Hormones in Fluid Regulation: Aldosterone, ADH, ANP, BNP (RAAS, Thirst Mechanism)

What is the role of hormones in fluid regulation?

Hormones help maintain water balance in the body, preventing fluid volume overload and deficit.

What hormones are involved in fluid regulation?

Aldosterone, Antidiuretic hormone (ADH), Atrial natriuretic peptide (ANP), Brain natriuretic peptide (BNP), and the Renin-angiotensin-aldosterone system (RAAS).

What triggers the activation of the Renin-angiotensin-aldosterone system (RAAS)?

A drop in blood pressure due to fluid volume deficit.

What is the primary goal of the RAAS?

To increase blood pressure by increasing blood volume.

What hormone is created by the RAAS that activates aldosterone and ADH?

Angiotensin II.

What are the effects of Angiotensin II?

It causes vasoconstriction, stimulates thirst, and activates aldosterone and ADH.

What is the sequence of events in the RAAS?

1. Drop in blood pressure. 2. Kidneys release renin. 3. Liver activates angiotensinogen to Angiotensin I. 4. ACE converts Angiotensin I to Angiotensin II.

How does aldosterone affect the kidneys?

It causes the kidneys to retain sodium and water, decreasing urination.

What is the function of Antidiuretic hormone (ADH)?

ADH causes the kidneys to retain water, increasing blood volume.

What initiates the thirst mechanism?

Low fluid levels in the body lead to high plasma osmolality.

What role do osmoreceptors in the hypothalamus play in fluid regulation?

They detect high plasma osmolality and trigger the release of ADH.

What happens in the kidneys when ADH is present?

The distal convoluted tubule and collecting duct reabsorb water, adding it back to the bloodstream.

What are natriuretic peptide hormones and their function?

Hormones that oppose the effects of Angiotensin II, stopping the actions of aldosterone and ADH to prevent fluid overload.

What triggers the release of Atrial natriuretic peptide (ANP)?

Stretching of the atrial walls in the heart.

What triggers the release of Brain natriuretic peptide (BNP)?

Stretching of the ventricular walls in the heart.

What is the overall effect of ANP and BNP on fluid balance?

They help reduce fluid volume by inhibiting the effects of aldosterone and ADH.

What is the consequence of low fluid in the body?

It leads to high plasma osmolality and triggers the thirst mechanism.

How does the body respond to high plasma osmolality?

The hypothalamus releases ADH, stimulating thirst and water retention.

What is the end goal of the thirst mechanism?

To add water back to the body and correct fluid volume deficit.

What happens to plasma osmolality when water is retained?

It lowers to normal levels.

What is the relationship between fluid volume and blood pressure?

Low fluid volume can lead to low blood pressure, which the body seeks to correct.

What is the significance of the kidneys in fluid regulation?

They respond to hormones like ADH and aldosterone to regulate water and sodium retention.