Week 6 Formative Quiz questions Flashcards

1
Q

Regarding control of the peripheral circulation: Circulating adrenaline causes arteriolar constriction in all body regions.

A

False. Whilst adrenaline activates alpha 1 receptors and causes arteriolar constriction in the vast majority of body regions, there are notable exceptions. These are the skeletal muscle and cardiac muscle which also express beta 2 receptors which cause arteriolar dilation and swamp the alpha 1 receptor mediated constriction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Concerning the cardiac cycle: At resting heart rate, systole takes approximately twice as long as diastole.

A

False. At resting heart rate, systole takes about 1/3rd of the cardiac cycle, ie it is half as long as diastole. At higher heart rates, most of the time is taken out of diastole and so systole takes a proportionally greater proportion of the cycle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Concerning the electrical activity of the heart: Cells of the myocardium are electrically connected via gap junctions.

A

True. Cells of the myocardium are both electrically connected (via gap junctions) and physically connected (via the desmosomes). Hence it acts as functional syncytium which depolarizes as one, and contracts as one.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Concerning the electrical activity of the heart: A gradual opening of leaky K+ channels contributes to the pacemaker potential.

A

False. A gradual closing of K+ channels is one of the factors that contributes to the pacemaker potentials – the others being opening of the “funny” Na+ channels and T-type Ca2+ channels. Gradual opening of K+ channels would hyperpolarize the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Concerning the cardiac cycle: The left atrial pressure rises at the start of systole.

A

True. When the ventricle contacts, the mitral and tricuspid valves close and then bulge into the atria, creating the a wave on the atrial pressure trace, which terminates when the aortic and pulmonary valves open.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Concerning the cardiovascular system: Mean arterial pressure (MAP) is calculated by measuring the pressure in all the arteries of the systemic circulation and taking the average.

A

False. Pressure in all systemic arteries is approximately the same. The mean arterial pressure describes the average pressure in the arteries throughout the cardiac cycle. This is approximately equal to the diastolic pressure plus a third of the pulse pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Concerning the vascular system: Most arterioles are innervated only by parasympathetic nerves.

A

False. Most blood vessels are innervated only by sympathetic vessels. These release noradrenaline which activates alpha 1 receptors and causes vasoconstriction. Most vessels are not innervated by the parasympathetic system. The genitalia and salivary glands are the exceptions that prove the rule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Concerning the cardiac cycle: The stroke volume of the right ventricle is approximately one fifth of that of the left ventricle.

A

False. The right and left sides of the heart lie in series and must have the same cardiac output or blood will accumulate in the systemic or pulmonary circulations. They have the same heart rate because they share the same pacemaker, so the stroke volume must also be the same. If you got it wrong you were probably thinking of the pressure evoked by the left ventricle, which is about one fifth of that of the left.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Concerning the vascular system: Local arteriolar dilation, as occurs in exercising muscle, may cause oedema.

A

True. Arteriolar dilation will increase the hydrostatic pressure in downstream capillaries and increase the amount of fluid that is filtered out through Starling’s forces.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Concerning the electrical activity of the heart: The PR interval gives a good indication of the time taken for the spread of depolarisation across the atria.

A

False. The PR interval indicates the time between the start of atrial depolarization and the start of ventricular depolarization. This includes the time for depolrisation to spread across the atria, but it is mostly due to the slow conduction through the atrioventricular node.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Concerning the pumping ability of the heart: Stimulation of sympathetic fibres innervating the heart increases contractility.

A

True. Noradrenaline acting on beta1 receptors increases excitation-contraction coupling and gives a stronger contraction for any given preload.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Concerning the cardiac cycle: End systolic volume of the ventricle is approximately 0ml.

A

False. End systolic volume will vary from person to person but is likely to be closer to 60ml. If end systolic volume was 0ml, increased strength of contraction could not increase stroke volume.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Concerning the cardiac cycle: The second heart sound is caused by closure of the aortic and pulmonary valves

A

True. The normal heart sounds are caused by turbulence in the blood as the mitral and tricuscpid, and then the aortic an pulmonary valves close.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Concerning the electrical activity of the heart: The plateau phase of the cardiac action potential is maintained by entry of Na+ ions.

A

False. The initial fast depolarising phase of the non-pacemaker potential is mediated by voltage gated Na+ channels, but the plateau phase is mediated by L-type voltage gated Ca2+ channels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Concerning the electrical activity of the heart: The QRS complex immediately precedes ventricular contraction.

A

True. The QRS complex is created by the wave of depolarization spreading through the ventricle, which in turn triggers ventricular contraction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Concerning the cardiac cycle: The left ventricular pressure is approximately 80 mmHg during diastole.

A

False. During diastole (the filling phase), the pressure in the left ventricle is very low – maybe even 0mmHg.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Concerning the electrical activity of the heart: The Q-T interval gives a rough indication of the duration of ventricular systole.

A

True. The Q-T interval indicates the time between ventricular depolarisation and ventricular repolarisation, ie the length of the ventricular action potential. This is approximately the same as the length of the contraction evoked and therefore the duration of systole.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Regarding control of the peripheral circulation: Increasing the radius of an arteriole 2-fold, increases its resistance 16-fold.

A

False. Close. Varying radius does alter resistance to the power of 4, but increasing radius will reduce resistance, not increase it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Concerning the cardiac cycle: The aortic valve is closed throughout diastole.

A

True. It prevents the flow of blood back in from the high pressure aorta during the ventricular filling phase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Concerning the electrical activity of the heart: Hyperkalemia (a high concentration of K+ in the plasma) is liable to cause fibrillation of the myocardium.

A

True. Hyperkalemia will depolarise myocardial cells so that they approach threshold and randomly fire action potentials and contract rather than waiting for appropriate depolarization via the special conducting system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Concerning the vascular system: The major resistance to blood flow is produced by the arteries.

A

False. The arteries have a wide lumen and therefore a low resistance. The major resistance is created by the arterioles with their relatively narrow lumen and thick contractile wall.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

The T-wave of the ECG is positive going in standard limb lead II because the action potential in endocardial cells is longer than the action potential in epicardial cells.

A

True. This explains why the main vector of depolarisation spreads down the ventricle, but the main vector of repolarization spreads in the opposite direction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Regarding control of the peripheral circulation: Metabolic autoregulation is a mechanism which matches the metabolic rate of a body region to its energy reserves.

A

False. Metabolic autoregulation is a mechanism that matches the blood flow of a body region to its metabolic demands.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Concerning the vascular system: Rhythmic contraction of skeletal muscle promotes venous return.

A

True. This the action of the skeletal muscle pump. It is one of several mechanism that increase venous pressure and venous return during exercise and therefore offset the reduction in end diastolic volume caused by heart heart rates. The others include the respiratory pump, venomotor tone, and increased systemic filling pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Concerning the electrical activity of the heart: The refractory period of the action potential is much shorter than the contraction it produces.

A

False. Unlike skeletal muscle, because of its long action potential the refractory period of cardiac muscle is almost as long as the twitch contraction it evokes. The result is that the cardiac muscle must relax before it can contract again. It cannot exhibit a tetanic contraction.

26
Q

Concerning the vascular system: Blood velocity is lowest in the capillaries.

A

True. Blood velocity is related to total cross-sectional area of the vessels. The aorta has a low total cross-sectional area and the blood velocity must therefore be very fast. The total cross-sectional area of the capillaries is massive and velocity of blood flow through them is therefore very slow.

27
Q

Concerning the pumping ability of the heart: Cutting the sympathetic and parasympathetic innervation of the sinoatrial node will cause an increase in resting heart rate.

A

True. The fastest (and therefore the) pacemaker cells of the heart have an inherent rate of about 100 beats per minute. This can be speeded up by the sympathetic system or slowed down by the parasympathetic system. At rest, the parasympathetic system dominates and so the heart is said to be under vagal restraint, giving the resting heart rate of about 70 beats per minute.

28
Q

Concerning the cardiac cycle: The first heart sound is caused by opening of the mitral and tricuspid valves.

A

False. Opening of the valves does not evoke any heart sounds in health.

29
Q

Concerning the vascular system: A low concentration of protein in the blood (hypoproteinemia) may cause oedema.

A

True. In the periphery water is lost from the capillaries through the hydrostatic pressure gradient. This creates an osmotic gradient in the opposite direction which draws water back into the capillary. If the concentration of protein in the plasma is low, this osmotic gradient cannot develop and so less fluid is re-absorbed.

30
Q

Concerning the cardiac cycle: The second heart sound is heard at the start of diastole.

A

True. The first heart sounds is caused by the mitral and tricuscpid valves closing at the start of systole, and the second is caused by the aortic and pulmonary valves closing at the start of diastole

31
Q

Regarding control of the peripheral circulation: The injury response depends on intact nociceptive nerve function.

A

True. The injury response depends on action potentials invading the terminals of nociceptive C-fibres and triggering the release of substance P.

32
Q

Concerning the cardiac cycle: A systolic murmur could be caused by regurgitation of blood through the aortic valve.

A

False. A murmur is generally caused by turbulence in the blood due to regurgitation through a valve that should be closed, or stenosis (narrowing) of a valve that should be open. During systole the aortic valve is open so a systolic murmur could be due to stenosis of the aortic valve. Regurgitation through the aortic valve would cause a diastolic murmur.

33
Q

Regarding control of the peripheral circulation: Smooth muscle in the walls of capillaries controls their blood flow by constriction and relaxation to vary resistance.

A

False. The capillaries have no smooth muscle and cannot vary their resistance. Instead it is the job of the upstream arterioles (the resistance vessels) to control blood flow.

34
Q

Concerning the pumping ability of the heart: Increased venous return causes an increased stroke volume.

A

True. In vivo, increased venous return during the filling phase increases end diastolic volume which increases preload on the heart. Starling’s law tells you that this will cause an increased strength of contraction and therefore increases stroke volume.

35
Q

Concerning the arterial baroreflex: Sensory information from the arterial baroreceptors is primarily concerned with regulation of mean arterial pressure in the short, rather than the long, term.

A

True. Cutting the sensory nerves from the aortic and arch and carotid sinus baroreceptors results in loss of short-term, but not long-term, control of blood pressure. Long term control of blood pressure may rely more on sensory input from the cardiopulmonary baroreceptors.

36
Q

Concerning the cardiovascular system: Cardiac output at rest is approximately 75ml/beat.

A

False. 1. This is a good figure for the stroke volume, but the cardiac output is the volume of blood pumped out per minute. This is likely to be about 5 litres per min.

37
Q

Concerning the cardiovascular system: The circular smooth muscle of arterioles controls peripheral resistance under the influence of the sympathetic nervous systems

A

True. The arterioles are indeed the resistance vessels. The smooth muscle surrounding them is controlled by intrinsic mechanisms, but also by central mechanisms. Notably the sympathetic nerves which innervate the arterioles and release noradrenaline, and adrenaline which is released from the adrenal medulla. Both of these activate alpha 1 receptors on the smooth muscle which causes arteriolar constriction and regulates peripheral resistance.

38
Q

Concerning the vascular system: Most vascular beds are arranged in parallel.

A

True. The significance of this being that all body regions receive fresh oxygenated blood, and that the cardiac output can be redirected between different body regions when required.

39
Q

The PR interval is normally under 0.2 seconds.

A

True. The PR interval represents the time between the start of atrial depolarization and the start of ventricular depolarisation. Most of this is taken up by conduction through the atrio-ventricular node. An interval of over 0.2 seconds indicates that this is impaired and is classed as 1st degree heart block.

40
Q

Concerning the arterial baroreflex: A fall in baroreceptor firing rate triggers a reflex increase in sympathetic outflow.

A

True. A fall in baroreceptor firing rate signals a fall in mean arterial pressure which triggers (amongst other things) an increase in sympathetic outflow. This will increase heart rate, increase stroke volume, cause venoconstriction and cause arteriolar constriction, all of which will contribute a pressor response - ie an increase in blood pressure.

41
Q

Concerning the cardiovascular system: The mean arterial pressure (MAP) in the aorta is approximately equal to the mean arterial pressure in the pulmonary trunk.

A

False. The pressure evoked in the pulmonary circulation by the right side of the heart is about 1/5th of that evoked in the systemic circulation by the left side of the heart.

42
Q

Concerning the cardiovascular system: MAP = CO x TPR

A

True. Another way of looking at this is that the pressure in the arteries is affected by how much blood is pushed into them (the cardiac output), and how easy it is for the blood to get out (the total peripheral resistance). This is also referred to as the fundamental equation of cardiovascular physiology because the body spends so much time monitoring MAP and adjusting CO and TPR accordingly.

43
Q

Concerning the cardiac cycle: Most of the stroke volume leaves the ventricle during the first third of systole.

A

True. This is the rapid ejection phase.

44
Q

Concerning the electrical activity of the heart: Cardiac contraction is initiated by sympathetic nerves.

A

False. The heart has its own inherent rhythm that is normally set by the pacemaker cells in the sinoatrial node. It can be slowed down by the parasympathetic system and speeded up by the sympathetic system, but it does not rely on these to initiate the heart beat.

45
Q

Concerning the electrical activity of the heart: The atrioventricular node is the only electrically conducting region connecting the atria and the ventricles.

A

True. The atria and the ventricles are separated by the non-conducting annulus fibrosus, except for the very slow-conducting atrioventricular node.

46
Q

Concerning the vascular system: The smooth muscle surrounding the arterioles of the coronary circulation expresses beta 2 receptors.

A

True. The heart and skeletal muscle are two locations in which the smooth muscle surrounding arterioles expresses many beta 2 receptors. These are coupled to second messenger pathways that relax the smooth muscle and therefore cause arteriolar dilation. This increases blood flow and contributes to the redirection of blood flow to these areas during exercise.

47
Q

Concerning the electrical activity of the heart: The fastest depolarising pacemaker potentials in the heart are usually found in the cells of the sinoatrial node.

A

True. Many myocardial cells show some pacemaker activity, but the fastest pacemakers will set the rate for all the rest, and these are normally in the sino-atrial node.

48
Q

Regarding control of the peripheral circulation: Arterioles in most organs constrict in response to local hypoxia.

A

False. In most body regions, hypoxia is taken as a sign that that region needs more blood and so causes arteriolar dilation. The pulmonary circulation is the exception, where blood is redirected to the better ventilated parts of the lung which maximises ventilation-perfusion matching.

49
Q

Regarding control of the peripheral circulation: The endothelium has an important role in the control of the peripheral circulation.

A

True. Endothelial cells have a key role in sensing metabolite concentrations and releasing autocrine agents such as EDRF (NO) to enable the intrinsic control of blood flow in a vascular bed.

50
Q

Concerning the arterial baroreflex: Rising from a sitting to a standing position will cause a reflex increase in heart rate and total peripheral resistance.

A

True. But do you understand the mechanism? Standing causes pooling of blood in the venules of the feet and legs. This reduces end diastolic volume and therefore preload, stroke volume, cardiac output and mean arterial pressure. This fall in blood pressure is sensed by the arterial baroreceptors which trigger a reflex increase in, amongst other things, heart rate and total peripheral resistance to restore blood pressure.

51
Q

Regarding control of the peripheral circulation: Increasing the radius of an arteriole 2-fold, increases its resistance 16-fold.

A

False. Close. Varying radius does alter resistance to the power of 4, but increasing radius will reduce resistance, not increase it.

52
Q

Concerning the electrical activity of the heart: Hyperkalemia (a high concentration of K+ in the plasma) is liable to cause fibrillation of the myocardium.

A

True. Hyperkalemia will depolarise myocardial cells so that they approach threshold and randomly fire action potentials and contract rather than waiting for appropriate depolarization via the special conducting system.

53
Q

Concerning the cardiac cycle: The second heart sound is caused by closure of the aortic and pulmonary valves

A

True. The normal heart sounds are caused by turbulence in the blood as the mitral and tricuscpid, and then the aortic an pulmonary valves close.

54
Q

Concerning the vascular system: A low concentration of protein in the blood (hypoproteinemia) may cause oedema.

A

True. In the periphery water is lost from the capillaries through the hydrostatic pressure gradient. This creates an osmotic gradient in the opposite direction which draws water back into the capillary. If the concentration of protein in the plasma is low, this osmotic gradient cannot develop and so less fluid is re-absorbed.

55
Q

Concerning the arterial baroreflex: A fall in baroreceptor firing rate triggers a reflex increase in sympathetic outflow.

A

True. A fall in baroreceptor firing rate signals a fall in mean arterial pressure which triggers (amongst other things) an increase in sympathetic outflow. This will increase heart rate, increase stroke volume, cause venoconstriction and cause arteriolar constriction, all of which will contribute a pressor response - ie an increase in blood pressure.

56
Q

Concerning the cardiac cycle: End systolic volume of the ventricle is approximately 0ml.

A

False. End systolic volume will vary from person to person but is likely to be closer to 60ml. If end systolic volume was 0ml, increased strength of contraction could not increase stroke volume.

57
Q

Concerning the cardiovascular system: Cardiac output at rest is approximately 75ml/beat.

A

False. 1. This is a good figure for the stroke volume, but the cardiac output is the volume of blood pumped out per minute. This is likely to be about 5 litres per min.

58
Q

Concerning the cardiac cycle: The second heart sound is heard at the start of diastole.

A

True. The first heart sounds is caused by the mitral and tricuscpid valves closing at the start of systole, and the second is caused by the aortic and pulmonary valves closing at the start of diastole

59
Q

Concerning the electrical activity of the heart: A gradual opening of leaky K+ channels contributes to the pacemaker potential.

A

False. A gradual closing of K+ channels is one of the factors that contributes to the pacemaker potentials – the others being opening of the “funny” Na+ channels and T-type Ca2+ channels. Gradual opening of K+ channels would hyperpolarize the cell.

60
Q

The T-wave of the ECG is positive going in standard limb lead II because the action potential in endocardial cells is longer than the action potential in epicardial cells.

A

True. This explains why the main vector of depolarisation spreads down the ventricle, but the main vector of repolarization spreads in the opposite direction.