect
-
Direct conduction from the atrium to the ventricles is prevented by:
Your Answer: Bundle of his
Correct Answer: Annulus fibrosus
Explanation:The annulus fibrosus disconnects the syncytium complex. The atria are rapidly activated however the activation peters out when the insulating layer-the annulus fibrosus-is reached.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 32
Incorrect
-
According to Poiseuille’s formula, which 1 of the following will lead to increased flow?
Your Answer: Less turbulent flow
Correct Answer: Shorter tube
Explanation:V = π p r4 / 8 η lwhere V = discharge volume flow (m3/s)p = pressure difference between the ends of the pipe (N/m2, Pa)r = internal radius of pipe (m)l = length of pipe (m)η = viscosity of fluid
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 33
Incorrect
-
A 27 year old man presents with a regular tachycardia of 190 bpm. He is healthy and has no past medical history. Blood pressure and bloods are all within normal parameters however the ECG confirms a narrow complex tachycardia. The tachycardia persists after giving IV adenosine 3mg and then 6mg. What should be the next step in management of this patient?
Your Answer: DC Cardioversion
Correct Answer: IV 12mg adenosine
Explanation:For narrow complex tachycardias with no compromise then vagal manoeuvres should be trialled first. The Valsalva manoeuvre should be the first vagal manoeuvre tried and works by increasing intra-thoracic pressure and affecting baroreceptors (pressure sensors) within the arch of the aorta. It is carried out by asking the patient to hold his/her breath while trying to exhale forcibly as if straining during a bowel movement. Adenosine, an ultra-short-acting AV nodal blocking agent, is indicated if vagal manoeuvres are not effective. Adenosine may be safely used during pregnancy. After giving 3mg of adenosine with no effect, 6mg should be tried. If this fails then 12mg should be trialled. If adenosine fails then Verapamil or a beta blocker can be used as alternatives. If the patient is hemodynamically unstable or other treatments have not been effective, synchronized electrical cardioversion may be used.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 34
Incorrect
-
Factors influencing cardiac output include which of the following?
Your Answer: Stroke volume
Correct Answer: All of the above
Explanation:There is a correlation between resting CO and body surface area. The output per min per square meter of body surface (the cardiac index) averages 3.2l.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 35
Incorrect
-
Which one of the following is a cause of a soft second heart sound?
Your Answer: Mitral regurgitation
Correct Answer: Aortic stenosis
Explanation:Second heart sound (S2) forms the dub of lub-dub and is composed of components A2 and P2. • loud: hypertension• soft: AS• fixed split: physiological split (normally occurs during inhalation), right bundle branch block, pulmonary stenosis, and atrial septal defect.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 36
Incorrect
-
According to Starling's law of the heart:
Your Answer: Cardiac output is increased when the sympathetic nerves are stimulated
Correct Answer: The extent of the preload is proportional to the end-diastolic volume
Explanation:Frank starlings law describes that an increase in the venous return or the end diastolic volume will cause an increase in the stroke volume/ preload and also cardiac output. It stems from the fact that increased venous return will increase the stretch on the ventricular muscle fibers. The sarcomere will stretch a considerable length that is needed for maximum contraction and the development of tension in the muscle fiber. The greater the venous return the greater the cardiac output. This relationship is directly proportional.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 37
Correct
-
Question 38
Incorrect
-
Which of the following has the shortest duration:
Your Answer: PR interval
Correct Answer: Atrial systole: 0.1s
Explanation:Atrial systole: 0.1sAtrial diastole: around 0.4sVentricular diastole: 0.4-0.53s.Ventricular systole: 0.27sPR interval: 0.12-0.2 s
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 39
Incorrect
-
All of the following are consistent with the indicator dilution method except---
Your Answer: The cardiac output is equal to the amount of indicator injected divided by its average concentration in arterial blood after a single circulation though the heart
Correct Answer: In thermodilution, the indicator used is warm saline
Explanation:In thermodilution, the indicator used is cold saline.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 40
Incorrect
-
Regarding cardiac muscle contractility, the afterload refers to:
Your Answer: The degree of myocardial stretch before contraction
Correct Answer: The resistance against which blood is expected
Explanation:The afterload for the left ventricle is the aortic pressure. Hence it is this pressure that offers resistance against which the blood is to be expelled from the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 41
Correct
-
Which factor produced by the endothelium is responsible for the regulation of vascular cell growth?
Your Answer: Vascular endothelial growth factor (VEGF)
Explanation:VEGF is produced by the endothelial cells and is the major growth factor responsible for causing vasculogenesis. Some isoforms of this growth factor also have a prominent role in formation of lymphatic vessels.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 42
Correct
-
The coronary sinus, which empties into the right atrium, serves to?
Your Answer: Drain the venous supply of the myocardium
Explanation:The coronary sinus is a collection of veins joined together to form a large vessel that collects blood from the heart muscle (myocardium). It delivers deoxygenated blood to the right atrium, as do the superior and inferior vena cava.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 43
Correct
-
Which of the following is NOT an effect of a positive inotropic agent on the heart?
Your Answer: It decreases the rate of rise in ventricular blood pressure during systole
Explanation:Inotropic agents increase the contractility of the heart as well as the rate of rise in ventricular blood pressure during systole, generating a greater pressure and increasing the stroke volume e.g. like catecholamines do.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 44
Incorrect
-
If both the noradrenergic and the cholinergic systems are blocked in the heart, the rate will be approximately:
Your Answer: 140/min
Correct Answer: 100/min
Explanation:The normal heart beat is about 70/min. This is due to a predominant parasympathetic activity. If sympathetic activity was unopposed the heart rate would have been 150/min. When both the noradrenergic and cholinergic systems are blocked the heart rate is 100/min. This is the normal firing rate of the SA node.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 45
Incorrect
-
A trauma victim who has been intubated is tachycardic, hypotensive, and has a poor urine output. You feel she is dehydrated and decide to use a central venous catheter to help you manage her. As part of this, you keep an eye on the waveform of central venous pressure (CVP). Which of the following cardiac cycle phases corresponds to the CVP waveform's 'a wave'?
Your Answer: Early diastole
Correct Answer: End diastole
Explanation:The pressure measured in the right atrium or superior vena cava is known as central venous pressure (CVP). In a spontaneously breathing subject, the usual CVP value is 0-8 cmH2O (0-6 mmHg). The structure of the CVP waveform is as follows: The CVP’s components are listed in the table below: Component of the waveform The cardiac cycle phase. mechanical event mechanical event Diastole Atrial contraction a wave C wave v wave Early systole The tricuspid valve closes and bulges Late Systole Filling of the atrium with systolic blood x descent y descent Mid systole Relaxation of the atrium Early diastole Filling of the ventricles at an early stage
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 46
Incorrect
-
The heart rate can be accelerated by:
Your Answer: Fever and expiration
Correct Answer: Exercise and thyroid hormones
Explanation:The firing of the SA node will increase due to exercises and as the thyroid hormone has a chronotropic effect on the heart, it too will result in an increase in the heart rate via stimulation of the adrenergic receptors of the heart. As during exercise the sympathetic nervous system is activated, it will directly have an positive chronotropic effect on the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 47
Correct
-
The hyperpolarization phase of pacemaker cells is dominated by ____ current.
Your Answer: K+
Explanation:The hyperpolarization phase is a continuation of the repolarization phase but the membrane potential dips below the resting membrane potential. This results due to the fact that the K+ channels take a longer time to close than the Na+ channels. Hence efflux of the K+ will result in hyperpolarization.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 48
Correct
-
Adrenergic stimulation will lead to myocyte relaxation via the following mechanisms
Your Answer: Increased phosphorylation of phosholamban
Explanation:Phosphorylation of phospholamban, which increases calcium ATPase activity and sequestration of calcium in the sarcoplasmic reticulum. An increased rate of relaxation is explained because cAMP also activates the protein phospholamban, situated on the membrane of the SR, that controls the rate of uptake of calcium into the SR. The latter effect explains enhanced relaxation (lusitropic effect).
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 49
Incorrect
-
Where would one normally find venous valves?
Your Answer: Intestine
Correct Answer: Saphenous vein
Explanation:The intima of the limb veins is folded at intervals to form venous valves that prevent retrograde flow. There are no valves present in the very small veins, the great veins, or the veins in the brain and viscera.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 50
Incorrect
-
What is the most common cardiac defect seen in patients with Down’s syndrome?
Your Answer: Ventricular septal defect
Correct Answer: Atrioventricular septal defect
Explanation:The rate of congenital heart disease in new-borns with Down syndrome is around 40%. Of those with heart disease, about 80% have an atrioventricular septal defect or ventricular septal defect with the former being more common. Mitral valve problems become common as people age, even in those without heart problems at birth.[3] Other problems that may occur include tetralogy of Fallot and patent ductus arteriosus.[38] People with Down syndrome have a lower risk of hardening of the arteries
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 51
Correct
-
Which of the following makes up the thick filaments?
Your Answer: Myosin
Explanation:The thick filaments are made up of myosin and the thin filaments are made up of actin. The thick filaments are twice the size of the thin filaments and are aligned to form the A band. The thin filaments extending out from the A band form the less dense I bands.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 52
Correct
-
In which area is depolarization initiated?
Your Answer: SA node
Explanation:SA node is the pacemaker of the heart. It determines the rate of contractions. It is the place where depolarization is initiated. It exhibits phase 4 depolarization or automaticity. Electrical impulses then spread to the AV node, purkinje fibers, bundle of his and the ventricular muscles.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 53
Correct
-
Which vaso metabolite decreases coronary blood flow?
Your Answer: Endothelin
Explanation:Decreased O2, increased CO2, lactate, prostaglandins, adenine nucleotides, adenosine, H+, K+ and cyanide produce vasodilation and thus an increase in coronary blood flow.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 54
Correct
-
During which phase of the cardiac cycle does most of the ventricular filling occur?
Your Answer: Ventricular diastole
Explanation:During the phase of ventricular diastole when the heart muscle relaxes and all the valves are open, blood flows easily into the heart. This is the phase of rapid ventricular filling. During isovolumetric contraction and relaxation the volume of blood in the heart does not change. During ventricular ejection blood enters into the aorta and pulmonary vessels.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 55
Correct
-
Which of the following conditions has no effect on cardiac output?
Your Answer: Sleep
Explanation:Sleep has no effect on the cardiac output. Anxiety, excitement and pregnancy will increase the cardiac output. Standing from a lying position will decrease the cardiac output transiently.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 56
Incorrect
-
What is pulse pressure?
Your Answer: 1/3 systolic plus 2/3 diastolic
Correct Answer: Difference between systolic and diastolic pressure
Explanation:The pulse pressure is the difference between the measured systolic and diastolic pressures.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 57
Incorrect
-
Which of the following structures is not part of the conducting system of the heart?
Your Answer: Internodal pathway
Correct Answer: Ventricular wall
Explanation:The conduction system of the heart consists of the SA node, AV node, internodal pathway between these two nodes, Bundle of His and the purkinje fibers
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 58
Incorrect
-
Which of the following is the most common causative organism in infective endocarditis?
Your Answer: Staphylococcus aureus
Correct Answer: Streptococcus viridans
Explanation:Viridans Alpha-haemolytic streptococci, that are present in the mouth are the most frequently isolated microorganisms when the infection is acquired in a community setting. In contrast, Staphylococcus blood stream infections are frequently acquired in a health care setting where they can enter the blood stream through procedures that cause break in the integrity of skin like surgery, catheterisation or during access of long term indwelling catheters or secondary to intravenous injection of recreational drugs.Prosthetic valve endocarditis is commonly caused by Staphylococcus epidermidis as it is capable of growing as a biofilm on plastic surfaces
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 59
Correct
-
Question 60
Incorrect
-
Which of the following is true of the Natriuretic hormones?
Your Answer: They are released in response to hypervolemia
Correct Answer:
Explanation:Natriuretic hormones are vasodilators released in response to hypervolemia
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 61
Correct
-
Arterioles stemming from the coronary artery can also empty into the heart directly via the:
Your Answer: Arteriosinusoidal vessels
Explanation:Most of the venous blood returns to the heart via the coronary sinus and the anterior cardiac veins. Apart from these there are other vessels that drain directly into the heart chambers. They include arteriosinusoidal vessels, which connect the arterioles to the heart chambers. The thebesian veins drain the capillaries into the chambers and the arterioluminal vessels drain small arteries directly into the chambers.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 62
Correct
-
Angina pectoris develops when the flow through the coronary artery becomes:
Your Answer: Oxygen deficient
Explanation:Angina pectoris develops when stenosis ( >70%) of the artery occurs as a result of formation of an atherosclerotic plaque. This leads to a decrease in the O2 carried to the thickened heart muscle by the blood, leading to the characteristic chest pain associated with angina pectoris.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 63
Incorrect
-
The areas of extensive series of sarcoplasmic folds known as intercalated discs always occur at what portion of the muscle fiber?
Your Answer: A band
Correct Answer: Z lines
Explanation:The muscle fibers of the heart branch and interdigitate, but one complete unit is surrounded by a cell membrane. The place where one muscle fiber abuts the other, the cell membrane of both the fibers run parallel to each other through a series of extensive folds. These areas always occur on the Z lines and are known as intercalated discs.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 64
Incorrect
-
Question 65
Correct
-
With regard to the endothelial structure, the epithelium constitute:
Your Answer: Simple squamous
Explanation:The single layer of squamous epithelium lining the heart and blood vessels is known as the endothelium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 66
Correct
-
Question 67
Incorrect
-
Describe the location of the SA node:
Your Answer: Posterior portion of the right interatrial septum
Correct Answer: Junction of the SVC and right atrium
Explanation:Anatomically the SA node is located at the junction of the superior vena cava and the right atrium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 68
Incorrect
-
Preload:
Your Answer: Is inversely proportional to the end-diastolic volume
Correct Answer: Is the degree to which the myocardium is stretched before is contracts
Explanation:Preload is end diastolic volume. It is the degree to which the heart muscle fiber is stretched when it fills up completely just before the heart contracts.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 69
Incorrect
-
What is the effect of catecholamines (i.e. increased heart rate) on the pressure volume loop?
Your Answer: Shifts the diastolic pressure curve to the right
Correct Answer: Shifts the diastolic pressure curve upward and leftward
Explanation:Catecholamines have a positive ionotropic and chronotropic effect on the heart. The ventricles develop greater tension during systole resulting in an increase in the stroke volume. The increase in stroke volume results in a decrease in the end diastolic volume. This pushes the loop towards the left and upwards.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 70
Correct
-
What type of intercellular connection found between cardiac muscle fibers allow for the spread of excitation from one cell to another?
Your Answer: Gap junctions
Explanation:The cardiac muscles have gap junctions in-between the cells. They form low resistance passages, which allow ions to diffuse through every muscle fiber rapidly and result in the cardiac muscles functioning as a syncytium, without any protoplasmic bridges involved.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 71
Correct
-
Question 72
Incorrect
-
The Sinoatrial node in the majority of people is supplied by the?
Your Answer: Left coronary artery
Correct Answer: Right coronary artery
Explanation:In 60% of people, the SA node is supplied by the right coronary artery branch and in 40% of the people by the left coronary artery.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 73
Correct
-
In ventricular fibrillation (VF), the first defibrillation attempt (with a biphasic defibrillator) should be made at:
Your Answer: 200 J
Explanation:Defibrillation is a common treatment for life-threatening cardiac dysrhythmias and ventricular fibrillation. If the patient is in Ventricular tachycardia (VT) or ventricular fibrillation (VF) on the monitor, immediately apply the pads and shock the patient with 120-200 Joules on a biphasic defibrillator or 360 Joules on a monophasic defibrillator.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 74
Incorrect
-
The steps of cardiac cycle in sequence are:
Your Answer: Isovolumetric relaxation, isovolumetric contraction, ejection, passive ventricular filling, active ventricular filling
Correct Answer: Isovolumic contraction, ejection, isovolumic relaxation, passive ventricular filling, active ventricular filling.
Explanation:The cardiac cycle refers to a complete heartbeat from its generation to the beginning of the next beat, and so includes the diastole, the systole, and the intervening pause.1st stage: diastole, or passive filling is when the semilunar valves (the pulmonary valve and the aortic valve) close, the atrioventricular (AV) valves (the mitral valve and the tricuspid valve) open, and the whole heart is relaxed. 2nd stage: atrial systole, is when the atrium contracts, and blood flows from atrium to the ventricle (active filling).3rd stage: isovolumic contraction is when the ventricles begin to contract, the AV and semilunar valves close, and there is no change in volume. 4th stage: ventricular ejection, is when the ventricles are contracting and emptying, and the semilunar valves are open. 5th stage: isovolumic relaxation time, pressure decreases, no blood enters the ventricles, the ventricles stop contracting and begin to relax, and the semilunar valves close due to the pressure of blood in the aorta.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 75
Correct
-
What is a characteristic findings on ECG in hyperkalaemia?
Your Answer: Tall, tented T waves
Explanation:Hyperkalaemia leads to:- Prolonged PR interval- Small P waves- Tall, tented T waves – Widened QRS complexes and eventually asystole.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 76
Incorrect
-
Which coronary artery supplies the right atria?
Your Answer: Left coronary
Correct Answer: Right coronary
Explanation:The left coronary artery distributes blood to the left side of the heart, the left atrium and ventricle, and the interventricular septum. The circumflex artery arises from the left coronary artery and follows the coronary sulcus to the left. Eventually, it will fuse with the small branches of the right coronary artery. The right coronary artery proceeds along the coronary sulcus and distributes blood to the right atrium, portions of both ventricles, and the heart conduction system.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 77
Incorrect
-
Which of the following normally has a slow depolarizing “prepotential”?
Your Answer: Purkinje fibers
Correct Answer: Sinoatrial node
Explanation:There are 2 main types of action potentials (AP) in the heart, the slow response and the fast response:The slow response is initiated by the slow calcium-sodium channels, found in the SA node (which is the natural pacemaker of the heart) and the conduction fibers of the AV node.The fast response occurs in the atrial and ventricles muscle cells and the purkinje fibers.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 78
Incorrect
-
Transport of Ca2+ into the reticulum to initiate cardiac muscle relaxation in via:
Your Answer: Voltage-gated Ca2+ channels
Correct Answer: Serca (sarcoplasmic or endoplasmic reticulum Ca2+ ATPase)
Explanation:Phosphorylation of phospholamban, which increases calcium ATPase activity and sequestration of calcium in the sarcoplasmic reticulum. An increased rate of relaxation is explained because cAMP also activates the protein phospholamban, situated on the membrane of the SR, that controls the rate of uptake of calcium into the SR. The latter effect explains enhanced relaxation (lusitropic effect).
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 79
Incorrect
-
In Starling’s law of the heart, the decrease in tension developed by muscle contraction at high degrees of stretch is due to:
Your Answer: A decrease in the number of cross bridges between myosin and actin
Correct Answer: Disruption of myocardial fibers
Explanation:Starling law states that the force of contraction is directly proportional to the preload. When the heart muscle is stretched beyond its limit the tension that is developed decreases, this is not due to loss of formation of effective myosin and actin cross bridges. The heart muscles despite being fully stretched is never stretched to this point. The reason for this decreased tension is physical disruption of the myocardial fibers.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 80
Incorrect
-
Which is the most common site for primary cardiac tumours to occur in adults?
Your Answer: Left ventricle
Correct Answer: Left atrium
Explanation:Myxomas are the most common type of primary heart tumour. The tumour is derived from multipotential mesenchymal cells and may cause a ball valve-type obstruction. About 75% of myxomas occur in the left atrium of the heart, usually beginning in the wall that divides the two upper chambers of the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 81
Incorrect
-
The positive inotropic effect of digoxin is due to?
Your Answer: Stimulation of calcium channels
Correct Answer: Inhibition of the sodium potassium ATPase in the myocardium
Explanation:Digitalis compounds are potent inhibitors of cellular Na+/K+-ATPase. This ion transport system moves sodium ions out of the cell and brings potassium ions into the cell. By inhibiting the Na+/K+-ATPase, cardiac glycosides cause the intracellular sodium concentration to increase. This then leads to an accumulation of intracellular calcium via the Na+/Ca++ exchange system. In the heart, increased intracellular calcium causes more calcium to be released by the sarcoplasmic reticulum, thereby making more calcium available to bind to troponin-C, which increases contractility (inotropy).
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 82
Incorrect
-
Absolute refractory period in a cardiac action potential graph occurs during.
Your Answer: Plateau phase
Correct Answer: All of the above
Explanation:Absolute refractory period (ARP): the cell is completely unexcitable to a new stimulus and occurs from phase 0 – 2 i.e. depolarisation, early repolarisation and plateau phase.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 83
Incorrect
-
Cross-bridges between actin and myosin filaments contain:
Your Answer: ATPase
Correct Answer: Calcium ions
Explanation:At rest troponin I is bound to actin and tropomyosin and covers the site where the myosin head interacts with actin. When calcium enters into the muscle, it binds with troponin C and causes a structural change in troponin I which moves out of the myosin binding site and causes the cross bridges between the actin and myosin filaments to occur.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 84
Incorrect
-
Blood flow to the subendocardial portions of the left ventricular muscle occurs mainly during:
Your Answer: Systole
Correct Answer: Diastole
Explanation:The sub endocardium receives the least amount of blood from the coronary arteries. During systole the coronary arteries collapse as a result of the pressure from contraction that is exerted on them. During diastole the heart muscle relaxes and the pressure on the coronary vessels is relieved allowing blood to flow through them to the sub endocardium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 85
Incorrect
-
You've been requested to give a discussion to a group of medical students about cardiovascular physiology. One of them inquires about cardiac output and asks if you can explain it. Which of the following statements is correct?
Your Answer: An average resting cardiac output in a man is 4 L/min
Correct Answer: An average resting cardiac output in a woman is 5 L/min
Explanation:The terminology cardiac output refers to the amount of blood pumped by the heart in one minute. Women’s rates are around 5 L/min, whereas men’s rates are somewhat higher, around 5.5 L/min. Cardiac output (CO) is calculated by multiplying stroke volume (SV) by heart rate (HR): CO = HR x SV As a result, both stroke volume and heart rate are exactly proportional to cardiac output. There will be an increase in cardiac output if the stroke volume or heart rate increases, and a reduction in cardiac output if the stroke volume or heart rate lowers.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 86
Correct
-
Initial depolarization of cardiac muscle is due to influx of:
Your Answer: Na+
Explanation:Initial depolarization of the cardiac muscle results from opening of the sodium voltage gated channels. This results in the influx of sodium and an increase in the membrane potential towards threshold. Potassium efflux results in repolarization.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 87
Incorrect
-
The following contributes to the rate of depolarization?
Your Answer: Hypoxia
Correct Answer: All of the above
Explanation:Depolarization occurs due to impulses generated by the SA node. As the heart beats to the rhythm of the SA node, certain factors will effect the rate of depolarization. All the above mentioned options effect the rate of depolarization.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 88
Incorrect
-
Which of the atrial pressure changes represents the a-wave of the JVP
Your Answer: Ventricular systole
Correct Answer: Atrial systole
Explanation:The a-wave created on the venous pulse curve occurs as a result of atrial systole. Due to the pressure build-up in the atria, it causes a back pressure in the vena cava. This pressure is exerted on the valve and this back pressure is what causes a slight increase in the venous pressure.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 89
Correct
-
Question 90
Correct
-
Question 91
Correct
-
Which of the following corresponds to an oblique line drawn from the sternal end of the left 3rd costal cartilage to the sternal end of the right 6th costal cartilage?
Your Answer: Atrio-ventricular (coronary) groove
Explanation:The AV groove corresponds to the right border of the heart. The right border corresponds to a line drawn from the 3rd right costal cartilage to the 6th right costal cartilage; this border is slightly convex to the right.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 92
Correct
-
Which of the following is true with AV nodal delay?
Your Answer: Shortened by sympathetic stimulation
Explanation:AV nodal delay Is about 0.1s before the action potential spreads to the ventricles. It is shortened by stimulation of the sympathetic nervous system and lengthened by stimulation of the parasympathetic system.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 93
Incorrect
-
Excitation-contraction coupling in cardiac muscle involves all of the following except:
Your Answer: ATP hydrolysis
Correct Answer: Binding of Ca2+ to calmodulin
Explanation:In the excitation contraction coupling model, an action potential is transmitted to the fibrils of a fiber through the T tubule system. It triggers the release of Ca 2+ from the terminal cisterns. Depolarization of the T tubules activates the sarcoplasmic reticulum through the dihydropyridine receptors. These are voltage gates calcium channels. Calcium binds to calmodulin during contraction of the smooth muscle and not the cardiac muscles.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 94
Correct
-
Vasodilatation in skeletal muscle can be caused by:
Your Answer: Sympathetic cholinergic nerves
Explanation:In skeletal muscles some fibers that cause vasodilation run with the nerves of the sympathetic system but are cholinergic in nature. These nerves are not active during rest but become active during exercise and stress.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 95
Correct
-
Which of the following occurs during a Valsalva manoeuvre?
Your Answer: An initial rise in blood pressure
Explanation:The Valsalva manoeuvre is forced expiration against a closed glottis with increased intrathoracic pressure throughout and an initial rise in blood pressure. There is no disruption of autonomic function.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 96
Incorrect
-
Cholinergic vagal supply to the SA and AV nodes results in slowing of the heart rate via:
Your Answer: M1 muscarinic receptors
Correct Answer: M2 muscarinic receptors
Explanation:M2 muscarinic receptors are the receptors for the parasympathetic system to the SA and the AV node.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 97
Correct
-
Question 98
Correct
-
The direct determinants of cardiac output are
Your Answer: Stroke volume and heart rate
Explanation:Cardiac output is classically defined alongside stroke volume (SV) and the heart rate (HR) as:Cardiac Output [L/min] = Stroke Volume [L/beat] x Heart Rate [beats/min]
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 99
Correct
-
Myocardium requires more oxygen to expel blood in:
Your Answer: A stenotic aortic valve
Explanation:In aortic valve stenosis, increased ventricular pressure Is needed to expel the blood into the aorta. Increased pressure means increased contractility hence increase O2 consumption by the heart muscles.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 100
Correct
-
The basic unit of contraction in myocytes is:
Your Answer: Sarcomere
Explanation:Sarcomere is the organelle where calcium is stored to be released during contraction of the muscle. It is the basic unit of contraction in striated muscle fibers. As myocytes are also striated muscles, sarcomeres also forms the basic unit of contraction. The impulses travel along the membrane and via its interaction with the dihydropyridine receptors it releases the stored calcium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 101
Incorrect
-
Where would one find pericytes around endothelial cells?
Your Answer: Smaller arteries
Correct Answer: Post-capillary venules
Explanation:Pericytes release a wide variety of vasoactive agents which regulate the flow through the junction between endothelial cells.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 102
Correct
-
Question 103
Incorrect
-
In the blood supply of the heart, ‘dominance’ refers to the coronary artery which supplies the?
Your Answer: Right atrium
Correct Answer: Posterior interventricular artery
Explanation:Dominance of the coronary artery system is defined by the artery that gives rise to the posterior interventricular artery. Dominance of the right coronary artery is more common (68%). It gives rise to the large posterior interventricular branch which goes down to the apex of the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 104
Correct
-
Which of the following affects the magnitude of the action potential?
Your Answer: Changes in the external Na+ concentration
Explanation:The magnitude of the action potential is determined by the sodium current. Increase in external sodium will result in increased influx of sodium and hence generation of a stronger action potential.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 105
Correct
-
The process by which depolarization of the muscle fiber initiates contraction is called?
Your Answer: Action potential
Explanation:This process is known as an action potential. Upon generation of an action potential when depolarization reaches threshold, it spreads throughout the muscle fiber, resulting in generation of an excitation-contraction coupling leading to contraction of the muscle.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 106
Incorrect
-
Hyperkalaemia [K+ =7meq/l] can lead to the following ECG changes [Ca++ normal]
Your Answer: QRS lengthened
Correct Answer: Peaked T waves
Explanation:Hyperkalaemia causes the formation of tall tented T waves due to altered repolarization.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 107
Incorrect
-
Xanthines such as caffeine and theophylline are positively inotropic due to:
Your Answer: Circulating catecholamines
Correct Answer: Inhibition of cAMP breakdown
Explanation:Xanthines exert their positive inotropic effect by inhibiting the breakdown of the cAMP resulting in stronger and sustained contractions.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 108
Correct
-
Which of the following concerning PR interval is INCORRECT?
Your Answer: Always measured from the beginning of p wave to the beginning of r wave
Explanation:The PR interval measures the time from the start of atrial depolarization to the start of ventricular depolarization. The PR interval is only measured from the beginning of P wave to beginning of R wave if the Q wave is absent.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 109
Incorrect
-
Which of the following factors serve to decrease cardiac output?
Your Answer: Anxiety
Correct Answer: Standing from a lying position
Explanation:Sleep has no effect on the cardiac output. Anxiety, excitement, increased body temperature and pregnancy will increase the cardiac output. Standing from a lying position will decrease the cardiac output transiently.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 110
Incorrect
-
Myocyte action potentials – Choose the false statement:
Your Answer: Depolarisation spreads rapidly through the individual fibers due to the presence of gap junctions
Correct Answer: Repolarisation is due to net k+ influx
Explanation:Final repolarization (phase 3) to the resting membrane potential (phase 4) is due to closure of the Ca2+ channels and a slow, delayed increase of K+ efflux through various types of K+ channels.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 111
Incorrect
-
Concerning coronary arteries, what is the net effect of B2 stimulation on the heart (e.g. Running athlete)?
Your Answer: Vasoconstriction via production of metabolites
Correct Answer: Vasodilation via production of metabolites
Explanation:The coronary arterioles contain α-adrenergic receptors, which cause vasoconstriction, and β-adrenergic receptors, which cause vasodilation. Activity in the noradrenergic nerves to the heart and injections of norepinephrine cause coronary vasodilation. However, norepinephrine also increases the heart rate and the force of cardiac contraction, and the vasodilation is due to production of vasodilator metabolites in the myocardium secondary to the increase in its activity. As exercise has the same effect as sympathetic stimulation, it will result in vasodilation.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 112
Incorrect
-
Concerning surface anatomy, where is the base of the heart
Your Answer: 5th intercostal space mid clavicular line
Correct Answer: 2nd left costal to 3rd right costal cartilage
Explanation:The base of the heart, also known as the superior border of the heart corresponds to a line connecting the inferior border of the 2nd left costal cartilage to the superior border of the 3rd right costal cartilage.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 113
Incorrect
-
Question 114
Incorrect
-
Question 115
Incorrect
-
The T-tubular system in cardiac muscle is:
Your Answer: Has serca molecules that pump Ca2+ into the SR to initiate muscle relaxation
Correct Answer: Transmits action potential from sarcolemma to the SR to allow for Ca2+ release into the cytoplasm
Explanation:Action potentials are transmitted to the fibrils of a fiber through the T tubule system. It triggers the release of Ca 2+ from the terminal cisterns. Depolarization of the T tubules activates the sarcoplasmic reticulum through the dihydropyridine receptors, which are voltage gated calcium channels.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 116
Correct
-
Troponin I is inhibited by calcium binding to:
Your Answer: Troponin c
Explanation:At rest troponin I is bound to actin and tropomyosin and covers the site where the myosin head interacts with actin. When calcium enters into the muscle, it binds with troponin C and cause a structural change in troponin I which moves out of the myosin binding site and causes the cross bridges between the actin and myosin filaments to occur.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 117
Correct
-
The principle by which the energy of contraction is proportional to the initial length of cardiac muscle fiber is known as:
Your Answer: Starling’s law
Explanation:The Frank starling relationship describes that an increase in the venous return or the end diastolic volume will cause an increase in the stroke volume/ preload and also cardiac output. It stems from the fact that increase venous return will increase the stretch on the ventricular muscle fibers. The sarcomere will stretch a considerable length that is needed for maximum contraction and increased development of tension in the muscle fiber. The greater the venous return the greater the cardiac output. This relation is directly proportional.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 118
Correct
-
The coronary sinus drains into the:
Your Answer: Right atrium
Explanation:The coronary sinus drains into the right atrium. Most of the venous blood returns to the heart via the coronary sinus and the anterior cardiac veins. Apart from these there are other vessels that drain directly into the heart chambers.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 119
Incorrect
-
Coronary vasoconstriction can be caused by:
Your Answer: Vagal tone
Correct Answer: Beta blockage
Explanation:Coronary arteries contain alpha and beta receptors. The alpha receptor stimulates vasoconstriction and beta receptors stimulate vasodilation. When the chronotropic and inotropic effects of noradrenergic receptors are blocked by a B blocking drug, stimulation of the noradrenergic nerves will cause coronary vasoconstriction.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 120
Incorrect
-
In the Fick‘s method of measuring cardiac output, the arterial oxygen content can be measured in a sample obtained from
Your Answer: The aorta
Correct Answer: The pulmonary vein
Explanation:In Fick’s original method, the following variables are measured:VO2, oxygen consumption in ml of pure gaseous oxygen per minute. This may be measured using a spirometer within a closed rebreathing circuit incorporating a CO2 absorberCa, the oxygen concentration of blood taken from the pulmonary vein (representing oxygenated blood)Cv, the oxygen concentration of blood from an intravenous cannula (representing deoxygenated blood)From these values, we know that:VO2 = (CO x Ca) – (CO x Cv)where CO = Cardiac Output, Ca = Oxygen concentration of arterial blood and Cv = Oxygen concentration of mixed venous blood.This allows us to sayCO = VO2/{Ca – Cv}and hence calculate cardiac output.Note that (Ca – Cv) is also known as the arteriovenous oxygen difference.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 121
Incorrect
-
Myocardial oxygen consumption is increased by:
Your Answer: B[ an increase in preload
Correct Answer: An increase in after load
Explanation:Cardiac oxygen consumption is directly related to the amount of tension that develops in the ventricles. It is increased by an increased size of heart, increased afterload, increased contractility and increased heart rate.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 122
Correct
-
The following is true in relation to coronary venous drainage?
Your Answer: Most venous return ultimately drains into right atrium via the coronary sinus
Explanation:Most of the venous blood returns to the heart via the coronary sinus and the anterior cardiac veins. Apart from these there are other vessels that drain directly into the heart chambers
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 123
Incorrect
-
Select the correct statement regarding the 4th heart sound, it?
Your Answer: Occurs during isovolumetric ventricular contraction.
Correct Answer: Can be heard in atrial systole.
Explanation:The fourth heart sound is not normally audible in a normal adult. It occurs as a consequence of ventricular hypertrophy. It is caused by filling of the ventricle by atrial systole.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 124
Incorrect
-
The branche(s) of the left coronary artery are
Your Answer: Anterior interventricular artery
Correct Answer: A and b
Explanation:Posterior descending artery comes from Right coronary artery. The anterior interventricular artery is otherwise known as the anterior descending branch.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 125
Incorrect
-
Which of the following is a method for measurement of cardiac output?
Your Answer: Starling method
Correct Answer: Indicator dilution method
Explanation:There are two methods of calculating the cardiac output in humans other than doppler with echocardiography: The direct Fick’s method and the indicator dilution method. In the indicator dilution technique, a known amount of a substance such as a dye or, more commonly, a radioactive isotope is injected into an arm vein and the concentration of the indicator in serial samples of arterial blood is determined. The output of the heart is equal to the amount of indicator injected divided by its average concentration in arterial blood after a single circulation through the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 126
Incorrect
-
The celiac trunk consists of which arteries?
Your Answer: Left gastric, common hepatic, phrenic
Correct Answer: Left gastric, common hepatic, splenic
Explanation:The celiac trunk is the first major branch of the abdominal aorta. It is 1.25 cm in length. Branching from the aorta at thoracic vertebra 12 (T12). There are three main divisions of the celiac artery:- left gastric artery- common hepatic artery- splenic artery
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 127
Incorrect
-
Where on the surface of the chest is the normal site of auscultation for the mitral area?
Your Answer: 4th left intercostal space anterior axillary line
Correct Answer: 4th left intercostal space in the mid-clavicular line
Explanation:The mitral valve is situated in the left 4th intercostal space just beneath the sternum, in the mid clavicular line.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 128
Incorrect
-
In a 30 year old male with hypertrophic obstructive cardiomyopathy (HOCM), which of the following is associated with increased risk of sudden death?
Your Answer: Family history of sudden death
Correct Answer: Degree of left ventricular hypertrophy
Explanation:Hypertrophic cardiomyopathy (HCM) is a disease in which a portion of the myocardium (heart muscle) is enlarged without any obvious cause, creating functional impairment of the heart. It is the leading cause of sudden death in young athletes. Major risk factors for sudden death in individuals with HCM include prior history of cardiac arrest or ventricular fibrillation, spontaneous sustained ventricular tachycardia, family history of premature sudden death, unexplained syncope, left ventricular thickness greater than or equal to 30 mm, abnormal exercise blood pressure and unsustained ventricular tachycardia. The most strongly correlated is the degree of left ventricular hypertrophy (LVH).
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 129
Incorrect
-
The bradycardia that occurs in patients with raised intracranial pressure is a result of the?
Your Answer: Autoregulation
Correct Answer: Cushing reflex
Explanation:When intracranial pressure is increased, the blood supply to RVLM neurons is compromised. This results in an increase in their discharge as a result of hypoxia and hypercapnia. The resultant rise in systemic arterial pressure (Cushing reflex) tends to restore the blood flow to the medulla.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 130
Incorrect
-
When the heart rate is increased (to pathological levels) which of the following is correct when comparing the duration of diastole to systole?
Your Answer: It can be both shorter and longer
Correct Answer: It is shortened to a greater degree
Explanation:The duration of systole is more fixed than the duration of diastole. When the heart rate increases the timing of the systole remains more or less the same however diastole decreases.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 131
Incorrect
-
Which of the following intercellular connections is important in endothelial barrier function?
Your Answer: Desmosomes
Correct Answer: Tight junctions
Explanation:Tight junctions surround the apical margins of the epithelial cells such as in the intestinal mucosa and the choroid plexus. They are also important to the endothelial barrier function. They are made up of ridges that adhere to each other strongly at the cell junction, obliterating the space completely between the cells.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 132
Incorrect
-
What percentage of the cardiac output is delivered to the brain?
Your Answer: 35%
Correct Answer: 15%
Explanation:Among all body organs, the brain is most susceptible to ischaemia. Comprising of only 2.5% of total body weight, the brain receives 15% of the cardiac output. Oxygen extraction is also higher with venous oxygen levels approximating 13 vol%, and arteriovenous oxygen difference of 7 vol%.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 133
Incorrect
-
When does the heart rate decrease?
Your Answer: After a meal
Correct Answer: Pressure on the eyeball
Explanation:Various vagotonic manoeuvres (e.g. Valsalva manoeuvre, carotid sinus massage, pressure on eyeballs, ice-water facial immersion, swallowing of ice-cold water) result in increased parasympathetic tone through the vagus nerve which results in a decrease in heart rate. These manoeuvres may be clinically useful in terminating supraventricular arrhythmias.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 134
Correct
-
AV valves open during?
Your Answer: Early diastole
Explanation:The cardiac cycle refers to a complete heartbeat from its generation to the beginning of the next beat, and so includes the diastole, the systole, and the intervening pause.The first stage, diastole, is when the semilunar valves (the pulmonary valve and the aortic valve) close, the atrioventricular (AV) valves (the mitral valve and the tricuspid valve) open, and the whole heart is relaxed. The second stage, atrial systole, is when the atrium contracts, and blood flows from atrium to the ventricle.The third stage, isovolumic contraction is when the ventricles begin to contract, the AV and semilunar valves close, and there is no change in volume. The fourth stage, ventricular ejection, is when the ventricles are contracting and emptying, and the semilunar valves are open. During the fifth stage, isovolumic relaxation time, pressure decreases, no blood enters the ventricles, the ventricles stop contracting and begin to relax, and the semilunar valves close due to the pressure of blood in the aorta.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 135
Correct
-
Following an action potential, cytosolic Ca2+ is increased. The binding of free Ca2+ to troponin C results in all of the following except:
Your Answer: Weakening of the troponin i interaction with actin
Explanation:At rest, troponin i is bound to actin and tropomyosin and covers the site where the myosin head interacts with actin. When Calcium enters into the muscle, it binds with troponin C and cause a structural change in troponin i which moves out of the myosin binding site and causes the cross bridges between the actin and myosin filaments to occur.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 136
Correct
-
Where does the SA node develop?
Your Answer: From structures on the right side of the embryo.
Explanation:The SA node develops from the right side of the embryo and the AV node from the left. This is the reason why in adults the right vagus supplies the SA node and the left vagus supplies the AV node.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 137
Incorrect
-
Which of the following is NOT associated with the development of aortic regurgitation?
Your Answer: Syphilis
Correct Answer: Dilated cardiomyopathy
Explanation:Aortic insufficiency, is often due to the aortic root dilation, which is idiopathic in over 80% of cases, but otherwise may result from aging, syphilitic aortitis, osteogenesis imperfecta, aortic dissection, Bechet’s disease, reactive arthritis and systemic hypertension. Additionally, aortic insufficiency has been linked to the use of some medications and other potential causes that affect the valve directly including Marfan’s syndrome, Ehlers–Danlos syndrome, ankylosing spondylitis, and systemic lupus erythematosus. In acute cases of aortic insufficiency, the main causes are infective endocarditis, aortic dissection or trauma. Dilated cardiomyopathy is associated with the development of mitral regurgitation, not aortic regurgitation
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 138
Incorrect
-
Which one of the following ECG findings is least associated with digoxin use?
Your Answer: Bradycardia
Correct Answer: Prolonged QT interval
Explanation:Digoxin ECG features:• ST depression (‘reverse tick’)• flattened/inverted T waves• Prolonged PR interval• short QT interval• arrhythmias e.g. AV block, bradycardia, ventricular tachycardia or fibrillation (for example paroxysmal atrial tachycardia with A-V block – so-called PAT with block) is said to be pathognomonic (i.e. diagnostic) of digoxin toxicity.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 139
Incorrect
-
Which of the following causes the closure of the ductus arteriosus during birth?
Your Answer: Increased left atrial pressure
Correct Answer: Reduced levels of prostaglandins
Explanation:Ductus arteriosus is kept open by the prostaglandin E2 which is a vasodilator. At birth the high levels of cyclooxygenase blocks the production of prostaglandins which results in the closure of the ductus arteriosus.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 140
Correct
-
In which organ will you find extremely porous sinusoidal capillaries, with discontinuous endothelium?
Your Answer: Liver
Explanation:The liver is the organ which contains sinusoidal capillaries with discontinuous endothelium. The brain, lungs and the intestine all contain continuous capillaries, however the kidney contains fenestrated capillaries to aid in filtration.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 141
Incorrect
-
The function of ATP in cardiac muscle contraction includes:
Your Answer: Act as a ligand for serca pump to allow for Ca2+ re-sequestration in the sarcoplasmic reticulum
Correct Answer: Binding to myosin after the power stroke to allow uncoupling of actin and myosin
Explanation:After calcium binds to the troponin C, there is a conformational change in the structure of troponin I and tropomyosin, which moves out of the way and frees the site where myosin can bind to actin. This results in the formation of the cross linkage of the actin and myosin giving rise to the power stroke in the contraction phase. This occurs with the release of ADP. When ATP combines to this complex it breaks and the cycle repeats itself.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 142
Incorrect
-
Regarding cardiac contractility, catecholamines exert their inotropic effect via:
Your Answer: Myocardial Na+/K+ ATPase
Correct Answer: Β1-adrenergic receptors and gs
Explanation:Catecholamines exert their inotropic effect on the heart via the B1 adrenergic receptors and Gs, stimulating adenyl cyclase and increasing the production of cAMP.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 143
Incorrect
-
Xanthines (for example Caffeine), exhibit their positive inotropic effect by:
Your Answer: Stimulation of b1-adrenergic receptors
Correct Answer: Inhibiting the breakdown cAMP
Explanation:Xanthines exert their positive inotropic effect by inhibiting the breakdown of the cAMP resulting in stronger and sustained contraction.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 144
Incorrect
-
Which of the following suggests the presence of mitral regurgitation as well as mitral stenosis?
Your Answer: Loud P2
Correct Answer: Displaced apex beat
Explanation:Mitral stenosis on its own does not lead to left ventricular dilatation and hence a displaced apex beat. Thus a displaced apex beat is suggestive of mixed mitral disease. The other options occur in mitral stenosis.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 145
Incorrect
-
The isoforms of nitric oxide synthase which are found in the nervous system (NOS1) and endothelial cells (NOS3) are activated by agents that increase which of the following intracellular electrolytes?
Your Answer: Na
Correct Answer: Ca
Explanation:Synthesis of nitric oxide is stimulated by activation of the NMDA receptors by certain agents. This leads to opening of the Calcium channels and an influx of calcium into the cell. This will activate the nitric oxide synthase. Nitric oxide is produced on demand.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 146
Incorrect
-
Which of the following statements is true regarding pulsus alternans?
Your Answer: The pulse is irregular
Correct Answer: It is found in association with a third heart sound
Explanation:Pulsus alternans is a physical finding with arterial pulse waveform showing alternating strong and weak beats. It is almost always indicative of left ventricular systolic impairment, and carries a poor prognosis. A pathological third heart sound is usually associated.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 147
Incorrect
-
The interventricular septum is supplied anteriorly by the?
Your Answer: Posterior descending artery
Correct Answer: Left anterior descending artery
Explanation:The anterior interventricular artery or left anterior descending artery supplies the anterior 2/3rds of the interventricular septum.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 148
Correct
-
Which of the following is NOT true of the parasympathetic control of the heart?
Your Answer: It can be blocked by beta blockers
Explanation:Parasympathetic fibers do not innervate the Beta receptors on the heart. They are innervated by the sympathetic nerve fibers. Then a beta blocker such as propranolol will block the sympathetic outflow and increase the parasympathetic tone of the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 149
Incorrect
-
Digoxin causes:
Your Answer: Hyperkalaemia
Correct Answer: Increase in cytosolic calcium concentration
Explanation:Digoxin is a positive inotrope which inhibits NA/K ATPase, increases cardiac contractility and can cause hypokalaemia.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 150
Correct
-
The coronary arteries fill during?
Your Answer: Diastole
Explanation:During systole the coronary arteries collapse as a result of the pressure due to contraction that is exerted on them. During diastole the heart muscle relaxes and the pressure on the coronary vessels is relieved allowing blood to flow through them to the subendocardium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 151
Correct
-
What is troponin?
Your Answer: A component of thin filaments
Explanation:Skeletal muscle cytoplasmic proteins include myosin and actin (also known as thick and thin filaments, respectively) which are arranged in a repeating unit called a sarcomere. Troponin is a component of thin filaments (along with tropomyosin), and is the protein to which calcium binds.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 152
Correct
-
Question 153
Incorrect
-
Which of the following components regulate cardiac output?
Your Answer: Autonomic nervous system
Correct Answer: All of the above
Explanation:Cardiac output is regulated by the autonomic nervous system with sympathetic nerves having a positive chronotropic and inotropic effect and parasympathetic nerves having the opposite effect. An increase in preload will increase cardiac output likewise an afterload increase will also increase cardiac output.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 154
Incorrect
-
The rate of depolarisation of the sinus node membrane potential is modulated by all the following except:
Your Answer: Hypoxia
Correct Answer: Cardiac output
Explanation:Cardiac output has no effect on the depolarization of the pacemaker potential of the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 155
Incorrect
-
How does pregnancy affect the cardiac output of a patient?
Your Answer: Decreased cardiac output due to decrease in stroke volume
Correct Answer: Increased cardiac output due to increase in heart rate and stroke volume
Explanation:Cardiac Output increases to a similar degree as the blood volume. During the first trimester cardiac output is 30-40% higher than in the non-pregnant state. Steady rises are shown on Doppler echocardiography, from an average of 6.7 litres/minute at 8-11 weeks to about 8.7 litres/minute flow at 36-39 weeks; they are due, primarily, to an increase in stroke volume (35%) and, to a lesser extent, to a more rapid heart rate (15%). There is a steady reduction in systemic vascular resistance (SVR) which contributes towards the hyperdynamic circulation observed in pregnancy
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 156
Incorrect
-
Concerning surface anatomy, where is the aortic valve found?
Your Answer: Situated in the left second intercostal space underneath the sternum
Correct Answer: Situated in the left third intercostal space underneath the sternum
Explanation:The aortic valve is situated in the left 3rd intercostal space just beneath the sternum.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 157
Incorrect
-
Depolarization of the T tubule membrane activates the sarcoplasmic reticulum via which receptors?
Your Answer: M 2 receptors
Correct Answer: Dihydropyridine receptors
Explanation:Action potentials are transmitted to the fibrils of a fiber through the T tubule system. It triggers the release of Ca 2+ form the terminal cisterns. Depolarization of the T tubules activates the sarcoplasmic reticulum through the dihydropyridine receptors. They are voltage gated calcium channels.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 158
Incorrect
-
In the jugular venous pressure wave…
Your Answer: ‘v’ wave coincide with rapid ventricular filling phase
Correct Answer: Consists of 3 peaks and 2 troughs
Explanation:The jugular venous pressure (JVP, sometimes referred to as jugular venous pulse) is the indirectly observed pressure over the venous system via visualization of the internal jugular vein. It can be useful in the differentiation of different forms of heart and lung disease. Classically three upward deflections (peaks) and two downward deflections (troughs) have been described:The upward deflections are the a (atrial contraction), c (ventricular contraction and resulting bulging of tricuspid into the right atrium during isovolumetric systole) and v = venous filling.The downward deflections of the wave are the x (the atrium relaxes and the tricuspid valve moves downward) and the y descent (filling of ventricle after tricuspid opening).
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 159
Incorrect
-
What is the normal duration of PR interval on an electrocardiogram of a healthy individual?
Your Answer: 0.01 0 0.10 s
Correct Answer: 0.12–0.20 s
Explanation:PR interval extends from the beginning of the P-wave until the beginning of the QRS complex. The normal duration of the PR interval is 0.12-0.20 s. It can be prolonged in first degree heart block, and reduced in Wolff-Parkinson-White syndrome.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 160
Incorrect
-
Relaxation of the cardiac muscle at the actin-myosin cross bridges is initiated by binding of which molecule to the exposed site on the myosin.
Your Answer: Calcium ATPase
Correct Answer: ATP
Explanation:A crossbridge is a myosin projection, consisting of two myosin heads, that extends from the thick filaments. Each myosin head has two binding sites: one for ATP and another for actin. The binding of ATP to a myosin head detaches myosin from actin, thereby allowing myosin to bind to another actin molecule. Once attached, the ATP is hydrolysed by myosin, which uses the released energy to move into the cocked position whereby it binds weakly to a part of the actin binding site.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 161
Incorrect
-
The postextrasystolic potentiation of myocardial contractility is due to:
Your Answer: Increase in cardiac rate
Correct Answer: Increase in intracellular Ca2+
Explanation:The postextrasystolic potentiation of myocardial contractility Is not due to ventricular filling. It occurs in isolated locations in the heart and is due to increase availability of intracellular calcium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 162
Correct
-
Regarding the myofilament molecules, which of the following contains binding sites for calcium that helps to initiate contraction?
Your Answer: Troponin c
Explanation:Troponin T binds the troponin components to tropomyosin. Troponin I inhibits the interaction of myosin with actin and troponin C contains the binding sites for the Ca2+ that helps initiate contraction.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 163
Incorrect
-
Which of the following structures of the cardiac conduction system is located in the right posterior portion of the interatrial septum?
Your Answer: SA node
Correct Answer: AV node
Explanation:AV node is located at the right posterior portion of the interatrial septum.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 164
Correct
-
Which ion channel does not contribute to the myocardial action potential?
Your Answer: Chloride channel
Explanation:The upstroke in the cardiac action potential is due to opening of the sodium channels and an influx of sodium into the cell. The initial repolarization phase is due to transient opening of the potassium channels along with calcium channels. Influx of calcium causes the prolonged plateau phase of the action potential. Delayed opening of the rectifier potassium channel and delayed closure of the calcium channel leads to the repolarization phase of cardiac action potential.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 165
Incorrect
-
Which of the following phases in depolarization and repolarization of cardiac muscle cells are caused by the inactivation of Na+ channels?
Your Answer: Phase 2 : plateau
Correct Answer: Phase 1 : rapid repolarization
Explanation:Phase 0 is caused by the sodium current. Voltage gated sodium channels open leading to the influx of sodium into the cardiac muscle cell. Phase 1 is the rapid transient repolarization phase which is caused by the inactivation of the voltage gated sodium channels and opening of the voltage gated potassium channels along with opening of the slow calcium channels. Phase 2 which is the plateau is caused by opening of the slow calcium channels. Phase 4 is caused by closing of the slow calcium channels and opening of the potassium channels leading to efflux of potassium leading to the establishment of the resting membrane potential.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 166
Incorrect
-
The ability of the SA node cells to allow ionic flow through channels activated in a hyperpolarized state is known as
Your Answer: All of the above
Correct Answer: Pace maker potential
Explanation:Rhythmically discharging cells have a membrane potential that, after each impulse, declines to the firing level. Thus this prepotential or Pacemaker potential triggers the next impulse. The inherent leakiness of the sinus nodal fibers to Na+ and Ca2+ causes their self excitation.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 167
Incorrect
-
Closure of the tricuspid valve is marked by which of the following features of the jugular venous waveform?
Your Answer: a wave
Correct Answer: c wave
Explanation:The jugular venous pressure (JVP) classically has three upward deflections and two downward deflections. The upward deflections are the a (atrial contraction), c (ventricular contraction and resulting bulging of tricuspid into the right atrium during isovolumetric systole) and v = venous filling. The downward deflections of the wave are the x (the atrium relaxes and the tricuspid valve moves downward) and the y descent (filling of ventricle after tricuspid opening).
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 168
Incorrect
-
Question 169
Correct
-
Question 170
Incorrect
-
The amount of a substance taken up by an organ (or whole body) per unit time is equal to the arterial level minus the venous level times the blood flow.” This statement describes:
Your Answer: The cardiac output
Correct Answer: The Fick principle
Explanation:The essence of the Fick principle is that blood flow to an organ can be calculated using a marker substance if the following information is known:- Amount of marker substance taken up by the organ per unit time- Concentration of marker substance in arterial blood supplying the organ- Concentration of marker substance in venous blood leaving the organ
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 171
Incorrect
-
Regarding cardiac output, an increased ejection fraction results from increases in which of the following?
Your Answer: All of the above
Correct Answer: Strength of contraction without increase in muscle fiber length
Explanation:When the strength of contraction increases without an increase in fiber length, the EF increases.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 172
Incorrect
-
Impulse conduction through the AV node is slow and depends on the action potential produced by which of the following.
Your Answer: Sodium diffusion
Correct Answer: Calcium flux
Explanation:The action potentials in the SA and AV nodes are largely due to Ca2+, with no contribution by Na+ influx.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 173
Correct
-
Afferent fibers from the baroreceptors of the great arteries form branches of which cranial nerves?
Your Answer: Glossopharyngeal and vagus nerves
Explanation:The receptors of the carotid sinus are innervated by the carotid sinus nerve, a branch of the glossopharyngeal nerve. The aortic arch receptors located in the arch of the aorta are innervated by the aortic depressor nerve, a branch of the vagus nerve.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 174
Incorrect
-
Question 175
Correct
-
Although variable, branches of which artery most often supply the SA and AV nodes?
Your Answer: Right coronary artery
Explanation:The RCA (right coronary artery) supplies the SA and the AV nodes along with the postero-basal wall of the left ventricle, posterior one third of the inferior vena cava, right ventricle and the posteromedial papillary muscle in the left ventricle.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 176
Incorrect
-
Coronary flow is reduced during
Your Answer: Bradycardia
Correct Answer: Tachycardia
Explanation:Maximum amount of blood flow in the coronary arteries occur during diastole. When the heart rate increases which is also called tachycardia the duration of diastole decreases. Hence the amount of blood flow to the cardiac muscle also decreases.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 177
Incorrect
-
The right border of the heart corresponds to which line on the surface of the chest?
Your Answer: Line drawn from the 4th right costal cartilage to the 5th left intercostal space
Correct Answer: Line drawn from the 3rd right costal cartilage to the 6th right costal cartilage
Explanation:The right border corresponds to a line drawn from the 3rd right costal cartilage to the 6th right costal cartilage; this border is slightly convex to the right.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 178
Incorrect
-
The predominant receptors in the conduction system are?
Your Answer: Both β1 and β2
Correct Answer: Β1
Explanation:The heart is predominately under the control of the parasympathetic system. Nerves from the parasympathetic system activate the B1 receptors on the heart, most specifically on the SA node, AV node and the purkinje system.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 179
Incorrect
-
The most resistant area in the brain to hypoxia is:
Your Answer: Cerebral cortex
Correct Answer: Brain stem
Explanation:The structures in the brainstem are more resistant to hypoxia than the cerebral cortex and the rest of the brain structures.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 180
Incorrect
-
Ventricular depolarization plus ventricular repolarization is shown by the _____ interval
Your Answer: ST
Correct Answer: QT
Explanation:The QT interval represents ventricular depolarization as well as ventricular repolarization.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 181
Correct
-
Which of the following are responsible for the 4th heart sound?
Your Answer: Ventricular hypertrophy
Explanation:The fourth heart sound is not normally audible in a normal adult. It occurs as a consequence of ventricular hypertrophy. It is caused by filling of the ventricle in atrial systole.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 182
Incorrect
-
A 28-year-old patient is intubated and has a central venous catheter inserted after being diagnosed with septic shock. You keep track of her central venous pressure. The normal value for central venous pressure is which of the following?
Your Answer: 0-3 cmH 2 O
Correct Answer: 0-8 cmH 2 O
Explanation:The pressure measured in the right atrium or superior vena cava is known as central venous pressure (CVP). In a spontaneously breathing subject, the usual CVP value is 0-8 cmH2O (0-6 mmHg). At the conclusion of expiration, the CVP should be measured with the patient resting flat. The catheter’s tip should be at the intersection of the superior vena cava and the right atrium. An electronic transducer is installed and zeroed at the level of the right atrium to measure it (usually in the 4th intercostal space in the mid-axillary line). CVP is a good predictor of preload in the right ventricle. Hypovolaemia is indicated by a volume challenge of 250-500 mL crystalloid eliciting an increase in CVP that is not sustained for more than 10 minutes. CVP is influenced by a number of factors, including: Mechanical ventilation (and PEEP) Pulmonary hypertension Pulmonary embolism Heart failure Pleural effusion Decreased cardiac output Cardiac tamponade CVP is reduced by the following factors: Distributive shock Negative pressure ventilation Hypovolaemia Deep inhalation
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 183
Correct
-
Myocardial contractility is improved by:
Your Answer: Caffeine
Explanation:Caffeine and other theophyllines breakdown cAMP and have a positive ionotropic effect on the heart. Drugs like quinidine, procainamide and conditions like hypoxia and hypercapnia decreases the contractility of the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 184
Incorrect
-
The posterior aspect of the interventricular septum is supplied by:
Your Answer: A branch of the anterior interventricular artery
Correct Answer: A branch of the right coronary artery
Explanation:The posterior aspect of the heart is supplied by the posterior interventricular artery which is a branch of the right coronary artery.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 185
Incorrect
-
The ‘c’ wave in JVP corresponds more closely with……
Your Answer: Closure of mitral valve
Correct Answer: Isovolumetric contraction
Explanation:The jugular venous pressure (JVP, sometimes referred to as jugular venous pulse) is the indirectly observed pressure over the venous system via visualization of the internal jugular vein. It can be useful in the differentiation of different forms of heart and lung disease. Classically three upward deflections (peaks) and two downward deflections (troughs) have been described:The upward deflections are the a (atrial contraction), c (ventricular contraction and resulting bulging of tricuspid into the right atrium during isovolumetric systole) and v = venous filling.The downward deflections of the wave are the x (the atrium relaxes and the tricuspid valve moves downward) and the y descent (filling of ventricle after tricuspid opening).
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 186
Incorrect
-
The coronary arteries supply which part of the heart’s subendocardial region exclusively in diastole?
Your Answer: Right atrium
Correct Answer: Left ventricle
Explanation:It is only during diastole that the blood flows to the subendocardial portion of the left ventricle, as the heart muscle relaxes and the coronary arteries regain their patency.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 187
Correct
-
The following are examples of the functions of the vascular endothelium except—
Your Answer: Tumour suppression
Explanation:Vascular endothelium has many important functions including regulation of vascular tone, molecular exchange between blood and tissue compartments, hemostasis and signaling for the immune regulation and inflammation. Depending on specific tissue needs and local stresses, endothelial cells are capable of evoking either antithrombotic or prothrombotic events. A tumor suppression is related to genes, or anti-oncogenes, that regulate a cell during cell division and replication.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 188
Incorrect
-
A 55 year old cardiac patient is comfortable at rest but heavy housework results in fatigue, palpitations or dyspnoea. What New York Heart Association class best describes the severity of their disease?
Your Answer: NYHA Class 0
Correct Answer: NYHA Class II
Explanation:New York Heart Association functional classification:Class I: no limitation is experienced in any activities; there are no symptoms from ordinary activities.Class II: slight, mild limitation of activity; the patient is comfortable at rest or with mild exertion.Class III: marked limitation of any activity; the patient is comfortable only at rest.Class IV: any physical activity brings on discomfort and symptoms occur at rest.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 189
Incorrect
-
Sinus bradycardia may be caused by disease of which of the following:
Your Answer: Left coronary artery
Correct Answer: Right coronary artery
Explanation:Disease of the right coronary artery may cause sinus bradycardia and AV nodal block.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 190
Incorrect
-
Which one of the following have not been shown to improve mortality in patients with chronic heart failure?
Your Answer: Beta-blockers
Correct Answer: Furosemide
Explanation:A number of drugs have been shown to improve mortality in patients with chronic heart failure:• ACE inhibitors (SAVE, SOLVD, CONSENSUS)• spironolactone (RALES)• beta-blockers (CIBIS)• hydralazine with nitrates (VHEFT-1)
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 191
Correct
-
Activation of nitric oxide synthesis by endothelial cells is triggered by:
Your Answer: All of the above
Explanation:Acetylcholine, histamine, bradykinin, vasoactive intestinal peptide (VIP) and shear stress on the endothelial cells causing the release of NO. NO is formed from arginine and causes vasodilatation of the blood vessels.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 192
Incorrect
-
The internodal tract of Bachman:
Your Answer: Its main function is to reduce the amount of conduction to the AV node
Correct Answer: Connects the SA node to the AV node
Explanation:Internodal tract of Bachman connects the SA node to the AV node conducting the electrical impulses generated from the SA node to the AV node and from the AV node to the rest of the electrical complex of the heart.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 193
Incorrect
-
Which heart sounds are matched correctly?
Your Answer: S1 - closure of AV valves
Correct Answer: All of the above
Explanation:In healthy adults, there are two normal heart sounds often described as a lub and a dub (or dup), that occur in sequence with each heartbeat. These are the first heart sound (S1) and second heart sound (S2), produced by the closing of the atrioventricular valves and semilunar valves, respectively. In addition to these normal sounds, a variety of other sounds may be present including heart murmurs, adventitious sounds, and gallop rhythms S3 and S4. S3 is thought to be caused by the oscillation of blood back and forth between the walls of the ventricles initiated by blood rushing in from the atria. The reason the third heart sound does not occur until the middle third of diastole is probably that during the early part of diastole, the ventricles are not filled sufficiently to create enough tension for reverberation. S4 when audible in an adult is called a presystolic gallop or atrial gallop. This gallop is produced by the sound of blood being forced into a stiff or hypertrophic ventricle.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 194
Incorrect
-
Tunica intima is made up of?
Your Answer: Smooth muscle cells
Correct Answer: Endothelial cells
Explanation:Tunica intima is a single cell thick lining of endothelial cells that lines the inside of the blood vessels. It is the inner most layer of the blood vessel.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 195
Incorrect
-
Which one of the following is a risk factor for torsade de pointes?
Your Answer: Hyperkalaemia
Correct Answer: Hypothermia
Explanation:The following is a list of factors associated with an increased tendency toward torsades de pointes:- Hypokalaemia (low blood potassium)- Hypomagnesemia (low blood magnesium)- Hypocalcaemia (low blood calcium)- Bradycardia (slow heartbeat)- Heart failure- Left ventricular hypertrophy- Hypothermia- Subarachnoid haemorrhage- Hypothyroidism
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 196
Incorrect
-
What is the function of the BK channel on the vascular smooth muscle membrane?
Your Answer: Promotes smooth muscle contraction opening the voltage gated Ca2+ channel
Correct Answer: Massive K+ efflux, increasing membrane potential, and shutting off the voltage gated Ca2+ channel
Explanation:In vascular smooth muscles, Ca2+ influx via the voltage gated calcium channels increases the cytosolic calcium, as well as causing release of calcium from the sarcoplasmic reticulum. The high calcium concentration increases the activity of the calcium activated potassium channels. These are known as BK channels. Massive influx of potassium shuts off the voltage gated calcium channels and causes relaxation of the vascular smooth muscle.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 197
Incorrect
-
Why is the sub-endocardial portion of the left ventricle the most common site for ischaemic damage and myocardial infarction?
Your Answer: Easily hypertrophied
Correct Answer: No blood flow occurs during systole
Explanation:The subendocardium receives the least amount of blood from the coronary arteries. During systole the coronary arteries collapse as a result of the pressure due to contraction that is exerted on them. During diastole the heart muscle relaxes and the pressure on the coronary vessels is relieved allowing blood to flow through them to the subendocardium.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 198
Incorrect
-
A sarcomere is the area between
Your Answer: Two adjacent a band
Correct Answer: Two adjacent z lines
Explanation:The area that lies between the two adjacent Z lines is known as a sarcomere and is the contractile unit of the muscle. The line passing in the middle of the myosin filaments is the M line. It also passes through the middle of the sarcomere.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 199
Correct
-
The effects of β1 stimulation include the following
Your Answer: Increased strength of contraction
Explanation:β1 stimulation include the phosphorylation of L type Ca++ channels and phospholamban and increased Ca++ influx from myocytes.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 200
Incorrect
-
With regards to the cardiac cycle which of the following is true
Your Answer: Left ventricular ejection begins before right ventricular ejection
Correct Answer: Right atrial systole occurs before left atrial systole: as below
Explanation:Cardiac cycle: The first event in the cycle is atrial depolarization (a P wave on the surface ECG) follows by RIGHT ATRIAL and then LEFT ATRIAL contraction. Ventricular activation (QRS) follows after a short interval (the PR interval). LEFT VENTRICULAR contraction starts shortly thereafter RIGHT VENTRICULAR contraction begins. At the end, the aortic valve closure is followed by pulmonary valve closure.
-
This question is part of the following fields:
- Cardiovascular
- Physiology
-
SESSION STATS - PERFORMANCE PER SPECIALTY
