F+E- Highlights: RAAS + ADH Hormone + Thirst

What happens when the kidneys sense low perfusion or low blood pressure?

They secrete renin from the juxtaglomerular apparatus, activating the renin–angiotensin–aldosterone system (RAAS).

Why is the renin–angiotensin–aldosterone system (RAAS) important?

It is one of the body’s most important compensatory mechanisms for maintaining fluid balance.

What does renin do after it is secreted by the kidneys?

Renin circulates to the liver and converts angiotensinogen, a protein produced by the liver, into angiotensin I.

What is the role of angiotensin-converting enzyme (ACE) in the RAAS?

ACE converts angiotensin I to angiotensin II.

What effect does angiotensin II have on the arteries and blood pressure?

Angiotensin II causes potent peripheral arterial vasoconstriction, which increases arterial blood pressure. It also stimulates the adrenal gland to secrete aldosteron

What effect does aldosterone have at the nephron?

increases sodium and water reabsorption into the bloodstream. This raises blood volume and blood pressure. Aldosterone also stimulates the secretion of potassium into the nephron tubules, which in turn causes potassium excretion by the kidney

Which two mechanisms help maintain sodium concentration and stimulate oral fluid intake?

ADH and the thirst mechanism.

What part of the brain controls oral fluid intake through the thirst mechanism?

The thirst center in the hypothalamus.

What stimulates thirst, and how does the body respond?

Increased serum osmolality or decreased blood volume stimulates hypothalamic neurons through intracellular dehydration, triggering thirst and increased oral fluid intake.

What happens when the brain senses increased osmolality?

The posterior pituitary is stimulated to release ADH.

What effect does ADH have on the kidney nephrons?

ADH increases water reabsorption into the bloodstream.

How does ADH affect blood volume and urine output?

ADH raises blood volume and decreases urine output.