Question

3. Considering the cardiovascular system.

a) Write the formula relating cardiac output, heart rate, and stroke volume. And indicate the normal values of cardiac output, stroke volume and heart rate of a resting adult.

b) A man was hurt in a car accident with heavy bleeding. I. State the change in blood volume with heavy bleeding.

II. Predict and briefly explain the possible change in cardiac output and blood pressure of that man.

III. The man has a very high heart rate with heavy bleeding. Why?

Answer 1

Answer 3 (a) Cardiac output is known as heart output. It is a term used in cardiac physiology which describes the volume of blood being pumped by the heart by the left and right ventricle per unit time. It is the product of heartbeat per minute and the stroke volume.

CO = HR x SV

The normal values for a resting adult are:

Cardiac output = 5 l/min

Heartbeat rate = 70 beats/min

Stroke volume = 70 ml.

(b) I. Heavy bleeding leads to a change in the volume of blood. Due to excessive bleeding loss of red blood cells takes place which can lead to further complications and finally death.

" As the blood loss volume is not mentioned, we can only mention the effect of blood loss.

ll. As the cardiac output is the heart output. So, when the body is suffering from blood loss, then the cardiac output will also be affected. The cardiac output will decrease and the blood pressure as well.

lll. The reason behind the high heart rate is the decreased blood volume caused by blood loss. The blood loss will reduce cardiac output and arterial pressure. So, as to bring the arterial pressure and cardiac output normal heart tries to pump more blood and that's why the heart rate increases.