Question 1

The ESV of the heart averages about 140 mL.

Accepted Answer

The average ESV (end-systolic volume) of a healthy heart is around 50-60 mL.

Question 2

Most blood flow through the coronary vessels occurs during ventricular systole when the heart is driving blood forward.

Accepted Answer

The answer of Most blood flow through the coronary vessels...

Question 3

Parasympathetic stimulation of the AV node increases the speed of transmission of the impulse through the AV node.

Accepted Answer

The answer of Parasympathetic stimulation of the AV node increases...

Question 4

The average resting heart rate is normally established by the rhythm of the AV node.

Accepted Answer

The average resting heart rate is established by the sinoatrial (SA) node, which is the natural pacemaker of the heart. The SA node initiates the electrical impulses that cause the heart to contract and pump blood. The AV node is responsible for conducting the electrical impulses from the atria to the ventricles, but it does not establish the resting heart rate.

Question 5

According to the Frank-Starling law of the heart,the greater the stroke volume,the smaller the subsequent end-diastolic volume will be,because as more blood is squeezed out,the heart cannot fill as completely during the next diastole.

Accepted Answer

The statement is incorrect. According to the Frank-Starling law of the heart, the greater the end-diastolic volume, the greater the stroke volume. This is due to the fact that a larger preload (end-diastolic volume) stretches the myocardium, causing a more forceful contraction and therefore a larger stroke volume.

Question 6

Stroke volume is determined by the extent of venous return and parasympathetic activity.

Accepted Answer

Stroke volume is primarily determined by the extent of venous return and sympathetic activity, not parasympathetic activity.

Question 7

Stroke volume can vary by alterations in both intrinsic and extrinsic control mechanisms.

Accepted Answer

Stroke volume can be affected by factors such as preload, contractility, and afterload (intrinsic control) as well as by neural and hormonal influences (extrinsic control). Therefore, stroke volume can vary by alterations in both intrinsic and extrinsic control mechanisms.

Question 8

According to the Frank-Starling law of the heart,the shorter the initial length of the cardiac muscle fibres prior to contraction,the more forceful will be the subsequent contraction because the fibres are already partially contracted.

Accepted Answer

According to the Frank-Starling law of the heart, the longer the initial length of the cardiac muscle fibres prior to contraction, the more forceful will be the subsequent contraction because there is an optimal overlap between actin and myosin filaments. When the muscle fibres are already partially contracted, they have less room to contract further, resulting in a less forceful contraction.

Question 9

Angina pectoris develops from the abundance of oxygen of blood in the coronary circulation.

Accepted Answer

Angina pectoris develops from a lack of oxygen in the heart muscle, which is typically caused by narrowing or blockages in the coronary arteries that supply blood to the heart.

Question 10

Cardiac output is stroke volume times the heart rate.

Accepted Answer

This is a true statement. Cardiac output is the amount of blood pumped by the heart in one minute, and it is determined by multiplying the amount of blood pumped with each beat (stroke volume) by the number of beats per minute (heart rate).

Question 11

Increased EDV results in decreased stroke volume.

Accepted Answer

Increased EDV (end-diastolic volume) actually usually results in increased stroke volume, due to the Frank-Starling mechanism.

Question 12

The cardiac output is the same as the cardiac reserve of the heart.

Accepted Answer

The cardiac output is the amount of blood that is pumped out by the heart in one minute, whereas the cardiac reserve is the difference between the maximum cardiac output and the resting cardiac output. Therefore, they are not the same thing.

Question 13

The amount of blood pumped out of the heart during each beat is known as the cardiac output.

Accepted Answer

The answer of The amount of blood pumped out of...

Question 14

Left-sided congestive heart failure can lead to pulmonary edema.

Accepted Answer

Left-sided congestive heart failure can cause fluid to accumulate in the lungs, resulting in pulmonary edema.

Question 15

Sympathetic stimulation of the heart increases calcium permeability.

Accepted Answer

Sympathetic stimulation increases calcium permeability of the heart, leading to an increase in contractility and heart rate.

Question 16

Cardiac muscle receives its blood supply primarily during ventricular systole when blood is being pumped out into the aorta.

Accepted Answer

Cardiac muscle receives its blood supply primarily during diastole when the heart is relaxed and filling with blood. This is because during systole, the contraction of the heart muscle compresses the blood vessels, making it difficult for blood to flow into them.

Question 17

Parasympathetic stimulation slows the rate of depolarization of the SA node and thus decreases the heart rate.

Accepted Answer

Parasympathetic stimulation releases acetylcholine which binds to receptors on the SA node, causing an increase in potassium permeability and thus hyperpolarizing the cell. This slows the rate of depolarization and decreases the heart rate.

Question 18

The heart muscle receives its oxygen and nutrients directly from the blood within its chambers during ventricular diastole.

Accepted Answer

The answer of The heart muscle receives its oxygen and...

Question 19

The EDV of the heart averages about 65 mL.

Accepted Answer

The End-Diastolic Volume (EDV) of the heart averages about 120 mL in a typical adult, not 65 mL. EDV refers to the volume of blood in the ventricle at the end of diastole, just before the heart contracts.

Question 20

Sympathetic stimulation increases the heart rate.

Accepted Answer

Sympathetic stimulation is known to increase heart rate by releasing norepinephrine and epinephrine which bind to beta receptors in the heart and increase contractions.

Quiz 7: Cardiac Physiology