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Question 1
Correct
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The T-tubular system in cardiac muscle is:
Your 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 2
Correct
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Vasodilatation of coronary arteries is caused by:
Your Answer: Hypoxia
Explanation:The heart is highly metabolically active and boasts the highest oxygen consumption by mass of any organ. This demand for oxygen is met by the coronary circulation, which is responsible for delivering blood to the myocardium and represents approximately 5% of cardiac output. Vasodilation may be due to the local effect of hypoxia on coronary vessels, or local metabolic vasodilation, or the activation of β-adrenoceptors or some combination of these mechanisms.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 3
Incorrect
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Catecholamines…
Your Answer: Are both positive ionotropic and negative chronotropic
Correct Answer: Activate adenylyl cyclase
Explanation:Norepinephrine and epinephrine activate or deactivate adenylyl cyclase resulting in a decrease or an increase in the production of cAMP.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 4
Incorrect
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Question 5
Incorrect
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Which of the following is NOT associated with the development of aortic regurgitation?
Your Answer: Bechet's disease
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
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 6
Correct
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The amount of a substance taken up by an organ (or whole body) per unit time is = (the arterial level - the venous level) * the blood flow. This statement describes?
Your 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
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 7
Correct
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Where is the carotid sinus located?
Your Answer: After the bifurcation of the carotid artery, on the internal carotid
Explanation:The carotid sinus is a small dilation in the internal carotid artery just above its bifurcation into the external and internal carotid branch. Baroreceptors are present at this dilation.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 8
Correct
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Regarding cardiac contractility, catecholamines exert their inotropic effect via:
Your Answer: Î’1-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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 9
Correct
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Blood flow to the subendocardial portions of the left ventricular muscle occurs mainly during:
Your 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 10
Incorrect
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Nitric oxide triggers vascular smooth muscle contraction through activation of which enzyme?
Your Answer: Adenylate cyclase
Correct Answer: Guanylyl cyclase
Explanation:Impaired production or excess catabolism of NO impairs this endothelium-dependent vasodilator function and may contribute to excessive vasoconstriction under various pathological situations.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 11
Correct
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Which statement about the 2nd heart sound is true?
Your Answer: It is caused by closure of the aortic and pulmonary valves.
Explanation:The second heart sound is produced due to closure of the aortic and pulmonary valves. It is a high pitched dub sound.
Normally the aortic closure sound (A2) occurs prior to the pulmonic closure sound (P2), and the interval between the two (splitting) widens on inspiration and narrows on expiration. With quiet respiration, A2 will normally precede P2 by 0.02 to 0.08 second (mean, 0.03 to 0.04 sec) with inspiration. In younger subjects inspiratory splitting averages 0.04 to 0.05 second during quiet respiration. With expiration, A2 and P2 may be superimposed and are rarely split as much as 0.04 second. If the second sound is split by greater than 0.04 second on expiration, it is usually abnormal. Therefore, the presence of audible splitting during expiration (i.e., the ability to hear two distinct sounds during expiration) is of greater significance at the bedside in identifying underlying cardiac pathology than is the absolute inspiratory increase in the A2–P2 interval.
The respiratory variation of the second heart sound can be categorized as follows: (1) normal (physiologic) splitting; (2) persistent (audible expiratory) splitting, with normal respiratory variation; (3) persistent splitting without respiratory variation (fixed splitting); and (4) reversed (paradoxical) splitting.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 12
Correct
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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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 13
Correct
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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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 14
Correct
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The Wiebel-Palade body found in the endothelial cells is responsible for the production and release of which factor?
Your Answer: Von Willebrand factor
Explanation:Weibel-Palade bodies are the storage granules of endothelial cells, the cells that form the inner lining of the blood vessels and heart. They store and release two principal molecules, von Willebrand factor and P-selectin, and thus play a dual role in haemostasis and inflammation.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 15
Incorrect
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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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 16
Correct
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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: 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 17
Incorrect
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Myocyte action potentials – Choose the false statement:
Your Answer: Myocardial fibers have a resting membrane potential of about -90mv
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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 18
Correct
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Calcium is mobilized from the sarcoplasmic reticulum through:
Your Answer: Ryanodine receptor (RyR2) calcium release channels
Explanation:During the plateau phase of the action potential, calcium from the extracellular fluid enters through the L type of calcium channels. This entry triggers the release of more calcium from the sarcoplasmic reticulum via the ryanodine receptors. As a result intracellular calcium increases binding to troponin C resulting in contraction.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 19
Correct
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Question 20
Incorrect
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Which of the following structures of the cardiac conduction system is located in the right posterior portion of the interatrial septum?
Your Answer: Purkinje system
Correct Answer: AV node
Explanation:AV node is located at the right posterior portion of the interatrial septum.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 21
Incorrect
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Which of the following are responsible for the 4th heart sound?
Your Answer: Rapid ventricular filling
Correct 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 22
Correct
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Concerning coronary arteries, what is the net effect of B2 stimulation on the heart (e.g. Running athlete)?
Your 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 23
Incorrect
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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: Aortic arch
Correct 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 24
Incorrect
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Which of the following pairs are correct concerning arteriolar tone?
Your Answer: Neural control: vasoconstriction activated by sympathetic nerves
Correct Answer: Hormonal control: catecholamines affect the adrenergic receptors of the vascular smooth muscle
Explanation:Catecholamines released from the adrenal medulla act on the noradrenergic receptors of the vascular smooth muscles. In the skeletal muscles and liver it causes vasodilation whilst it causes vasoconstriction in the rest of the blood vessels of the body.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 25
Correct
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Question 26
Correct
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What is the function of the BK channel on the vascular smooth muscle membrane?
Your Answer: Massive K+ efflux, increasing membrane potential, and shutting off the voltage gated Ca2+ channel
Explanation:BK channels, also known as large-conductance calcium-activated potassium channels, play a critical role in regulating vascular smooth muscle tone. When BK channels open, they allow a large efflux of potassium ions (K+) out of the cell. This efflux of K+ causes the membrane potential to become more negative (hyperpolarization), which in turn leads to the closure of voltage-gated calcium channels. The closure of these calcium channels reduces the influx of calcium ions (Ca2+) into the smooth muscle cells, resulting in decreased intracellular calcium levels and subsequent relaxation of the smooth muscle.
Thus, BK channels promote smooth muscle relaxation by hyperpolarizing the membrane and reducing the activity of voltage-gated Ca2+ channels.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 27
Incorrect
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During which phase of the cardiac cycle does most of the ventricular filling occur?
Your Answer: Atrial systole
Correct 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 28
Correct
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Question 29
Correct
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Why is the sub-endocardial portion of the left ventricle the most common site for ischaemic damage and myocardial infarction?
Your 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 30
Correct
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Excitation-contraction coupling in cardiac muscle involves all of the following except:
Your 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.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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SESSION STATS - PERFORMANCE PER SPECIALTY
