Dr Gawad Physiology Course Online Exam - CVS – Course Lecture 5 – Cardiac Work, Cvcs Regulation

1. At rest, the left ventricular work is higher the right ventricular work because left ventricle has:

Higher volume work

Higher pressure work

Higher heart rate (more systolic contraction)

Longer diastolic time

The correct answer is "higher pressure work". The left ventricle of the heart is responsible for pumping oxygenated blood to the rest of the body, while the right ventricle pumps deoxygenated blood to the lungs. The left ventricle has thicker muscular walls compared to the right ventricle, allowing it to generate higher pressure during contraction. This higher pressure is necessary to overcome the resistance in the systemic circulation and ensure adequate blood flow to the body's organs and tissues.

Explanation

The correct answer is "higher pressure work". The left ventricle of the heart is responsible for pumping oxygenated blood to the rest of the body, while the right ventricle pumps deoxygenated blood to the lungs. The left ventricle has thicker muscular walls compared to the right ventricle, allowing it to generate higher pressure during contraction. This higher pressure is necessary to overcome the resistance in the systemic circulation and ensure adequate blood flow to the body's organs and tissues.

2. The ratio of cardiac work to the total energy expenditure is:

Called the cardiac mechanical efficiency and is normally 15%

Called the cardiac index.

Constant even during exercise.

Not changed by autonomic stimulation.

The correct answer is "Called the cardiac mechanical efficiency and is normally 15%". Cardiac mechanical efficiency refers to the ratio of cardiac work (the energy expended by the heart) to the total energy expenditure. It is commonly expressed as a percentage and is typically around 15%. This efficiency measure indicates how effectively the heart is able to convert energy into mechanical work during its pumping action. It is a constant value and is not influenced by autonomic stimulation or exercise.

Explanation

The correct answer is "Called the cardiac mechanical efficiency and is normally 15%". Cardiac mechanical efficiency refers to the ratio of cardiac work (the energy expended by the heart) to the total energy expenditure. It is commonly expressed as a percentage and is typically around 15%. This efficiency measure indicates how effectively the heart is able to convert energy into mechanical work during its pumping action. It is a constant value and is not influenced by autonomic stimulation or exercise.

3. In case of hemorrhage, the carotid body chemoreceptors:

Have no effect on heart rate

Try to decrease COP.

Increase the arterial B.P.

Produce heart block.

The carotid body chemoreceptors play a role in regulating blood pressure. In the case of hemorrhage, these chemoreceptors detect the decrease in blood pressure and respond by increasing the arterial blood pressure. This response helps to compensate for the loss of blood by constricting blood vessels and increasing the heart rate, ultimately maintaining adequate blood flow to vital organs. Therefore, the correct answer is that the carotid body chemoreceptors increase the arterial blood pressure in the event of hemorrhage.

Explanation

The carotid body chemoreceptors play a role in regulating blood pressure. In the case of hemorrhage, these chemoreceptors detect the decrease in blood pressure and respond by increasing the arterial blood pressure. This response helps to compensate for the loss of blood by constricting blood vessels and increasing the heart rate, ultimately maintaining adequate blood flow to vital organs. Therefore, the correct answer is that the carotid body chemoreceptors increase the arterial blood pressure in the event of hemorrhage.

4. Sympathetic V.C. tone is decreased in response to increased activity of the:

Carotid sinus baroreceptors.

Medullary chemoreceptors.

Carotid body chemoreceptors.

All of the above.

None of the above.

The sympathetic V.C. (vasoconstrictor) tone is decreased in response to increased activity of the carotid sinus baroreceptors. These baroreceptors are located in the carotid sinuses, which are dilations in the carotid arteries near the base of the neck. They detect changes in blood pressure and send signals to the brainstem to regulate sympathetic nervous system activity. When blood pressure increases, the baroreceptors are stimulated, leading to a decrease in sympathetic vasoconstrictor tone, which helps to lower blood pressure. Therefore, the increased activity of carotid sinus baroreceptors is responsible for the decreased sympathetic V.C. tone.

Explanation

The sympathetic V.C. (vasoconstrictor) tone is decreased in response to increased activity of the carotid sinus baroreceptors. These baroreceptors are located in the carotid sinuses, which are dilations in the carotid arteries near the base of the neck. They detect changes in blood pressure and send signals to the brainstem to regulate sympathetic nervous system activity. When blood pressure increases, the baroreceptors are stimulated, leading to a decrease in sympathetic vasoconstrictor tone, which helps to lower blood pressure. Therefore, the increased activity of carotid sinus baroreceptors is responsible for the decreased sympathetic V.C. tone.

5. A decline in the arterial blood pressure causes:

Slowing of the heart rate.

Stimulation of rostral ventolateral nucleus

Stimulation of the atrial stretch receptors

Stimulation of the chemoreceptors if BP is between 90-120 mmHg

A decline in arterial blood pressure can stimulate the rostral ventolateral nucleus. This nucleus is involved in regulating sympathetic outflow, which can lead to increased heart rate and vasoconstriction, ultimately helping to restore blood pressure to normal levels.

Explanation

A decline in arterial blood pressure can stimulate the rostral ventolateral nucleus. This nucleus is involved in regulating sympathetic outflow, which can lead to increased heart rate and vasoconstriction, ultimately helping to restore blood pressure to normal levels.