GFR Regulation

What triggers the myogenic mechanism?

Changes in blood pressure stretching the afferent arteriole

What happens when blood pressure increases?

Afferent arteriole constricts → prevents too much GFR

What happens when blood pressure decreases?

Afferent arteriole dilates → maintains GFR

What structure senses changes in filtrate flow?

Macula densa

What does high NaCl in filtrate indicate?

GFR is too high

How does the kidney respond to high NaCl?

Constrict afferent arteriole → decrease GFR

What does low NaCl in filtrate indicate?

GFR is too low

How does the kidney respond to low NaCl?

Dilate afferent arteriole + release renin → increase GFR

What triggers Angiotensin II release?

Low blood pressure or low NaCl

How does Angiotensin II affect GFR?

Constricts efferent arteriole → increases GFR (maintains filtration)

What triggers ANP release?

High blood volume / pressure

How does ANP affect GFR?

Dilates afferent arteriole → increases GFR → more urine

When is the sympathetic nervous system activated?

Stress, blood loss, or low blood pressure

How does sympathetic activity affect GFR?

Constricts afferent arteriole → decreases GFR

What is aldosterone's main function?

Increase Na⁺ reabsorption (and water follows)

Where does aldosterone act?

Distal tubule & collecting duct

What is the overall effect of aldosterone?

Increases blood volume and blood pressure

What triggers ADH release?

High osmolarity or low blood volume

What does ADH do?

Increases water reabsorption in collecting ducts

What is the overall effect of ADH?

Decreases urine output, increases blood volume

What is ANP's main role as a hormone?

Promote Na⁺ and water excretion

What is the overall effect of ANP on blood volume?

Decreases blood volume and pressure