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Question 1
Incorrect
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What is the protective hexametric sequence at the ends of chromosomes called?
Your Answer: Histone
Correct Answer: Telomere
Explanation:Telomeres are non coding DNA plus proteins that are found at the end of the linear chromosomes. They maintain the integrity of the chromosomes and prevent their shortening.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 2
Correct
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Question 3
Incorrect
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During which phase are the 2 chromatids pulled apart at the centromere?
Your Answer: Prophase
Correct Answer: Anaphase
Explanation:During the prometaphase the microtubule organizing centre completely develops. The spindle fibers attach to the chromosome and the centriole. It is in the Anaphase however that the spindle fibers contract pulling the sister chromatids apart. Later in the anaphase a cleave furrow beings to forms.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 4
Incorrect
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Consanguinity shows a strong association with which pattern of inheritance?
Your Answer: X linked recessive
Correct Answer: Autosomal recessive
Explanation:Consanguinity involves being from the same kinship as another person. It is a common feature of an autosomal recessive mode of inheritance
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This question is part of the following fields:
- Genetics
- Physiology
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Question 5
Incorrect
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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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 6
Incorrect
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Which of the following cells will degranulate and release histamine when binding to IgE?
Your Answer: Monocytes
Correct Answer: Basophils
Explanation:Basophils have protein receptors on their cell surface that bind IgE, an immunoglobulin involved in microparasite defence and allergy. When activated, basophils degranulate to release histamine, proteoglycans (e.g. heparin and chondroitin), and proteolytic enzymes (e.g. elastase and lysophospholipase).
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This question is part of the following fields:
- Haematology
- Physiology
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Question 7
Incorrect
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What is the function of basic electrical rhythm
Your Answer: Segmentation and mixing
Correct Answer: To coordinate peristalsis and other motor activity
Explanation:The basal or basic electrical rhythm (BER) or electrical control activity (ECA) determines the frequency of the contractions in the gastrointestinal (GI) tract, thus acting to coordinate peristalsis.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 8
Correct
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A 34-year-old woman was diagnosed with multiple sclerosis two years ago. Her symptoms have been steadily deteriorating, with no intervals of remission in sight. Which of the following aspects of nerve conduction is disrupted by multiple sclerosis?
Your Answer: Saltatory conduction
Explanation:Local currents propagate action potentials down the axons of neurons. This local current flow following depolarisation results in the depolarisation of the neighbouring axonal membrane, and when this region approaches the threshold, more action potentials are generated and so forth. Due to the refractory period, portions of the membrane that have recently depolarized will not depolarize again, resulting in the action potential only being able to go in one direction. The square root of axonal diameter determines the velocity of the action potential; the axons with the biggest diameter have the quickest conduction velocities. When a neuron is myelinated, the speed of the action potential rises as well. The myelin sheath is an insulating coating that surrounds certain neural axons. By increasing membrane resistance and decreasing membrane capacitance, the myelin sheath improves conduction. This enables faster electrical signal transmission via a neuron, making them more energy-efficient than non-myelinated neuronal axons. Electrical impulses are quickly transmitted from one node to the next, causing depolarization of the membrane above the threshold and triggering another action potential, which is then transmitted to the next node. An action potential is rapidly conducted down a neuron in this manner. Saltatory conduction is the term for this. Multiple sclerosis is an example of a clinical disorder in which the myelin sheath is affected. It is an immune-mediated disorder in which certain nerve cells in the brain and spinal cord become demyelinated. The ability of some areas of the nervous system to properly transmit action potentials is disrupted by demyelination, resulting in a variety of neurological symptoms and indications.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 9
Correct
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The initial rapid depolarization in the action potential of cardiac muscle cells is due to:
Your Answer: Opening of voltage-gated Na+ channels
Explanation:The initial depolarization of the action potential in a cardiac muscle cell is due to the sodium current generated by opening of the voltage gated sodium channels leading to an influx of sodium ions into the cell and raising the membrane potential towards threshold.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 10
Incorrect
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The tectum as part of the Midbrain contains which structure important in visual reflexes.
Your Answer: Substantia nigra
Correct Answer: Superior colliculus
Explanation:The tectum is a part of the midbrain, specifically, the dorsal part of the midbrain. The tectum consists of the superior and inferior colliculi. The superior colliculus is involved in preliminary visual processing and control of eye movement.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 11
Correct
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During strenuous exercise the following arterial change can take place in a fit athlete:
Your Answer: No change takes place
Explanation:The changes which occur in arterial pH, PO2 and PCO2 values during exercise are usually small. Arterial PO2 often rises slightly because of hyperventilation although it may eventually fall at high work rates. During vigorous exercise, when sufficient oxygen for flux through the Krebs cycle is not available, the increased reliance on glycolysis results in increased accumulation of lactic acid, which initially leads to an increase in PaCO2 . However, this is counteracted by the stimulation of ventilation and as a result PaCO2 is decreased. This provides some respiratory compensation for further lactic acid production and prevents a decline in blood pH, which remains nearly constant during moderate exercise.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 12
Correct
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Which of the following stimulates glucagon release?
Your Answer: Exercise
Explanation:Studies have shown a small increase in glucagon levels during stress tests and exercise. This occurs in response to the reduction of blood glucose levels during physical activity; epinephrine levels are also a stimulus for the release of glucagon during exercise, since it suppresses insulin, which accounts for its stimulatory effects on glucagon. The use of stored fats for energy during exercise also stimulates the release of glucagon.
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This question is part of the following fields:
- Endocrinology
- Physiology
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Question 13
Incorrect
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Question 14
Correct
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What is the result of maltase deficiency in the brush border of the small intestine?
Your Answer: Results in increased passage of maltose in stool
Explanation:Maltase is an enzyme produced from the surface cells of the villi, lining the small intestine and aids in hydrolysing the disaccharide maltose, which splits into two molecules of α-glucose. It is done by breaking the glycosidic bond between the ‘first’ carbon of one glucose and the ‘fourth’ carbon of the other (a 1–4 bond). Hence, a deficiency of enzyme maltase will result in the increased passage of maltose in the stool.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 15
Correct
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All valves are closed in which phase of the cardiac cycle?
Your Answer: Isovolumetric relaxation
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 16
Incorrect
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Which structure forms the major part of the sternocostal surface of the heart?
Your Answer: The aortic arch
Correct Answer: Right ventricle
Explanation:The anterior (sternocostal) surface is formed mainly by the right ventricle.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 17
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
- Physiology
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Question 18
Incorrect
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The coronary sinus drains into the:
Your Answer: Superior vena cava
Correct 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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 19
Incorrect
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The thalamus is a large collection of neuronal groups within the diencephalons which participates in:
Your Answer: Limbic functions only
Correct Answer: Sensory, motor and limbic
Explanation:The thalamus has multiple functions. It is the relay station for every sensory system (except olfactory, regulates the sleep-wake cycle and consciousness and also relays motor information.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 20
Incorrect
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Concerning the functional unit of the liver, which segment is most susceptible to hypoxic damage?
Your Answer: Hepatic triad
Correct Answer: Zone 3
Explanation:From a metabolic perspective, the functional unit is the hepatic acinus (terminal acinus), each of which is centred on the line connecting two portal triads and extends outwards to the two adjacent central veins. The periportal zone I is nearest to the entering vascular supply and receives the most oxygenated blood, making it least sensitive to ischemic injury while making it very susceptible to viral hepatitis. Conversely, the centrilobular zone III has the poorest oxygenation, and will be most affected during a time of ischemia.
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This question is part of the following fields:
- Hepatobiliary
- Physiology
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Question 21
Incorrect
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Which of the following are true when it comes to tumour suppressor genes:
Your Answer: Mutation in the Rb gene leads to retinoblastoma
Correct Answer: All of the options are true
Explanation:All of the above mentioned statements are true regarding tumour suppressor genes. Tumour suppressor genes generally follow the two-hit hypothesis, which implies that both alleles that code for a particular protein must be affected before an effect is manifested.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 22
Incorrect
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Which of the following are responsible for the 4th heart sound?
Your Answer: Closure of the atrio-ventricular valves
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
- Physiology
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Question 23
Incorrect
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What are the diagnostic criteria for an ST segment elevation type of acute myocardial infarction?
Your Answer: 1 mm ST depression in 2 limb leads
Correct 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.)
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 24
Incorrect
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Where in the gastrointestinal tract are Brunner glands?
Your Answer: Jejunum
Correct Answer: Duodenum
Explanation:Brunner’s glands (or duodenal glands) are compound tubular submucosal glands found in that portion of the duodenum which is above the hepatopancreatic sphincter (aka sphincter of Oddi). The main function of these glands is to produce a mucus-rich alkaline secretion (containing bicarbonate) in order to:- protect the duodenum from the acidic content of chyme (which is introduced into the duodenum from the stomach);- provide an alkaline condition for the intestinal enzymes to be active, thus enabling absorption to take place; lubricate the intestinal walls.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 25
Incorrect
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Which of the following cells are attracted to the surface of endothelium by selectins?
Your Answer: Eosinophils
Correct Answer: Neutrophils
Explanation:Selectins are expressed on the surface of the endothelium. P selectins are released from weibel-palade bodies and E selectins are induced by cytokines (TNF and IL-1). They bind to receptors on the neutrophils called saiyl lewis X.
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This question is part of the following fields:
- Immunology
- Physiology
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Question 26
Incorrect
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The only APCs that can activate naive T lymphocytes are:
Your Answer: Macrophages and monocytes
Correct Answer: Dendric cells
Explanation:Only professional antigen-presenting cells (macrophages, B lymphocytes, and dendritic cells) are able to activate a resting helper T-cell when the matching antigen is presented. However, macrophages and B cells can only activate memory T cells whereas dendritic cells can activate both memory and naive T cells, and are the most potent of all the antigen-presenting cells.
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This question is part of the following fields:
- Immunology
- Physiology
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Question 27
Incorrect
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If both the noradrenergic and the cholinergic systems are blocked in the heart, the rate will be approximately:
Your Answer: 50/ 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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 28
Incorrect
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What is the structure of nucleosomes?
Your Answer: Strands of double strand DNA + telomeres
Correct Answer: Strands of double strand DNA + histones
Explanation:DNA is packed and condensed by binding to histone proteins. The double stranded DNA forms a complex with histone proteins which is called a nucleosome. There are 8 histone proteins contained in one core of nucleosome.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 29
Correct
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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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 30
Incorrect
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Question 31
Correct
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The complete oxidation of 1 molecule of glucose to CO2 and H20 produces a total of __ATP.
Your Answer: 38
Explanation:Textbooks often state that 38 ATP molecules can be made per oxidised glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system). However, this maximum yield is never quite reached because of losses due to leaky membranes as well as the cost of moving pyruvate and ADP into the mitochondrial matrix, and current estimates range around 29 to 30 ATP per glucose.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 32
Correct
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Which ONE statement about homeostasis is true?
Your Answer: Negative feedback occurs via receptors, comparators and effectors
Explanation:Homeostasis is the property of a system in which variables are regulated so that internal conditions remain relatively constant and stable. Homeostasis is achieved by a negative feedback mechanism. Negative feedback occurs based upon a set point through receptors, comparators and effectors. The ‘set point’ is a NARROW range of values within which normal function occurs. The two body systems that regulate homeostasis are the Nervous system and the Endocrine system. The smooth muscle of the uterus becomes more active towards the end of pregnancy. This is a POSITIVE feedback.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 33
Incorrect
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The chromosomes that principally encode for proteins or RNA molecules involved in mitochondrial function are found:
Your Answer: In the rough endoplasmic reticulum
Correct Answer: In the mitochondria of the cell
Explanation:DNA is found in chromosomes and in the mitochondria of a cell. The only way for the protein or RNA to be formed is by transcription via the DNA and translation into proteins.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 34
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. Splitting may occur due to pathology.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 35
Incorrect
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The conversion of fructose to fructose 1-phosphate is catalysed by:
Your Answer: Glucose-6-phosphate dehydrogenase
Correct Answer: Fructokinase
Explanation:The first step in the metabolism of fructose is the phosphorylation of fructose to fructose 1-phosphate by fructokinase.
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This question is part of the following fields:
- Metabolism
- Physiology
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Question 36
Incorrect
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Which one of the following leads to decreased prolactin levels?
Your Answer: Oestrogens
Correct Answer: Dopamine
Explanation:Dopamine has an important effect on the regulation of prolactin secretion. Dopamine binds to type-2 dopamine receptors of the lactotroph cells that are functionally linked to membrane channels and G proteins and suppresses the high secretory activity of the pituitary lactotrophs.
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This question is part of the following fields:
- Endocrinology
- Physiology
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Question 37
Correct
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The end product of trehalase action on oligosaccharides is
Your Answer: Two glucose molecules
Explanation:Disaccharides are glycoside hydrolases, enzymes that break down certain types of sugars called disaccharides into simpler sugars called monosaccharides.Examples of disaccharides:Lactase (breaks down lactose into glucose and galactose)Maltase (breaks down maltose into 2 glucoses)Sucrase (breaks down sucrose into glucose and fructose)Trehalase (breaks down trehalose into 2 glucoses)
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 38
Incorrect
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When during the cell cycle does DNA replication occur?
Your Answer: G2 phase
Correct Answer: S phase
Explanation:The S phase is known as the synthesis phase. During this phase DNA will begin to replicated, as well as the synthesis of the centrosomes and associated proteins.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 39
Correct
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Which hormone results in the production of pancreatic juice rich in enzymes but low in volume?
Your Answer: Cholecystokinin
Explanation:Cholecystokinin (CCK) mediates digestion in the small intestine by inhibiting gastric emptying and decreasing gastric acid secretion. It stimulates the acinar cells of the pancreas to release a juice rich in pancreatic digestive enzymes, hence the old name pancreozymin.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 40
Incorrect
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Which of the following statements is not true about mitochondrial chromosomes?
Your Answer: Are mainly inherited from the mother
Correct Answer: Mitochondrial chromosomes play no role in the transmission of disease from generation to generation.
Explanation:All the above mentioned statements are true except that mitochondrial DNA is passed from the mother to the child. If the child inherits the defective mitochondrial gene it will manifest some form of the disease. Commonly inherited diseases related to mitochondrial abnormality are Leber hereditary optic neuropathy and myoclonic epilepsy with ragged red fibers (MERRF).
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This question is part of the following fields:
- Genetics
- Physiology
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Question 41
Incorrect
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What is the role of cyclin and cyklin-dependent kinases in mitosis:
Your Answer: Causes breakdown of the nuclear envelope
Correct Answer: Phosphorylation of proteins that make up pre-replication complexes
Explanation:There are certain regulators of the cell cycles that mediate progression through the cell cycle. These are cyclins and cyklin-dependent kinases (CDKs). They form a complex that phosphorylates protein involved in the cell cycle.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 42
Incorrect
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Platelets are stored in this body organ.
Your Answer: Liver
Correct Answer: Spleen
Explanation:Megakaryocyte and platelet production is regulated by thrombopoietin. Each megakaryocyte produces between 1,000 and 3,000 platelets during its lifetime. An average of 1011 platelets are produced daily in a healthy adult. Reserve platelets are stored in the spleen, and are released when needed by splenic contraction induced by the sympathetic nervous system.
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This question is part of the following fields:
- Haematology
- Physiology
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Question 43
Incorrect
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Which of the atrial pressure changes represents the a-wave of the JVP
Your Answer: Rise in atrial pressure before tricuspid valve opens
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 44
Incorrect
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Which one of the following cells originates from a monocyte and resembles a macrophage?
Your Answer: Astrocyte
Correct Answer: Microglia
Explanation:Microglia act as the macrophages of the central nervous system, and they contribute to innate and adaptive immune responses. Studies have shown that microglial cells recognize monocyte antigens, and there are similarities between them that demonstrate that they originate from these monocytes.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 45
Correct
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Which neuron secretes glutamate as its neurotransmitter?
Your Answer: A delta and C pain fibers
Explanation:A delta and C fibers use glutamate as their primary neurotransmitter where it acts as a fast acting localized neurotransmitter.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 46
Incorrect
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Select the correct statement regarding terminal bronchioles:
Your Answer: Terminal bronchioles form part of the respiratory zone
Correct Answer: Terminal bronchioles form part of the conducting zone
Explanation:Bronchioles divide into even smaller bronchioles, called terminal, which are 0.5mm or less in diameter. Terminal bronchioles in turn divide into smaller respiratory bronchioles which divide into alveolar ducts. Terminal bronchioles mark the end of the conducting division of air flow in the respiratory system while respiratory bronchioles are the beginning of the respiratory division where actual gas exchange takes place. Terminal bronchioles are lined with simple cuboidal epithelium containing club cells. Terminal bronchioles contain a limited number of ciliated cells and no goblet cells. Club cells are non-ciliated, rounded protein secreting cells. Their secretions are a non-stick, proteinaceous compound (surfactant) to maintain the airway in the smallest bronchioles.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 47
Incorrect
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Regarding bronchial innervation which of the following is correct:
Your Answer: Beta 2 receptors mediate bronchoconstriction
Correct Answer: Alpha 1 receptors increase bronchial constriction
Explanation:Stimulation of β2 receptors results in smooth muscle relaxation and bronchodilation. α1 receptors cause smooth muscle contraction in the bronchioles although minor to the β2 effects.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 48
Incorrect
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The ATPase of parietal cells moves:
Your Answer: H+ into the gastric lumen in exchange for a Na+
Correct Answer: H+ into the gastric lumen in exchange for a k+
Explanation:ATPase of the parietal cell is also known as the proton pump, which moves H+ ions into the gastric lumen in exchange for K+ ions into the cell.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 49
Correct
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Cyclic AMP is formed from ATP via which enzyme
Your Answer: Adenylate cyclase
Explanation:Cyclic AMP is synthesized from ATP by adenylate cyclase located on the inner side of the plasma membrane and anchored at various locations in the interior of the cell.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 50
Correct
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Which of the following stimuli increase growth hormone secretion?
Your Answer: Ghrelin
Explanation:Ghrelin is a hormone which serves as an endogenous ligand for the growth hormone secretagogue receptor. It acts on the pituitary and the hypothalamus by affecting the vagus nerve. It acts on the somatotrophs of the anterior pituitary, GHRH-secreting neurons, and on GHIH-secreting neurons in the hypothalamus, causing a time-dependent and pulsatile stimulation over the secretion of growth hormone.
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This question is part of the following fields:
- Endocrinology
- Physiology
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Question 51
Incorrect
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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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 52
Incorrect
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Choose the correct statement about Aminoglycosides and Chloramphenicol
Your Answer: Aminoglycosides work on Ribosome 50 S peptidyl transferase
Correct Answer: Chloramphenicol works on Ribosome 50 S peptidyl transferase
Explanation:Aminoglycoside is a category of traditional Gram-negative antibacterial therapeutic agents that inhibit protein synthesis. Aminoglycoside antibiotics display bactericidal activity against gram-negative aerobes and some anaerobic bacilli where resistance has not yet arisen, but generally not against Gram-positive and anaerobic Gram-negative bacteria.Chloramphenicol is a bacteriostatic by inhibiting protein synthesis. It prevents protein chain elongation by inhibiting the peptidyl transferase activity of the bacterial ribosome. It specifically binds to A2451 and A2452 residues in the 23S rRNA of the 50S ribosomal subunit, preventing peptide bond formation.
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This question is part of the following fields:
- Infectious Diseases
- Physiology
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Question 53
Incorrect
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Low levels of which of the following arterial blood gas parameters stimulate the peripheral chemoreceptors?
Your Answer: Cerebral spinal fluid pH
Correct Answer: Arterial pO 2
Explanation:Chemoreceptors are activated when the chemical composition of their immediate surroundings changes. Peripheral chemoreceptors, together with central chemoreceptors, regulate respiratory functions. They detect changes in arterial blood oxygen levels. Decreased arterial Po2 (partial pressure of oxygen) reflexly stimulates peripheral chemoreceptors. When peripheral chemoreceptors detect changes in arterial blood oxygen, they will trigger cardiorespiratory changes such as an increase in breathing and blood pressure. These reflexes are important for maintaining homeostasis during hypoxemia.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 54
Incorrect
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The enzyme responsible for Telomeres to maintain their length after cell division is called:
Your Answer: Telomere restrictedase
Correct Answer: Telomerase reverse transcriptase
Explanation:Telomeres are non-coding DNA consisting of repetitive nucleotide sequences plus proteins that are found at the end of the linear chromosomes. They maintain the integrity of the chromosomes and prevent their shortening.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 55
Correct
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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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 56
Incorrect
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Under normal conditions (where n represents the number of chromosome pairs), just before mitosis begins, how many chromosomes are contained in the nucleus of each somatic cell:
Your Answer: 2n
Correct Answer: 4n
Explanation:In a normal somatic cell there are 2n chromosome but in a replicating cell just before mitosis the chromosomes duplicate but are still joined via the centrosome. Thus there are 4n chromosomes. After completion of mitosis the number goes back to 2n.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 57
Correct
-
What will the destruction of endoplasmic reticulum stop?
Your Answer: Synthesis of proteins
Explanation:The rough endoplasmic reticulum is the factory for the manufacturing of proteins. It contains ribosomes attached to it and transports proteins that are destined for membranes and secretions. The rough ER is connected to the nuclear envelope and to the cisternae of the Golgi apparatus by vesicles that shuttle between the two compartments.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 58
Incorrect
-
Endolymph in the inner ear is rich in:
Your Answer: Ca
Correct Answer: K
Explanation:Cochlear fluids namely endolymph and perilymph have different compositions. Perilymph is a typical extracellular fluid, with ionic composition comparable to plasma or cerebrospinal fluid. The main cation is sodium. Endolymph is a totally unique extracellular fluid, with an ion composition unlike that which is found anywhere else in the body. The major cation in the endolymph is potassium and there is virtually no sodium.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 59
Correct
-
Peristalsis is an example of:
Your Answer: Enteric nervous system
Explanation:Peristalsis is a type of contraction where radial symmetrical contraction and relaxation of muscles propagates food in a downward wave through the gut. The enteric nervous system is one of the main divisions of the nervous system and consists of a mesh-like system of neurons that controls the function of the gastrointestinal tract. It has an independent reflex activity. The neurons of this system re collected into two types of ganglia: myenteric (or Auerbach’s) and submucosal (or Meissner’s plexuses). Myenteric plexuses are located between the inner and outer layers of the muscularis externa, while submucosal plexuses are located in the submucosa.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 60
Incorrect
-
Question 61
Incorrect
-
In which stage of mitosis are the chromosomes most obvious or prominent?
Your Answer: G1 phase
Correct Answer: Metaphase
Explanation:Prophase begins when the nucleus envelope disintegrates and the chromosomes start to condense. The chromosomes consist of two sister chromatids that are joined at a constriction known as centromere. When the cell reaches the metaphase the chromosomes are completely condensed and ready to align on the equatorial plate.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 62
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 63
Incorrect
-
Which of the following would be a contraindication to thrombolysis?
Your Answer: Menstruation
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
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 64
Incorrect
-
Which ventral (motor) root is responsible for triceps?
Your Answer: C5
Correct Answer: C7
Explanation:Of the nerve fibers that make up the brachial plexus, C7 mainly forms the radial nerve to innervate the triceps muscle, thus innervating the shoulders, elbow, wrist and hand. C7 is responsible for the triceps reflex.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 65
Incorrect
-
The neurotransmitter utilised by the Purkinje cells is:
Your Answer: Glycine
Correct Answer: GABA
Explanation:The cerebellar cortex consist of 3 layers: the molecular layer, the granular cell layer and the Purkinje cell layer. Purkinje cells play a fundamental role in controlling motor movement. They release a neurotransmitter called GABA (gamma-aminobutyric acid) which exerts inhibitory actions thereby reducing transmission of impulses. These inhibitory functions enable purkinje cells to regulate and coordinate motor movements.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 66
Correct
-
When does the heart rate decrease?
Your 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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 67
Incorrect
-
A 24-year-old athlete drinks a 500 ml hypertonic sports drink before an endurance event he participates in. Which of the following effects will this cause?
Your Answer: Cells gain water and swell
Correct Answer: The interstitial fluid becomes more concentrated
Explanation:Osmosis is the passive movement of water across a semipermeable membrane from a region of low solute concentration to a region of higher solute concentration. When hypertonic fluid is ingested: The plasma becomes CONCENTRATED. The cells lose water and shrink The intracellular fluid becomes more concentrated. Water and ions move freely from the plasma into the interstitial fluid and the interstitial fluid becomes more concentrated. The increased osmotic potential draws water out of the cells.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 68
Correct
-
Which of the following proteins are NOT synthesized in the liver?
Your Answer: Steroid
Explanation:Human steroidogenesis occurs in a number of locations:- Corticosteroids are produced in the adrenal cortex.- Oestrogen and progesterone are made primarily in the ovary and the placenta during pregnancy, and testosterone in the testes.- Testosterone is also converted to oestrogen to regulate the supply of each in females and males.- Some neurons and glia in the central nervous system (CNS) express the enzymes required for the local synthesis of pregnant neurosteroids, de novo or from peripheral sources.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
-
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Question 69
Incorrect
-
Which of these vitamins is not found in plants?
Your Answer: Folate
Correct Answer: Vitamin B12
Explanation:No fungi, plants, nor animals (including humans) are capable of producing vitamin B12. Only bacteria and archaea have the enzymes needed for its synthesis. Proved food sources of B12 are animal products (meat, fish, dairy products).
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This question is part of the following fields:
- Haematology
- Physiology
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Question 70
Incorrect
-
Which law describes the rate of diffusion in a solution?
Your Answer: Ohm’s law
Correct Answer: Fick’s law
Explanation:Fick’s law describes the rate of diffusion in a solution. Fick’s law states that: Jx = -D A (ΔC / Δx) Where: Jx = The amount of substance transferred per unit time D = Diffusion coefficient of that particular substance A = Surface area over which diffusion occurs ΔC = Concentration difference across the membrane Δx = Distance over which diffusion occurs The negative sign reflects movement down the concentration gradient
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 71
Incorrect
-
Transport of Ca2+ into the reticulum to initiate cardiac muscle relaxation in via:
Your Answer: Calmodulin
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).
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 72
Correct
-
Which of the following initiates migrating motor complex
Your Answer: Motilin
Explanation:Migrating motor complexes (MMC) are thought to be partially regulated by motilin, which is initiated in the stomach as a response to vagal stimulation, and does not directly depend on extrinsic nerves.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
-
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Question 73
Incorrect
-
Which of the following is a form of synaptic plasticity?
Your Answer: Neurogenesis
Correct Answer: Working memory
Explanation:Synaptic plasticity is an important neurochemical foundation of working memory and generation of memory. Synaptic plasticity is the ability of synapses to strengthen or weaken over time in response to increases or decreases in their activity.
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This question is part of the following fields:
- Neurology
- Physiology
-
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Question 74
Correct
-
Which of the following is first to rise following myocardial infarction?
Your Answer: Myoglobin
Explanation:Myoglobin, is a sensitive indicator of muscle injury and is first to rise following MI within two hours but is nonspecific.Troponin and CK-MB both begin to rise approximately three hours after MI. The cardiac troponins T and I which are released within 4–6 hours of an attack of MI and remain elevated for up to 2 weeks, have nearly complete tissue specificity and are now the preferred markers for assessing myocardial damage.Lactate dehydrogenase (LDH) begins to rise approximately 12 hours after MI.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 75
Incorrect
-
Which of the following statements is true of the beta- lactams:
Your Answer: Acts by directly disrupting bacterial cell walls
Correct Answer: Co-amoxiclav is more likely to cause obstructive jaundice than amoxicillin
Explanation:β-lactam antibiotics are a class of broad-spectrum antibiotics, consisting of all antibiotic agents that contain a β-lactam ring in their molecular structures. This includes penicillin derivatives (penams), cephalosporins (cephems), monobactams, and carbapenems. Most β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics. Bacteria often develop resistance to β-lactam antibiotics by synthesizing a β-lactamase, an enzyme that attacks the β-lactam ring. To overcome this resistance, β-lactam antibiotics are often given with β-lactamase inhibitors such as clavulanic acid. Immunologically mediated adverse reactions to any β-lactam antibiotic may occur in up to 10% of patients receiving that agent (a small fraction of which are truly IgE-mediated allergic reactions). Rarely, cholestatic jaundice has been associated with Co-amoxiclav (amoxicillin/clavulanic acid). The reaction may occur up to several weeks after treatment has stopped, and usually takes weeks to resolve. It is more frequent in men, older people, and those who have taken long courses of treatment; the estimated overall incidence is one in 100,000 exposures.
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This question is part of the following fields:
- Infectious Diseases
- Physiology
-
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Question 76
Incorrect
-
Which of these structures is the smallest and deepest component of muscle connective tissue?
Your Answer: Sarcolemma
Correct Answer: Endomysium
Explanation:There are three types of muscle: Skeletal muscle Cardiac muscle Smooth muscle Individual muscle is enveloped in a layer of dense irregular connective tissue called the epimysium. The epimysium protects the muscles from friction against bones and other muscles. Skeletal muscle is composed of muscle fibres, referred to as myofibers which is ensheathed by a wispy layer of areolar connective tissue called the endomysium. The endomysium is the smallest and deepest component of muscle connective tissue. Myofibers grouped together in bundles form fascicles, or fasciculi. These are surrounded by a type of connective tissue called the perimysium. Beneath the endomysium lies the sarcolemma, an elastic sheath with infoldings that invaginate the interior of the myofibers, particularly at the motor endplate of the neuromuscular junction.
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This question is part of the following fields:
- Cell Biology
- Physiology
-
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Question 77
Incorrect
-
Question 78
Correct
-
The cells that secrete pepsinogen and gastric lipase are found in which part of the stomach?
Your Answer: Body and antrum
Explanation:Stomach can be divided in to different regions. Cardia, fundus, body, antrum and pylorus from proximal end to distal end respectively. Cells that secret the inactive form of pepsin or pepsinogen are chief cells and are abundant in the body and the antral region of the stomach.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
-
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Question 79
Incorrect
-
Which of the following statements with regards to regulation of pulmonary blood flow is correct:
Your Answer: Oxygen deficiency indirectly causes vasoconstriction
Correct Answer: Decreased blood flow to a region causes constriction of bronchi that area
Explanation:Oxygen deficiency or hypoxia has a direct effect on pulmonary vessels and results in vasoconstriction. Increased carbon dioxide levels causes pH levels to fall and results in pulmonary vasoconstriction. Decreased blood flow to a pulmonary region causes bronchoconstriction in that area to allow for flow of blood to an area where ventilation is high. Exercise increases demand of oxygen and causes increased pulmonary artery pressure.
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This question is part of the following fields:
- Physiology
- Respiratory
-
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Question 80
Incorrect
-
Mean intra pleural pressure at rest with inspiration can reach:
Your Answer: -10 mmHg
Correct Answer: -6 mmHg
Explanation:It is a negative pressure as it is lower than the atmospheric pressure. It can start from -2.5 and reach around -6 mmHg
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This question is part of the following fields:
- Physiology
- Respiratory
-
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Question 81
Incorrect
-
The process whereby DNA fragments are separated by size and charge is called:
Your Answer: Northern blotting
Correct Answer: Gel electrophoresis
Explanation:Fragments of DNA of varying length can be separated on the basis of their charge and their size by a process called gel electrophoresis. Because DNA contains negatively charged phosphate groups, it will migrate in an electric field toward the positive electrode. Shorter chains migrate more rapidly through the pores of the gel, and thus separation depends on length. DNA bands in the gel can be visualized by various techniques including staining with dyes and autoradiography.
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This question is part of the following fields:
- Genetics
- Physiology
-
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Question 82
Incorrect
-
Which neurotransmitter is released from the postganglionic fibers in the sympathetic division?
Your Answer: Acetylcholine
Correct Answer: Noradrenalin
Explanation:Noradrenalin Is the neurotransmitter that is released from the postganglionic fibers of the sympathetic division. It is stored in granules at the sympathetic knobs. It Is a methyl derivative.
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This question is part of the following fields:
- Neurology
- Physiology
-
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Question 83
Incorrect
-
In the body what are fatty acids broken down to?
Your Answer: Carnitine
Correct Answer: Acetyl Co A
Explanation:Fatty acids are broken down into acetyl Co A. The acetyl-CoA produced by beta oxidation enters the citric acid cycle in the mitochondrion by combining with oxaloacetate to form citrate.
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This question is part of the following fields:
- Cell Biology
- Physiology
-
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Question 84
Correct
-
Which of the following may be a feature of primary hyperaldosteronism?
Your Answer: Muscular weakness
Explanation:Primary hyperaldosteronism or Conn’s syndrome is characterised by hypertension which may cause poor vision or headaches. Occasionally there may be muscular weakness, muscle spasms, tingling sensations, or excessive urination. Complications include cardiovascular disease such as stroke, myocardial infarction, kidney failure, and abnormal heart rhythms.
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This question is part of the following fields:
- Endocrinology
- Physiology
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Question 85
Correct
-
Select a factor which stimulates glucagon secretion.
Your Answer: Protein meal
Explanation:Several studies have shown that glucagon levels are increased in individuals with a high protein diet. It is still debated, however, whether this type of diet affects insulin levels as well.
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This question is part of the following fields:
- Endocrinology
- Physiology
-
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Question 86
Incorrect
-
Which statement is incorrect regarding nociceptor C fibers…
Your Answer: They conduct at low rates (0.5-2 m/s)
Correct Answer: They are thinly myelinated
Explanation:Group C nerve fibers are unmyelinated and have a small diameter, which means they conduct impulses at a low velocity. They carry sensory information and nociception.
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This question is part of the following fields:
- Neurology
- Physiology
-
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Question 87
Incorrect
-
Which of the following best describe Clostridium infection?
Your Answer: Gram negative bacilli
Correct Answer: Anaerobe
Explanation:Clostridium is a genus of Gram-positive bacteria, which includes several significant human pathogens, including the causative agent of botulism and an important cause of diarrhoea, Clostridium difficile. They are obligate anaerobes capable of producing endospores. The normal, reproducing cells of Clostridium, called the vegetative form, are rod-shaped, which gives them their name, from the Greek κλωστήρ or spindle.
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This question is part of the following fields:
- Infectious Diseases
- Physiology
-
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Question 88
Incorrect
-
Which of the following does not lower ventricular rate in atrial fibrillation?
Your Answer: Acetylcholine
Correct Answer: Adrenaline
Explanation:Adrenaline is a sympathetic neurotransmitter which increases the heart rate. During atrial fibrillation the atria is contracting at more than 200 beats/min. Acetylcholine is a parasympathetic neurotransmitter decreasing the heart rate. Digital also depresses the conduction at the AV conduction. Vagal discharge and occulocardiac reflux decrease the heart rate and convert the tachycardia into normal sinus rhythm.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 89
Incorrect
-
Cross-bridges between actin and myosin filaments contain:
Your Answer: Tropomyosin
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 90
Correct
-
Where does protein digestion begin?
Your Answer: Stomach
Explanation:Digestion typically begins in the stomach when pepsinogen is converted to pepsin by the action of hydrochloric acid, and continued by trypsin and chymotrypsin in the small intestine.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
-
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Question 91
Incorrect
-
What percentage of the cardiac output is delivered to the brain?
Your Answer: 80%
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%.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
-
Question 92
Incorrect
-
The rate limiting pump in the HCL secretion is the?
Your Answer: Chloride/bicarbonate exchanger
Correct Answer: Hydrogen potassium ATPase
Explanation:The rate limiting pump in HCl secretion is the H+/K+ ATPase pump.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
-
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Question 93
Incorrect
-
In the basal ganglia, the Lentiform nucleus is formed by which two nuclei?
Your Answer: Globus pallidus and subthalamus
Correct Answer: Putamen and Globus pallidus
Explanation:The Basal Ganglia are composed of the following structures: Caudate, putamen, Globus pallidus, subthalamic nucleus and substantia nigra. The lentiform nucleus comprises of the putamen and the Globus pallidus.
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This question is part of the following fields:
- Neurology
- Physiology
-
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Question 94
Incorrect
-
Regarding taste threshold and intensity discrimination:
Your Answer: 10% change in concentration of substance tasted is necessary before an intensity difference can be detected
Correct Answer: 30% change in concentration of substance tasted is necessary before an intensity difference can be detected
Explanation:The ability of humans to differentiate differences in intensity of taste is poor. A 30% change in the concentration of the substance being tasted is required before an intensity difference is perceived.
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This question is part of the following fields:
- Neurology
- Physiology
-
-
Question 95
Incorrect
-
Which mechanism of action does Trimethoprim use?
Your Answer: Inhibit DNA gyrase
Correct Answer: Inhibit Folic Acid metabolism
Explanation:Trimethoprim binds to dihydrofolate reductase and inhibits the reduction of dihydrofolic acid (DHF) to tetrahydrofolic acid (THF). THF is an essential precursor in the thymidine synthesis pathway and interference with this pathway inhibits bacterial DNA synthesis.
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This question is part of the following fields:
- Infectious Diseases
- Physiology
-
-
Question 96
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 97
Correct
-
The thalamic nuclei that project over wide regions of the neocortex are:
Your Answer: Specific relay nuclei
Explanation:The thalamus is considered the relay station for sensory and motor stimuli. There are three basic types of thalamic nuclei: relay nuclei, association nuclei and non-specific nuclei. Relay nuclei receive very well defined inputs and project this signal to functionally distinct areas of the cerebral cortex. These include the nuclei that relay primary sensations and also the nuclei involved in feedback of cerebellar signals and basal gangliar output.
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This question is part of the following fields:
- Neurology
- Physiology
-
-
Question 98
Incorrect
-
Translation usually begins at which codon?
Your Answer: AGU
Correct Answer: AUG
Explanation:The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and the most common start codon is AUG.
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This question is part of the following fields:
- Metabolism
- Physiology
-
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Question 99
Incorrect
-
What is the enzyme that is involved in the formation of citrulline?
Your Answer: Glycogen synthase
Correct Answer: Ornithine transcarbamoylase
Explanation:Carbamoyl phosphate is converted to citrulline by ornithine transcarbamoylase.
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This question is part of the following fields:
- Cell Biology
- Physiology
-
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Question 100
Correct
-
Which protein in the HIV genome is responsible for binding to the host CD4 cells?
Your Answer: gp120
Explanation:HIV can infect a variety of immune cells such as CD4+ T cells, macrophages, and microglial cells. HIV-1 entry to macrophages and CD4+ T cells is mediated through interaction of the virion envelope glycoproteins (gp120) with the CD4 molecule on the target cells and also with chemokine coreceptors.
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This question is part of the following fields:
- Infectious Diseases
- Physiology
-
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Question 101
Incorrect
-
Which of the following is a product of D cells
Your Answer: HCL
Correct Answer: Somatostatin
Explanation:Somatostatin is secreted by D cells, HCL and intrinsic factor secreted by parietal cells. Trefoil peptides are secreted by mucus secreting goblet cells and gastrin releasing peptide (grp) by post-ganglionic fibers of the vagus nerve (which innervate the G cells of the stomach).
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This question is part of the following fields:
- Gastrointestinal
- Physiology
-
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Question 102
Incorrect
-
The approximate incidence of deep venous thrombosis (DVT) in the general population each year is:
Your Answer: 50 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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 103
Incorrect
-
Regarding cardiac muscle contractility, the afterload refers to:
Your Answer: The amount of blood pumped out of the heart per beat
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 104
Incorrect
-
The oesophagus is lined by
Your Answer: Simple columnar epithelium
Correct Answer: Stratified squamous epithelium
Explanation:The wall of the oesophagus from the lumen outwards consists of mucosa, submucosa (connective tissue), layers of muscle fibers between layers of fibrous tissue, and an outer layer of connective tissue. The mucosa is a stratified squamous epithelium of around three layers of squamous cells, which contrasts to the single layer of columnar cells of the stomach. The transition between these two types of epithelium is visible as a zig-zag line. Most of the muscle is smooth muscle although striated muscle predominates in its upper two thirds.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
-
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Question 105
Incorrect
-
What is the average life span of neutrophils?
Your Answer: 4 months
Correct Answer: 24 hours
Explanation:The average lifespan of inactivated human neutrophils in the circulation has been reported by different approaches to be between 5 and 90 hours.
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This question is part of the following fields:
- Haematology
- Physiology
-
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Question 106
Incorrect
-
Where are the cell bodies to the preganglionic neurons located?
Your Answer: Forebrain
Correct Answer: Midbrain
Explanation:The cell bodies of the preganglionic neurons are located in the lateral grey column of the spinal cord and in the motor nuclei of the 3rd, 7th, 9th and 10th cranial nerves. These cranial nerves take origin from the midbrain.
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This question is part of the following fields:
- Neurology
- Physiology
-
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Question 107
Correct
-
The telomerase is capable of adding several more repeats of telomeres at which end of the guanosine rich region.
Your Answer: 3rd end
Explanation:Telomerase is a reverse transcriptase that uses the RNA template to synthesize DNA in the 5th-3rd direction resulting in extension of the 3rd end and then translocates it to the newly synthesized end. The GT rich strand is thus elongated.
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This question is part of the following fields:
- Genetics
- Physiology
-
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Question 108
Incorrect
-
When oxygen supply is restored, lactate formed during anaerobic metabolism is converted back to?
Your Answer: Glucose-6-phosphate
Correct Answer: Pyruvate
Explanation:During intense exercise, when the rate of demand for energy is high, glucose is broken down and oxidized to pyruvate, and lactate is then produced from the pyruvate faster than the body can process it, causing lactate concentrations to rise. The resulting lactate can be used in two ways:1. Oxidation back to pyruvate by well-oxygenated muscle cells, heart cells, and brain cells. Pyruvate is then directly used to fuel the Krebs cycle2. Conversion to glucose via gluconeogenesis in the liver and release back into circulation.
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This question is part of the following fields:
- Metabolism
- Physiology
-
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Question 109
Correct
-
Which of the following predominate in the renal medulla?
Your Answer: Epinephrine secreting cells
Explanation:Chromaffin cells, also known as pheochromocytes, are cells located in the adrenal medulla which specialize in the synthesis, storage, and secretion of catecholamines: 80% epinephrine and 20% norepinephrine is released into the bloodstream. For this reason, they are considered to be neuroendocrine cells.
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This question is part of the following fields:
- Endocrinology
- Physiology
-
-
Question 110
Incorrect
-
Sequence of events in formation of speech are:
Your Answer: Broca’s area---motor cortex---insula---arcuate fasciculus---Wernicke's area---speech
Correct Answer: Wernicke’s area---arcuate fasciculus---broca’s area---insula---motor cortex---speech
Explanation:Wernicke’s area is located in the categorical hemisphere or left hemisphere in about 95% of right handed individuals and 60% of left handed individuals. It is involved in the comprehension or understanding of written and spoken language. In contrast Broca’s area is involved in production of language. Firstly, the language is accessed in the Wernicke’s area and these words are sent via the arcuate fasciculus to the Broca’s area, where instructions for articulation is generated. This is then sent from Broca’s are to the motor cortex for the articulation.
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This question is part of the following fields:
- Neurology
- Physiology
-
-
Question 111
Incorrect
-
The process where by DNA fragments are separated by size and charge is called:
Your Answer: Blotting
Correct Answer: Gel electrophoresis
Explanation:Fragments of DNA of varying length can be separated on the basis of their charge and their size by a process called gel electrophoresis. Because DNA contains negatively charged phosphate groups, it will migrate in an electric field toward the positive electrode. Shorter chains migrate more rapidly through the pores of the gel, and thus separation depends on length. DNA bands in the gel can be visualized by various techniques including staining with dyes and autoradiography.
-
This question is part of the following fields:
- Genetics
- Physiology
-
-
Question 112
Incorrect
-
Regarding blood supply to the heart;
Your Answer: Coronary arteries arise immediately above the cusps of the pulmonary valve
Correct Answer: Coronary arteries fill as the heart relaxes
Explanation:The heart muscles acts like the skeletal muscle in the fact that it also compress the vessels during contraction. As the pressure in the ventricle is slightly greater than in the aorta the coronary vessels collapse during systole. Blood flows through them during the diastole phase of contraction.
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This question is part of the following fields:
- Cardiovascular
- Physiology
-
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Question 113
Incorrect
-
The small opening in the cochlea through which the upper scala vestibuli and lower scala tympani communicates is called the:
Your Answer: Oval window
Correct Answer: Helicotrema
Explanation:The helicotrema is the part of cochlear labyrinth where the scala tympani and the scala vestibuli meet.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 114
Incorrect
-
Gastrin activates all of the following cells except:
Your Answer: Chief cells
Correct Answer: Mucus neck cells
Explanation:The G cell is a type of cell in the stomach and duodenum that secretes gastrin. It works in conjunction with gastric chief cells and parietal cells. G cells are found deep within the pyloric glands of the stomach antrum, and occasionally in the pancreas and duodenum. Gastrin-releasing peptide, as well as the presence of amino acids in the stomach, stimulates the release of gastrin from the G cells. Gastrin stimulates enterochromaffin-like cells to secrete histamine. Gastrin also targets parietal cells by increasing the amount of histamine and the direct stimulation by gastrin, causing the parietal cells to increase HCl secretion in the stomach.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 115
Incorrect
-
When 2 nucleotide chains of DNA bind together, thymine is bound to:
Your Answer: Amino acids
Correct Answer: Adenine
Explanation:As a general rule in the structure of DNA, thymine always binds to adenine with two hydrogen bonds, cytosine always binds to guanine with three hydrogen bonds and vice versa. However In the structure of RNA the only difference is that adenine binds to uracil instead of thymine. But thymine will always bind to adenine.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 116
Correct
-
Which one of these equations best defines lung compliance?
Your Answer: Change in volume / change in pressure
Explanation:Lung compliance is defined as change in volume per unit change in distending pressure. Lung compliance is calculated using the equation: Lung compliance = ΔV / ΔP Where: ΔV is the change in volume ΔP is the change in pleural pressure. Static compliance is lung compliance in periods without gas flow, and is calculated using the equation: Static compliance = VT / Pplat − PEEP Where: VT = tidal volume Pplat = plateau pressure PEEP = positive end-expiratory pressure
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 117
Incorrect
-
What proportion of salivary secretions is contributed by the submandibular glands?
Your Answer: 90%
Correct Answer: 70%
Explanation:The submandibular glands provide the bulk of salivary secretions contributing close to 70%. The sublingual glands provide 5% and the remainder from the parotid.
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This question is part of the following fields:
- Fluids & Electrolytes
- Physiology
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Question 118
Incorrect
-
Free radicals are best defined by which of the following statements.
Your Answer: Atoms or molecules with electrical charge
Correct Answer: Atoms or molecules with unpaired electrons
Explanation:Free radicals form when one of weak bond between electrons is broken and an uneven number of electrons remain. This means the electron is unpaired, making it chemically reactive and attempt to steal an electron from a neighbouring molecule to stabilize itself.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 119
Incorrect
-
At rest, proton pumps are sequestered within the parietal cell in a series of membrane compartments known as:
Your Answer: Microvilli
Correct Answer: Tubulovesicles
Explanation:The gastric H, K-ATPase pump, which pumps gastric acid (HCl), in the resting state is found in cytoplasmic tubular membranes. In the stimulated state this pump moves from the tubulovesicles to the apical membrane.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 120
Incorrect
-
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: Pulmonary trunk
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
- Physiology
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Question 121
Incorrect
-
Why does arterial blood pressure drop during pregnancy?
Your Answer: Oestrogen relaxes vascular smooth muscle
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 122
Correct
-
Sympathetic supply to the stomach is derived from
Your Answer: T5-T9 spinal segments via the coeliac ganglion
Explanation:Parasympathetic innervation to the stomach is from the vagus nerve and the sympathetic innervation is from the T5-T9 spinal segments via the coeliac ganglion through the greater splanchnic nerve.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 123
Correct
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Question 124
Incorrect
-
What is the effect of catecholamines (i.e. increased heart rate) on the pressure volume loop?
Your Answer: Stroke volume is enormous
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 125
Incorrect
-
What is the main function of vitamin E?
Your Answer: It is a cofactor in carbohydrate metabolism
Correct Answer: It is an antioxidant
Explanation:Vitamin E has many biological functions, the antioxidant function being the best known. Other functions include enzymatic activities, gene expression, and neurological function(s).
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This question is part of the following fields:
- Haematology
- Physiology
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Question 126
Incorrect
-
A 58-year-old patient presents with sputum production and worsening exertional breathlessness. A spirometry is done and his results leads to a diagnosis of obstructive lung disease with mild airflow obstruction. What FEV1 value would correspond with mild airflow obstruction according to the NICE guidelines?
Your Answer: FEV 1 30-49%
Correct Answer: FEV 1 >80%
Explanation:Airflow obstruction according to the latest NICE guidelines, is defined as: Mild airflow obstruction = an FEV 1 of >80% in the presence of symptoms Moderate airflow obstruction = FEV 1 of 50-79% Severe airflow obstruction = FEV 1 of 30-49% Very severe airflow obstruction = FEV1<30%.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 127
Correct
-
Direct conduction from the atrium to the ventricles is prevented by:
Your 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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 128
Incorrect
-
Cardiac myocytes contract by excitation-contraction coupling, very much like skeletal myocytes. On the other hand, calcium-induced calcium release (CICR) is a mechanism that is unique to Cardiac myocytes. The influx of calcium ions (Ca 2+) into the cell causes a 'calcium spark,' which causes more ions to be released into the cytoplasm. In CICR, which membrane protein in the sarcoplasmic reticulum is involved?
Your Answer: Voltage-gated potassium channel
Correct Answer: Ryanodine receptor
Explanation:Cardiac myocytes contract by excitation-contraction coupling, just like skeletal myocytes. Heart myocytes, on the other hand, utilise a calcium-induced calcium release mechanism that is unique to cardiac muscle (CICR). The influx of calcium ions (Ca2+) into the cell causes a ‘calcium spark,’ which causes more ions to be released into the cytoplasm. An influx of sodium ions induces an initial depolarisation, much as it does in skeletal muscle; however, in cardiac muscle, the inflow of Ca2+ sustains the depolarisation, allowing it to remain longer. Due to potassium ion (K+) inflow, CICR causes a plateau phase in which the cells remain depolarized for a short time before repolarizing. Skeletal muscle, on the other hand, repolarizes almost instantly. The release of Ca2+ from the sarcoplasmic reticulum is required for calcium-induced calcium release (CICR). This is mostly accomplished by ryanodine receptors (RyR) on the sarcoplasmic reticulum membrane; Ca2+ binds to RyR, causing additional Ca2+ to be released.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 129
Incorrect
-
You've been asked to give a discussion to a group of medical students about skeletal muscle physiology and its use in clinical medicine. They pose a series of difficult questions to you. Which of the following definitions for the A-band of the sarcomere is correct?
Your Answer: A disc in the middle of the H-zone formed of cross-connecting elements of the cytoskeleton
Correct Answer: A band that contains the entire length of a single thick filament (myosin)
Explanation:Myofibrils, which are around 1 m in diameter, make up each myofiber. The cytoplasm separates them and arranges them in a parallel pattern along the cell’s long axis. These myofibrils are made up of actin and myosin filaments that are repeated in sarcomeres, which are the myofiber’s basic functional units. Myofilaments are the filaments that make up myofibrils, and they’re made mostly of proteins. Myofilaments are divided into three categories: Myosin filaments are thick filaments made up mostly of the protein myosin. Actin filaments are thin filaments made up mostly of the protein actin. Elastic filaments are mostly made up of the protein titin. The sarcomere is a Z-line segment that connects two adjacent Z-lines. The I-bands are thin filament zones that run from either side of the Z-lines to the thick filament’s beginning. Between the I-bands is the A-band, which spans the length of a single thick filament. The H-zone is a zone of thick filaments that is not overlaid by thin filaments in the sarcomere’s centre. The H-zone keeps the myosin filaments in place by surrounding them with six actin filaments each. The M-band (or M-line) is a disc of cross-connecting cytoskeleton elements in the centre of the H-zone. The thick filament is primarily made up of myosin. The thin filament is primarily made up of actin. Actin, tropomyosin, and troponin are found in a 7:1:1 ratio in thin filaments.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 130
Incorrect
-
The pressure in the sinusoids is normally:
Your Answer: Higher than hepatic artery pressure
Correct Answer: Lower than portal venous pressure
Explanation:The direction of transport of nutrients in the portal vein occurs from the portal vein to the hepatic sinusoids. Thus, he pressure of sinusoids should be lower than the pressure of he portal vein.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 131
Incorrect
-
During anaerobic glycolysis, the net production of ATP is:
Your Answer: 18
Correct Answer: 2
Explanation:Anaerobic glycolysis is the transformation of glucose to lactate when limited amounts of oxygen (O2) are available. Anaerobic glycolysis is only an effective means of energy production during short, intense exercise, providing energy for a period ranging from 10 seconds to 2 minutes. It produces 2 ATP molecules per glucose molecule.
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This question is part of the following fields:
- Metabolism
- Physiology
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Question 132
Incorrect
-
“Ploidy” is a term used to refer to the number of chromosomes in cells. Cancer cells are commonly:
Your Answer: Biploidy
Correct Answer: Aneuploidy
Explanation:Cancer cells most commonly undergo disordered cell growth and cell division. This results in an additional number of chromosomes called aneuploidy. This is a characteristic of cancer cells along with variation in differentiation of the cells.
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This question is part of the following fields:
- Genetics
- Physiology
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Question 133
Incorrect
-
Which of the following is matched correctly with regard to stem cells of the bone marrow?
Your Answer: None of the above
Correct Answer: Hemopoietic stem cells - basophils
Explanation:Hematopoietic stem cells (HSCs) or hemocytoblasts are the stem cells that give rise to all the other blood cells through the process of haematopoiesis. They give rise to both the myeloid and lymphoid lineages of blood cells. (Myeloid cells include monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, dendritic cells, and megakaryocytes or platelets. Lymphoid cells include T cells, B cells, and natural killer cells.)
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This question is part of the following fields:
- Haematology
- Physiology
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Question 134
Incorrect
-
Bile contains:
Your Answer: Gastric juices, biliverdin, urea
Correct Answer: Bile acids, phosphatidylcholine, cholesterol
Explanation:The main components of bile include bile acids or bile salts, phospholipids; mainly phosphatidylcholine, cholesterol, bilirubin, inorganic salts; potassium, sodium and bicarbonate.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 135
Incorrect
-
The following are Gram-negative cocci:
Your Answer: Clostridium
Correct Answer: Neisseria
Explanation:Gram-negative cocci include the four types that cause a sexually transmitted disease (Neisseria gonorrhoeae), a meningitis (Neisseria meningitidis), and respiratory symptoms (Moraxella catarrhalis, Haemophilus influenzae).
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This question is part of the following fields:
- Infectious Diseases
- Physiology
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Question 136
Incorrect
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Question 137
Incorrect
-
Functions of the glossopharyngeal nerve include the following except:
Your Answer: Motor supply to pharyngeal muscles of swallowing
Correct Answer: Proprioceptive input from muscles of the tongue and larynx
Explanation:The glossopharyngeal nerve is a mixed nerve consisting of both sensory and motor fibers. It has several branches and five distinct general functions:Branchial motor- Special visceral efferent- supplies the Stylopharyngeus muscle and superior constrictor muscle.Visceral motor- general visceral efferent- provides parasympathetic innervation of the parotid gland.Visceral sensory- general visceral afferent- carries visceral sensory information from the carotid sinus and carotid body.General sensory- general somatic afferent- provides general sensory information from the inner surface of the tympanic membrane, upper pharynx and posterior one third of the tongue.Visceral afferent- special visceral afferent- provides taste sensation from the posterior one third of the tongue including the circumvallate papillae.
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This question is part of the following fields:
- Neurology
- Physiology
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Question 138
Incorrect
-
The febrile response to PGE2 will be impaired with the knockout of which one of the following prostaglandin receptors?
Your Answer: Ep5
Correct Answer: Ep3
Explanation:Prostaglandin EP3 receptor is a receptor for prostaglandin E2. Fever occurs as a result of the action of prostaglandin E2 and requires EP3 receptors in the preoptic area. Therefore, if there is an absence of EP3 receptors, fever caused by prostaglandin E2 will not occur.
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This question is part of the following fields:
- Endocrinology
- Physiology
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Question 139
Correct
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Question 140
Incorrect
-
Microtubule disassembly:
Your Answer: Does not occur simultaneously with microtubule assembly.
Correct Answer: Occurs at the positive and negative end
Explanation:Dynamic instability refers to the coexistence of assembly and disassembly at the ends of a microtubule. The microtubule can dynamically switch between growing and shrinking phases in this region. Although both assembly and disassembly occur at both ends they occur preferentially at the (+) end.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 141
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 142
Incorrect
-
Intermediate filaments achieve cell to cell contact via:
Your Answer: Tight junctions
Correct Answer: Hemidesmosomes
Explanation:At the plasma membrane, some keratins interact with desmosomes (cell-cell adhesion) and hemidesmosomes (cell-matrix adhesion) via adapter proteins.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 143
Correct
-
Which one of the following is most likely to be seen in a patient with multiple endocrine neoplasia (MEN) type I?
Your Answer: Insulinoma
Explanation:Multiple endocrine neoplasia type 1 (MEN-1 syndrome) or Wermer’s syndrome is part of a group of disorders, the multiple endocrine neoplasias, that affect the endocrine system through development of neoplastic lesions in the ‘three P’s’:Parathyroid (>90%): hyperparathyroidism due to parathyroid hyperplasiaPituitary (15-42%)Pancreas (60-70%, e.g. insulinoma, gastrinoma)
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This question is part of the following fields:
- Endocrinology
- Physiology
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Question 144
Incorrect
-
Which of the following biochemical profiles is seen in a normal 65 year old female? (in comparison to a normal 24 yr. old female)
Your Answer: Decreased FSH, LH; decreased oestrogen, progesterone
Correct Answer: Increased FSH, LH; decreased oestrogen, progesterone
Explanation:During menopause, a woman’s number of ovarian follicles becomes depleted; as a result, oestrogen and progesterone levels drop, and LH and FSH levels increase. One of the criteria to diagnose menopause is the absence of menstrual period for a year, along with a serum FSH level increased to 30 mIU/ml or higher. LH also rises with the onset of menopause.
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This question is part of the following fields:
- Endocrinology
- Physiology
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Question 145
Incorrect
-
Coronary arteries fill up during
Your Answer: Ventricular ejection
Correct 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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 146
Correct
-
The celiac trunk consists of which arteries?
Your 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
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 147
Incorrect
-
In cardiac muscle, which of the following is directly responsible for the release of Ca2+ stored in the sarcoplasmic reticulum (calcium-induced calcium release)?
Your Answer: Dihydropyridine receptors (DHPR)
Correct Answer: Ryanodine receptor (RyR)
Explanation:Ryanodine receptor (RyR) is a ligand-gated Ca2+ channel with Ca2+ as its natural ligand. In skeletal muscle, Ca2+ entry from ECF by this route is not required for Ca2+ release. Instead, the DHPR that serves as the voltage sensor unlocks release of Ca2+ from the nearby SR via physical interaction with the RyR. The release is amplified through ca-induced ca release. However, in cardiac muscle, it is the influx of extracellular Ca2+ through the voltage-sensitive DHPR in the T system that triggers ca-induced ca release trough the RyR at the SR.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 148
Incorrect
-
Describe the location of the SA node:
Your Answer: Base of the right atrium
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.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 149
Incorrect
-
How does an action potential in the motor end plate rapidly spread to the central portions of the muscle cells?
Your Answer: Z-lines
Correct Answer: Transverse tubules
Explanation:When the concentration of intracellular Ca2+rises, muscle contraction occurs. The pathway of an action potential is down tube-shaped invaginations of the sarcolemma called T-tubules (transverse tubules). These penetrate throughout the muscle fibre and lie adjacent to the terminal cisternae of the sarcoplasmic reticulum. The voltage changes in the T-tubules result in the opening of sarcoplasmic reticulum Ca2+channels and there is there is release of stored Ca2+into the sarcoplasm. Thus muscle contraction occurs via excitation-contraction coupling (ECC) mechanism.
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This question is part of the following fields:
- Cell Biology
- Physiology
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Question 150
Incorrect
-
During which phase of the cardiac cycle does most of the ventricular filling occur?
Your Answer:
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
- Physiology
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SESSION STATS - PERFORMANCE PER SPECIALTY
