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Question 1
Incorrect
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All of the following statement about the microcirculation are correct except:
Your Answer: Plasma oncotic pressure tends to draw fluid intravascularly.
Correct Answer: Over the capillary bed, there is a net absorption of fluid.
Explanation:The hydrostatic pressure along the length of the capillary is usually greater than plasma oncotic pressure. As a result, there is a small net filtration of fluid from the capillary into the interstitial space. The regulation of blood flow into the microcirculation is via the vasoconstriction of small arterioles, which is activated by the sympathetic nervous system through numerous nerve endings in their walls. Unlike proteins, most ions and small molecules diffuse easily across capillary walls and thus the crystalloid osmotic pressure they exert is roughly the same on either side of the capillary wall. Because the plasma colloid osmotic pressure is higher than interstitial colloid osmotic, fluid is drawn intravascularly. A reduction of hydrostatic capillary pressure and transient increase in absorption of fluid is a result of arteriolar constriction.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 2
Correct
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What is the main mechanism of action of flecainide:
Your Answer: Blocks Na+ channels
Explanation:Flecainide inhibits the transmembrane influx of extracellular Na+ ions via fast channels on cardiac tissues resulting in a decrease in rate of depolarisation of the action potential, prolonging the PR and QRS intervals. At high concentrations, it exerts inhibitory effects on slow Ca2+ channels, accompanied by moderate negative inotropic effect.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 3
Incorrect
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Which of the following is the primary indication for loop diuretics?
Your Answer: Hypertension
Correct Answer: Acute pulmonary oedema
Explanation:Loop diuretics have long been the cornerstone of pulmonary oedema treatment, with furosemide being the most commonly used of these drugs. Premedication with drugs that decrease preload (e.g., nitro-glycerine [NTG]) and afterload (e.g., angiotensin-converting enzyme [ACE] inhibitors) before the administration of loop diuretics can prevent adverse hemodynamic changes.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 4
Correct
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Noradrenaline exhibits its positive inotropic effect by which of the following mechanisms:
Your Answer: Binds to beta1-receptors and causes increased Ca2+ entry via L-type channels during the action potential
Explanation:Noradrenaline (the sympathetic neurotransmitter) is a positive inotrope; it binds to β1-adrenoceptors on the membrane and causes increased Ca2+entry via L-type channels during the AP and thus increases Ca2+release from the SR. Noradrenaline also increases Ca2+sequestration into the SR and thus more Ca2+is available for the next contraction. Cardiac glycosides (e.g. digoxin) slow the removal of Ca2+from the cell by inhibiting the membrane Na+pump which generates the Na+gradient required for driving the export of Ca2+; consequently the removal of Ca2+from the myocyte is slowed and more Ca2+is available for the next contraction. Acidosis is negatively inotropic, largely because H+competes for Ca2+binding sites.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 5
Incorrect
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If the ejection fraction increases, there will be a decrease in:
Your Answer: Mean arterial pressure
Correct Answer: End-systolic volume
Explanation:An increase in ejection fraction means that a higher fraction of the end-diastolic volume is ejected in the stroke volume (e.g. because of the administration of a positive inotropic agent). When this situation occurs, the volume remaining in the ventricle after systole, the end-systolic volume, will be reduced. Cardiac output, stroke volume, and mean arterial pressure will be increased.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 6
Correct
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Question 7
Correct
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A 72 year old man is brought to ED by ambulance with sudden onset chest pain, palpitations and shortness of breath. His HR is 160 bpm and BP 90/65. ECG demonstrates new-onset fast atrial fibrillation. Which of the following is the first-line treatment option in this case:
Your Answer: Synchronised DC cardioversion
Explanation:All patients with adverse features suggesting life-threatening haemodynamic instability (shock, syncope, heart failure, myocardial ischaemia) caused by new onset atrial fibrillation should undergo emergency electrical cardioversion with synchronised DC shock without delaying to achieve anticoagulation.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 8
Correct
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Myocardial contractility is best correlated with the intracellular concentration of:
Your Answer: Ca2+
Explanation:Contractility of myocardial cells depends on the intracellular [Ca2+], which is regulated by Ca2+entry across the cell membrane during the plateau of the action potential and by Ca2+uptake into and release from the sarcoplasmic reticulum (SR).
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 9
Correct
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On which of the following is preload primarily dependent?
Your Answer: End-diastolic volume
Explanation:Preload refers to the initial stretching of the cardiac myocytes before contraction. It is therefore related to muscle sarcomere length. The sarcomere length cannot be determined in the intact heart, and so, other indices of preload are used, like ventricular end-diastolic volume or pressure. The end-diastolic pressure and volume of the ventricles increase when venous return to the heart is increased, and this stretches the sarcomeres, which increase their preload.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 10
Correct
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What is the primary mode of action of Enoxaparin?
Your Answer: Inhibits factor Xa
Explanation:Heparin acts as an anticoagulant by enhancing the inhibition rate of clotting proteases by antithrombin III impairing normal haemostasis and inhibition of factor Xa. Low molecular weight heparins have a small effect on the activated partial thromboplastin time and strongly inhibit factor Xa. Enoxaparin is derived from porcine heparin that undergoes benzylation followed by alkaline depolymerization.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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SESSION STATS - PERFORMANCE PER SPECIALTY
