Directed CVS Questions

Question 1

Describe the physiological significance of having the pumping chambers on the left and right sides of the heart in series.

Answer 1

The output of each side of the heart must be equal to prevent blood accumulation in the pulmonary or systemic circulations.

Question 2

Do increased pressure gradient across a vascular bed affect blood flow through it?

Answer 2

Yes, according to Darcy’s law, flow is proportional to the pressure gradient, so blood flow will increase.

Question 3

Define resistance in the context of the cardiovascular system.

Answer 3

Resistance is a measure of how difficult it is for blood to flow through the circulation, mainly controlled by arterioles.

Question 4

How does constriction of blood vessels supplying a vascular bed affect blood flow through it?

Answer 4

Blood flow will decrease as flow is inversely proportional to resistance, with vessel radius being a major factor.

Question 5

Describe the concept of capacitance in the cardiovascular system.

Answer 5

Capacitance vessels (venules and veins) can store blood, potentially containing two-thirds of the total blood volume.

Question 6

How can the body regulate blood flow through different body regions?

Answer 6

By constricting or dilating arterioles supplying different vascular beds, the body can redirect blood flow.

Question 7

Define regional distribution of blood in the context of the cardiovascular system.

Answer 7

It describes the body’s ability to constrict and dilate arterioles to redirect blood flow to different body regions.

Question 8

Define fractional distribution of blood in the context of the cardiovascular system.

Answer 8

It describes the body’s ability to constrict and dilate venules and veins to expel some blood towards the heart from their capacitance.

Question 9

What is the effect of Ca2+-channel blockers on the heart’s pumping activity?

Answer 9

Ca2+-channel blockers reduce the speed and total concentration of Ca2+ entering the cell, leading to decreased heart rate and contraction strength.

Question 10

Describe the impact of hypercalcemia on heart rate and strength of contraction.

Answer 10

Hypercalcemia increases the concentration gradient for Ca2+ entering the cell, leading to faster and increased Ca2+ entry, thereby increasing heart rate and strength of contraction.

Question 11

Define hypokalemia and its effects on myocardial cells.

Answer 11

Hypokalemia is low plasma K+ levels that can depolarize myocardial cells, causing spontaneous uncoordinated contractions similar to fibrillation.

Question 12

How does increased body temperature affect heart rate?

Answer 12

Increased body temperature speeds up chemical events, including those governing heart rate, causing a 1°C rise in body temperature to increase heart rate by about 10 bpm.

Question 13

Do high plasma K+ levels lead to heart block?

Answer 13

Yes, hyperkalemia can cause heart block by depolarizing myocardial cells, reducing the electrical gradient for positive ions, and potentially disrupting conduction through the atrioventricular node.

Question 14

Describe the function of the SA node in the heart.

Answer 14

The SA node acts as the pacemaker of the heart, initiating the electrical impulses that coordinate heart contractions.

Question 15

Match the ECG wave to the corresponding event: P wave.

Answer 15

The P wave corresponds to atrial depolarization in the heart’s electrical activity.

Question 16

Explain how the parasympathetic system affects heart rate.

Answer 16

The parasympathetic system releases acetylcholine, which hyperpolarizes pacemaker cells, reducing the slope of the pacemaker potential and slowing down heart rate (bradycardia).

Question 17

Define ejection fraction in the context of the cardiac cycle.

Answer 17

Ejection fraction is the proportion of blood pumped out of the left ventricle with each heartbeat, calculated as stroke volume divided by end-diastolic volume.

Question 18

What event occurs at point C in the cardiac cycle diagram?

Answer 18

At point C, the aortic valve opens in the cardiac cycle, allowing blood to be ejected from the left ventricle into the aorta.

Question 19

Name two factors that affect heart rate and explain their mechanisms.

Answer 19

The parasympathetic system slows heart rate by releasing acetylcholine, which hyperpolarizes pacemaker cells. The sympathetic system increases heart rate by releasing noradrenaline and adrenaline, which act on β1 receptors to enhance the pacemaker potential slope.

Question 20

Describe three factors that affect stroke volume.

Answer 20

Preload, afterload, and contractility influence stroke volume. Preload is determined by end diastolic volume, afterload by total peripheral resistance, and contractility by sympathetic stimulation.

Question 21

Explain the concept of preload in relation to stroke volume.

Answer 21

Preload is the initial stretching of the heart muscle before contraction. Increased preload leads to a stronger contraction and larger stroke volume.

Question 22

How does afterload impact stroke volume?

Answer 22

Afterload is the resistance the heart faces when contracting. Higher afterload decreases stroke volume.

Question 23

Define contractility and its role in stroke volume regulation.

Answer 23

Contractility is the heart’s ability to contract effectively. It is controlled by the sympathetic system and affects the strength of contraction for a given preload and afterload.

Question 24

What happens to end diastolic volume if venous return is not impaired but stroke volume is reduced?

Answer 24

End diastolic volume gradually increases with each heartbeat.

Question 25

How does increased end diastolic volume affect stroke volume in a compensated state after a heart attack?

Answer 25

Increased end diastolic volume increases preload, leading to an increase in stroke volume.

Question 26

In a compensated state after a heart attack, how does ejection fraction change compared to before the heart attack?

Answer 26

With increased end diastolic volume and unchanged stroke volume, ejection fraction decreases.

Question 27

Whose skeletal muscle pump works better, a skater's or a weightlifter's? Why?

Answer 27

The skater's skeletal muscle pump works better as rhythmic contractions increase preload, while sustained contractions in weightlifting reduce preload.

Question 28

How could knowledge of factors affecting venous return prevent fainting in a hot environment with a bear skin on the head?

Answer 28

Understanding factors affecting venous return can help prevent fainting by avoiding situations that lead to reduced central blood volume, which decreases preload, stroke volume, and mean arterial pressure.

Question 29

metabolic autoregulation in the context of the heart.

Answer 29

Metabolic autoregulation in the heart refers to its sensitivity to metabolites like adenosine, leading to adjustments in blood flow based on metabolic needs.

Question 30

How does the coronary circulation support the increased blood flow needed by the heart during exercise?

Answer 30

Coronary arterioles express β2 receptors, which dilate in response to sympathetic stimulation, enabling increased blood flow to the heart during exercise.

Question 31

Do changes in posture affect end diastolic volume?

Answer 31

Yes, moving to a standing position reduces end diastolic volume.

Question 32

Describe the reflex response initiated by a fall in mean arterial pressure.

Answer 32

The reflex response includes decreased vagal tone, sympathetic nervous system activation (increased HR, contractility, venoconstriction, and arteriolar constriction), aiming to increase cardiac output and total peripheral resistance.

Question 33

How does the Valsalva maneuver affect venous return and cardiac function?

Answer 33

During the maneuver, venous return to the left ventricle is reduced, but upon release, there is a significant increase in venous return and end diastolic volume, leading to increased stroke volume, cardiac output, and aortic pressure.

Question 34

Describe the effect of extended periods in zero gravity on the cardiovascular system.

Answer 34

Extended periods in zero gravity lead to an increase in central blood volume, triggering a reduction in plasma volume and potentially causing orthostatic hypotension upon return to Earth.

Question 35

How do calcium channel antagonists reduce hypertension?

Answer 35

Calcium channel antagonists block L-type calcium channels on cardiac and vascular smooth muscle cells, leading to vasodilation and reduced blood pressure.

Question 36

Define the mechanism of action of beta-adrenoceptor antagonists in reducing hypertension.

Answer 36

Beta-blockers block beta-adrenoceptors, reducing sympathetic effects on heart rate and blood pressure, ultimately lowering cardiac output and blood pressure.

Question 37

How do thiazide diuretics contribute to reducing hypertension?

Answer 37

Thiazides act on the kidney's distal tubule, inhibiting NaCl reabsorption, increasing Na+ and water excretion, and reducing plasma volume.

Question 38

Explain the role of angiotensin converting enzyme inhibitors in hypertension management.

Answer 38

Angiotensin converting enzyme inhibitors inhibit the conversion of angiotensin I to angiotensin II, leading to arteriolar dilation, decreased peripheral resistance, and venodilation.

Question 39

How do angiotensin II antagonists help in reducing hypertension?

Answer 39

Angiotensin II receptor antagonists block angiotensin II receptors, preventing vasoconstriction and producing effects similar to angiotensin converting enzyme inhibitors.