During the rapid ejection phase of the cardiac cycle, which ONE of the following statements is INCORRECT?
The ventricular volume is at its lowest
The ventricular volume does drop during this phase but actually reaches its lowest point during the reduced ejection phase.
A patient absorbs 300ml/min of oxygen. The oxygen content of blood taken from the femoral artery = 18ml/100ml and blood taken from the pulmonary artery has an oxygen content of 13ml/100ml. If the patient has a heart rate of 60 beats/min, the patient’s stroke volume is:
The volume reflex, in which heart rate and renal blood flow are increased following an increase in blood volume, is mediated primarily by:
atrial and vena cava baroreceptors
Atrial and vena cava baroreceptors are sensitive to stretch of the wall of these vascular compartments,
which is mainly caused by changes in blood volume, given the pressure in these compartments is usually very low (<3 mmHg).
Unlike blood vessels, the lymphatic system:
reabsorbs protein and foreign particles from the interstitial fluid.
The firing rate of aortic baroreceptors is increased by
increased blood pressure.
Myogenic mechanisms involved in autoregulation of blood flow are activated by:
altered intra-luminal blood pressure.
Myogenic mechanisms result from the interaction between blood pressure and the resulting degree of
stretch or tension in the vessel wall, and are independent of all other factors listed.
The repolarisation of pacemaker cells is due in part to:
an increase in the permeability of potassium.
The repolarisation of pacemaker cells is due in part to an increase in the permeability of potassium and
also in part due to a decrease in permeability of Ca .
In cardiac muscle, the action potential in the ventricles:
relies on an increase in calcium permeability.
An increase in calcium permeability is responsible for the plateau phase of this action potential.
Compared to sinoatrial cells, ventricular contractile cells will have:
A more negative resting membrane potential
Ventricular cells have a much more negative resting membrane potential than sinoatrial cells.
According to the Starling Equation, which ONE of the following would NOT be a factor in the net filtration pressure controlling the movement of water across the capillary wall?
The number and size of the pores in the capillary wall.
The number and size of the pores in the capillary wall would not be a factor in the net filtration pressure controlling the movement of water across the capillary
wall. It may alter the volumes that move, but not the net pressure.
Which ONE of the following is INCORRECT regarding the mechanism by which the substance moves across the wall of a capillary?
Glucose is carried across the wall by plasma filtration.
Transcapillary glucose transport is by diffusion down a concentration gradient.
The major mechanism controlling the diameter of arteries in the skin is:
sympathetic nerve activity
Sympathetic nerve activity is the most important controller of blood flow in the skin.
The decrease in blood pressure is greatest across ______ because this is where ______is highest.
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).
Closure of the aortic valve is associated with all of the following except:
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.
An increase in myocardial contractility will result in:
decreased end-systolic volume and increased stroke volume.
An increase in myocardial contractility will mean a greater proportion of the heart’s content of blood will be ejected during systole. So end-systolic volume will decrease
and stroke volume will increase.
Cardiac stroke volume may be defined as
end-diastolic volume (EDV) minus end-systolic volume (ESV)
is increased by adrenaline
Adrenaline increases the force of cardiac myocyte contraction by acting on beta-adrenergic receptors on the
Which ONE of the following organs/tissues receives the greatest increase in systemic blood flow during exercise?
Which ONE of the following statements regarding blood vessels is INCORRECT?
Capillaries contain smooth muscle in their walls.
Capillary walls are made up of a single layer of endothelial cells and a basement membrane and do not contain muscle.
A reflex increase in heart rate may be caused by:
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.
Stimulation of the heart by parasympathetic nerves
Parasympathetic nerves represent the effector-arm of the baroreceptor reflex, and slow the heart rate (bradycardia).
According to Fick’s law, which ONE of the following would NOT be a factor in diffusion of a substance across the capillary wall?
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)).
During which phase of the cardiac cycle are all four heart valves open?
all four heart valves are normally never open simultaneously
The major mechanism controlling coronary artery diameter is:
accumulation of metabolic waste products.
The key mechanism increasing coronary blood flow is metabolic hyperemia, i.e. the dilation of coronary resistance arteries by accumulated metabolic waste products.
The major mechanism(s) controlling the diameter of arteries in the skeletal muscle is
all of the above
extracellular K concentration, extracellular CO concentration, myogenic mechanisms, accumulation of metabolic waste products
Which ONE of the following is responsible for the rapid depolarization phase of an action potential within the pacemaker cells?
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
Which ONE of the following is true of the ventricular filling phase of the cardiac cycle?
Ventricular pressure is less than aortic pressure
Ventricular pressure is low and aortic pressure is much higher.
Blood that leaves the right ventricle and later enters the left ventricle must have passed through which of the following valves?
Pulmonary and bicuspid/mitral valves.
According to Poiseuille’s equation, blood flow in a vessel would be reduced by half when:
vessel length is doubled.
Which ONE choice indicates three events that occur at about the same time during the cardiac cycle?
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 would NOT result in an increase in the movement of fluid out of capillaries?
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.
According to Poiseuille’s equation, reducing a blood vessel’s diameter by 20% would reduce blood flow in the vessel by (approximately):
According to Poiseuille’s Law flow is proportional to the radius to the power of 4 (r ) of the conducting vessel. A 20% reduction in the diameter of a vessel would reduce flow by 0.8 , which is 0.4096 - or a 60% reduction from the starting value.
What is occurring during ventricular ejection?
The AV valves are closed and the semilunar valves are open as blood is leaving the ventricles.
Which ONE of the following statements is INCORRECT? Increased sympathetic nervous system activity to the sinoatrial node:
decreases the slope of the spontaneous depolarisation of these action potentials
Increased SNS activity would increase the slope of spontaneous depolarisation allowing threshold to be reached more quickly.
The function of the papillary muscles and chordae tendinae is to:
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.
Which ONE of the following statements about an action potential generated from a non-pacemaker cardiac cell is INCORRECT?
Repolarisation occurs as a result of inactivation of K channels
Repolarisation occurs as a result of activation (not inactivation) of K channels.
Stimulation of the heart by sympathetic nerves
Sympathetic nerves innervating the heart increase heart rate.
If systemic blood pressure falls, the carotid baroreceptors would cause heart rate to ______ and peripheral ________.
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.
Key mechanisms in combating orthostatic or postural hypotension include:
all of the above
the baroreceptor reflex., muscle pumps., reduced distensibility of leg veins compared to thoracic veins.
Starling’s Law of the Heart means that when ventricular pre-load is increased, stroke volume will
Starling’s Law dictates that an increase in pre-load, will
result in the stimulated ventricular muscle contracting with increased force. Thus more blood will be ejected during contraction, resulting in an increased stroke
Pre-load is equivalent to
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.
Which ONE of the following statements about the conduction system of the heart is INCORRECT?
Electrical events can spread directly between atria and ventricles through gap junctions.
Electrical impulses cannot spread directly between atria and ventricles. They must pass through the AV node. The atria are insulated from the ventricles by the atrioventricular groove.
Which ONE of the following parameters, when increased, will cause an increase in cardiac stroke volume?
end-diastolic volume (EDV)
Stroke volume = end-diastolic volume - end systolic volume. So if end-diastolic volume is increased, stroke volume would increase.
Which ONE of the following statements about an action potential generated from a sinus nodal fibre is INCORRECT?
The unstable baseline can be partly attributable to a progressive decrease in Ca permeability
The unstable baseline can be partly attributable to a small progressive increase (not decrease) in Ca
permeability due to the opening of T (transient) channels.
The greatest proportion of blood volume is present within which ONE of the following vessel types?
Systemic veins and venules
The venules and veins contain about 60% of the total blood volume.
Blood flow velocity is slowest in ______ because this is where ______ is greatest.
capillaries, cross-sectional area
As the circulatory elements are arranged in parallel, the capillaries present the greatest total crosssectional
area within the entire circulatory system, therefore this is where blood flow velocity is the slowest.
Which ONE of the following statements regarding blood vessels is INCORRECT?
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.