Question

Discuss briefly the mechanisms that regulate arterial blood pressure including the sympathetic nervous system, the renin–angiotensin–aldosterone system (RAAS), and renal function.

Answer 1

Arterial blood pressure controlled by-

1. Sympathetic nervous system:-

Decreased arterial pressure is detected by baroreceptors, which then trigger a sympathetic response. This stimulates an increase in heart rate and cardiac contractility leading to an increased blood pressure.

2. RAAS:-

The renin-angiotensin system or RAS regulates blood pressure and fluid balance in the body. When blood volume or sodium levels in the body are low, or blood potassium is high, cells in the kidney release the enzyme, renin. Renin converts angiotensinogen, which is produced in the liver, to the hormone angiotensin I. An enzyme known as ACE or angiotensin-converting enzyme found in the lungs metabolizes angiotensin I into angiotensin II. Angiotensin II causes blood vessels to constrict and blood pressure to increase. Angiotensin II stimulates the release of the hormone aldosterone in the adrenal glands, which causes the renal tubules to retain sodium and water and excrete potassium. Together, angiotensin II and aldosterone work to raise blood volume, blood pressure and sodium levels in the blood to restore the balance of sodium, potassium, and fluids. If the renin-angiotensin system becomes overactive, consistently high blood pressure results.

Contribution of renal-

Aldosterone causes the tubules of the kidneys to increase the reabsorption of sodium and water into the blood. This increases the volume of fluid in the body, which also increases blood pressure. If the renin-angiotensin-aldosterone system is too active, blood pressure will be too high.