CAM201: Blood Pressure Haemostasis

Question 1

What systems are involved in short and long term regulation of blood pressure?

Answer 1

Short term: Baroreflex

Long Term: Renin-Angiotensin-Aldosterone System

Question 2

Describe how the baroreflex works

Answer 2

Stretch receptors are located in the coronary sinuses and (most notable) the aortic arch.

They respond to increased or decreased stretch.

For example, with increased BP there is increased stretched, and thus there is an increased frequency in effect signals to the Cardiovascular centre in the medulla oblongata.

Increased efferent signals from baroreceptors results in increased PSNS activity and suppression of SNS activity on the heart muscles: release of acetylcholine onto anredergic receptors on cells in SA and AV nodes. This results in a negative inopropic and negative chronotropic effeect.

Decreased efferent signals from baroreceptors results increased SNS activity and suppresses PSNS activity. Result is NA/A being released onto beta receptors in heart, increasing contractility and HR.

Question 3

Describe the renin angiotensin system

Answer 3

Renin angiotensin system is responsible (along with SNS) for maintaining adequate BP.

It does this by reducing excretion of fluid in response to decreased BP.

Decreased filtration in kidney leads to release on renin from juxtaglomerular cells.

Renin converts angiotensinogen to angiotensin I in the blood.

In the lungs, ACE converts angiotensin I to Angiotensin II, which then binds to and activates AT1 and AT2 receptors.

This results in:

1) Increased secretion of Aldosterone from the adrenal cortex - Aldosterone increases Na+ resorption, decreasing urine output. It also triggers ADH which triggers thirst.
2) It increases vascular and heart hypertrophy and hyperplasia
3) Causes vasocontriction