Question

1. What happens to reabsorption at the capillaries as hydrostatic pressure changes?

2. If venous return to the heart decreases, what happens ro cardiac output and why?

3. How does thw autonomic nervous system system affect blood pressure?

4. What are baroreceptoes? Where are they located? How do they work?

Answer 1

1) Hydrostatic pressure is the pressure of any fluid enclosed in a space. In other words, it is the pressure exerted by a fluid, due to the gravitational force, at a given point within the fluid.

Hydrostatic pressure helps the fluid to move out of capillary. It is the primary driving force in the fluid transport between the capillary and tissues.

Whereas osmotic pressure pulls back the fluid into the capillaries.

As the hydrostatic pressure in capillaries increase it forces the fluid to move out to tissues and this increase the hydrostatic pressure in interstitial fluid.

Osmotic pressure allows the fluid back into the capillaries. And it works with a principle of movement based on the difference in concentration gradient.

2) venous return is the amount of blood returns, from the body, back into the heart. It directly affects the cardiac output.

When the venous return decreases ( due to increased vascular resistance or venacaval compression ), it decreases the stroke volume and thereby decreases cardiac output.

3) ANS ( Autonomic-nervous system) plays an important role in the regulation of blood pressure. The sympathetic pathway get activated under stress and thereby increase blood pressure and heart rate, also it constricts blood vessels. It occurs in response to the transient changes in the arterial pressure which is detected by the baroreceptors in the vessels.

4) Baroreceptors are specialized nerve endings that are located in the blood vessels which senses the changes in the blood pressure and thereby helps in the regulation of blood pressure.

Baroreceptors are located in the carotid sinus and in the aortic arch. It senses the pressure variation and enhance the tone of smooth muscles. It responds to the change in the t nsion of the arterial wall.

When the BP increases the Baroreceptors detects and it stretches and send signal to the vasomotor centre of the brain. It inhibits the sympathetic pathway, and thus increase vagal tone which cause a decrease in the heart rate. Thereby the BP decreases

When the BP decreases, Baroreceptors detects, it causes the vasomotor centre to uninhibit the sympathetic activity in the heart and blood vessels, thereby decreases vagal tone. This causes an increase in blood pressure.