Question

What measured in the aorta (branchial artery), blood pressure is represented by both systolic and diastoic values.

A. What is responsible for each of these pressures and how do these pressures change as blood moves through the arterial network at rest?

B.What changes in the vascular network occur to cause the observed changes in pressure?

C.Can these oberved changes in pressure ensure that blood returns back to the myocardium?

D. In turn, what changes do we observe in the aortic pressure during acute forms exercise?

E. With chronic forms of exercise?

Answer 1

Question A :
Systolic Pressure :

• Systolic pressure is the maximum arterial pressure during the systole and occurs during the ventricular ejection.
• Normal systolicpressure in a young adult is 120 mmHg (range : 105-135 mmHg).
• The systolic blood pressure is the function of the cardiac output, i.e, it represents the extent of work done by the heart.

Diastolic Pressure :

• Diastolic pressure is the minimum arterial pressure during diastole and occurs just before the onset of the ventricular ejection.
• Normal diastolic pressure is 80 mmHg (range : 60-90 mmHg)
• The diastolic pressure is the function of total peripheral resistance and indicates the constant load against which the heart has to work. It undergoes much less fluctuations.

Question B :
Initially due to systole the aorta undergoes increase in radius to store the pumped blood. This causes an increase in potential energy which is stored in the walls of the aorta which is converted to kinetic energy which is transfered to the blood as kinetic energy.
The radius of the arteries also decrease as it moves away from the heart, by undergoing branching of arterial tree.
The veins have larger radius than arteries which causes a negative pressure in the veins which sucks blood from arteries and the right atrium and ventricles causes sucking effect on vena cavas. This sucks the venous blood.
This decrease in arterial radius causes increase in peripheral resistance.

Question C :
Yes. These changes ensures that the blood returns back to the myocardium, as explained in the above answer.

Question D :
In acute forms of exercise the systolic blood pressure do increases because of the increase in the heart rate.
But the diastolic blood pressure remains almost the same, because diastolic blood pressure depends on the peripheral resistance.

Question E :
During chronic exercise the systolic blood pressure increases as the heart rate increases and the diastolic blood pressure decreases. This decrease in diastolic blood pressure is due to the decrease in peripheral resistance. Decrease in peripheral resistance is in account with vasodialation caused due to the deposition of vasodialatory substances in the walls of the blood vessels.