Cardiovascular System Quiz Questions Flashcards
Which ONE of the following is responsible for the rapid depolarization phase of an action potential within the pacemaker cells? A. An increase in PCa2+ B. An increase in PK+ C. A decrease in PK+ D. An increase in PNa+ E. A decrease in PNa+
Answer: An increase in PCa2+.
An increase in PCa2+ allows Ca to flow into the cell causing the rapid depolarization phase of an action potential within the pacemaker cells.
Which ONE of the following statements regarding blood vessels is INCORRECT?
A. Veins function as volume reservoirs due to their high compliance.
B. The pressure in venules would be less than the pressure in large veins.
C. Capillaries are the vessel type that have the greatest total surface area.
D. The elastic nature of the walls of arteries allows them to act as a pressure reservoir.
E. The contractile activity of smooth muscle cells within arterioles is primarily involved in the control of organ blood flow.
Answer: The pressure in venules would be less than the pressure in large veins.
The pressure in the large veins is lower than the pressure in the venules.
A reflex increase in heart rate may be caused by:
A. a decrease in arterial blood pressure.
B. an increase in right atrial pressure.
C. a decrease in peripheral resistance.
D. an increase in venous return.
E. all of the above.
Answer: all of the above.
Increased right atrial pressure is usually a result of increased venous return and would activate low-pressure baroreceptors or volume receptors in the atrial wall, which would increase heart rate. Decreased arterial blood pressure (also the result of a decrease in peripheral resistance) would activate high-pressure baroreceptors in the aortic arch and carotid bodies, also causing a reflex increase in heart rate.
The greatest proportion of blood volume is present within which ONE of the following vessel types? A. Systemic capillaries B. Pulmonary blood vessels C. Systemic veins and venules D. Heart E. Systemic arteries and arterioles
Answer: Systemic veins and venules
The venules and veins contain about 60% of the total blood volume.
The major mechanism controlling the diameter of arteries in the skin is:
A. sympathetic nerve activity
B. extracellular CO2 concentration
C. myogenic
D. extracellular K+ concentration
E. accumulation of metabolic waste products
Answer: sympathetic nerve activity
Sympathetic nerve activity is the most important controller of blood flow in the skin.
Closure of the aortic valve is associated with all of the following except:
A. rapid filling of the left ventricle.
B. dicrotic notch on the aortic pressure wave.
C. relaxation of the ventricle.
D. the second heart sound.
E. T-wave of the ECG.
Answer: rapid filling of the left ventricle.
Closure of the aortic valve is not associated with rapid filling of the left ventricle. Rapid filling of the left ventricle occurs some time after the aortic valve has closed.
According to Fick’s law, which ONE of the following would NOT be a factor in diffusion of a substance across the capillary wall?
A. The plasma concentration of the substance
B. Hydrostatic (blood) pressure in the capillary
C. The total surface area of the capillary wall
D. The molecular weight of the substance
E. The concentration of the substance in the interstitial fluid
Answer: Hydrostatic (blood) pressure in the capillary
Hydrostatic pressure in capillaries is important in controlling filtration or absorption of water from or into capillaries, but has no role in determining diffusion of solutes as defined by Fick’s Law (J=-PS(Co-Ci)).
In cardiac muscle, the action potential in the ventricles:
A. has an unstable resting membrane potential.
B. is shorter than the action potential of a pacemaker cell.
C. has a resting membrane potential of about -60mV.
D. is due to an increase in chloride permeability.
E. relies on an increase in calcium permeability.
Answer: relies on an increase in calcium permeability.
An increase in calcium permeability is responsible for the plateau phase of this action potential.
Which ONE of the following statements about an action potential generated from a non-pacemaker cardiac cell is INCORRECT?
A. Repolarisation occurs as a result of inactivation of K+ channels.
B. The plateau phase of the action potential is associated with a prolonged increase in Ca2+permeability.
C. The refractory period in ventricular muscle corresponds approximately to the plateau phase of the action potential.
D. The resting membrane potential depends to a great extent on the permeability of the cell membrane to K+.
E. Depolarisation is initiated by rapid entry of Na+.
Answer: Repolarisation occurs as a result of inactivation of K+ channels.
This is the incorrect statement. Repolarisation occurs as a result of activation (not inactivation) of K+ channels.
Pre-load is equivalent to A. Peak ejection pressure B. Stroke volume C. Ventricular end-diastolic volume (EDV) D. Right atrial pressure E. Ventricular end-systolic volume (ESV)
Answer: Ventricular end-diastolic volume (EDV)
Pre-load is the degree to which the ventricular muscle fibres are stretched prior to contraction, and the degree of stretch is determined by the amount of blood in the ventricle at the end of the filling phase, which is the end of diastole, the end-diastolic volume.
Unlike blood vessels, the lymphatic system:
A. removes damaged erythrocytes from the circulation.
B. has a role in controlling blood pressure.
C. reabsorbs protein and foreign particles from the interstitial fluid.
D. forms a filtrate which eventually becomes urine.
E. can generate local vasoactive substances.
Answer: reabsorbs protein and foreign particles from the interstitial fluid.
Compared to sinoatrial cells, ventricular contractile cells will have:
A. A more negative resting membrane potential
B. A smaller amplitude action potential
C. An action potential with a shorter duration
D. A slower conduction velocity
E. A slower depolarisation during the action potential
Answer: A more negative resting membrane potential
Ventricular cells have a much more negative resting membrane potential than sinoatrial cells.
Which ONE choice indicates three events that occur at about the same time during the cardiac cycle?
A. A-V valve closure, second heart sound, ventricular diastole.
B. semilunar valve closure, second heart sound, ventricular systole.
C. A-V valve closure, first heart sound, ventricular systole.
D. A-V valve closure, first heart sound, ventricular diastole.
E. semilunar valve closure, first heart sound, ventricular diastole.
Answer: A-V valve closure, first heart sound, ventricular systole.
At the beginning of ventricular systole, the AV valve closes generating the first heart sound.
Which ONE of the following parameters, when increased, will cause an increase in cardiac stroke volume? A. peripheral resistance B. blood pressure C. afterload D. end-systolic volume (ESV) E. end-diastolic volume (EDV)
Answer: end-diastolic volume (EDV)
Stroke volume = end-diastolic volume - end systolic volume. So if end-diastolic volume is increased, stroke volume would increase.
The decrease in blood pressure is greatest across \_\_\_\_\_\_ because this is where \_\_\_\_\_\_ is highest. A. capillaries, cross-sectional area B. capillaries, resistance C. veins, cross-sectional area D. arterioles, resistance E. aorta, cross-sectional area
Answer: arterioles, resistance
Resistance = Pressure Gradient / Flow. Resistance to flow is highest in arterioles, and this is where the greatest decrease in blood pressure occurs (from 80 to about 30 mmHg).
Cardiac stroke volume may be defined as
A. end-systolic volume (ESV) minus end-diastolic volume (EDV)
B. afterload minus pre-load
C. end-diastolic volume (EDV) minus end-systolic volume (ESV)
D. peak ejection pressure minus diastolic pressure
E. pre-load minus afterload
Answer: end-diastolic volume (EDV) minus end-systolic volume (ESV)
Which ONE of the following would NOT result in an increase in the movement of fluid out of capillaries?
A. An increase in blood pressure within the capillary.
B. A decrease in colloid osmotic pressure of the plasma.
C. A decrease in the osmotic pressure of the interstitial fluid
D. A decrease in interstitial fluid pressure
E. None of the above
Answer: A decrease in the osmotic pressure of the interstitial fluid
Using Starling’s equation,
Jv = k[(Pc + πif)-(Pif + πp)], a decrease in the osmotic pressure of the interstitial fluid (πif), would decrease outward fluid movement from the plasma.
If systemic blood pressure falls, the carotid baroreceptors would cause heart rate to ______ and peripheral ________.
A. Stay the same, vasoconstriction B. Increase, vasodilation C. Decrease, vasoconstriction D. Decrease, vasodilation E. Increase, vasoconstriction
Answer: Increase, vasoconstriction
If blood pressure falls, baroreceptors would act to increase blood pressure. Increased heart rate would increase cardiac output (CO) and peripheral vasoconstriction would increase total peripheral resistance (TPR). As blood pressure = CO x TPR, these actions would increase blood pressure.
Stimulation of the heart by sympathetic nerves
A. causes tachycardia
B. results in inhibition the baroreceptor reflex
C. has no effect on cardiac function
D. results in activation of the baroreceptor reflex
E. causes bradycardia
Answer: causes tachycardia
Sympathetic nerves innervating the heart increase heart rate.
According to Poiseuille’s equation, blood flow in a vessel would be reduced by half when:
A. blood viscosity is halved.
B. vessel length is doubled.
C. vessel diameter is halved.
D. the pressure gradient along the length of vessel is doubled.
E. blood flow velocity is doubled.
Answer: vessel length is doubled.
Key mechanisms in combating orthostatic or postural hypotension include:
A. the baroreceptor reflex.
B. reduced distensibility of leg veins compared to thoracic veins.
C. muscle pumps.
D. all of the above.
E. none of the above.
Answer: all of the above.
Which ONE of the following statements regarding blood vessels is INCORRECT?
A. Veins are sometimes called capacitance vessels.
B. Arterioles contain smooth muscle in their walls.
C. Arteries contain large amounts of elastic tissue in their walls.
D. Arterioles are sometimes called resistance vessels.
E. Capillaries contain smooth muscle in their walls.
Answer: Capillaries contain smooth muscle in their walls
This is the incorrect statement. Capillary walls are made up of a single layer of endothelial cells and a basement membrane and do not contain muscle.
Which ONE of the following is INCORRECT regarding the mechanism by which the substance moves across the wall of a capillary?
A. Net water transport depends upon net (hydraulic) filtration pressure.
B. Oxygen permeation is more than 1000 times faster than glucose permeation.
C. Urea diffuses across the wall down its concentration gradient.
D. Glucose is carried across the wall by plasma filtration.
E. Respiratory gases permeate rapidly, because they are lipid soluble.
Answer: Glucose is carried across the wall by plasma filtration.
This is the incorrect statement. Transcapillary glucose transport is by diffusion down a concentration gradient.
The function of the papillary muscles and chordae tendinae is to:
A. Keep the AV valves from bulging into the atria during ventricular contraction.
B. Increase backflow into the ventricles during diastole.
C. Hold open the semilunar valves during systole.
D. Hold the AV valves open during diastole.
E. Keep the AV valves from bulging into the aorta and pulmonary arteries during systole.
Answer: Keep the AV valves from bulging into the atria during ventricular contraction.
The flaps of the AV valves are anchored to the papillary muscles of the ventricles by chordae tendinae. The papillary muscles pull the valves inwards towards the ventricles by exerting tension on the chordae tendinae and thus prevent or minimise the amount of bulging into the atria during systole.
