L3: Urination & Filtration

summary:

myogenic mechanism

-FAST (ms to s)

-independent of nn and hormones

-autoregulatory to maintain GFR despite BP changes

-in the afferent arteriole (a into glomerulus)

general mechanism:

myogenic mechanism

inc arterial P → wall stretch

• sm m constricts → dec blood into glomerulus → GFR does not rise

dec arterial P → less stretch

• sm m relaxes → dilation more blood into glomerulus → GFR does not fall

importance:

myogenic mechanism

-protects glomerular capillaries from P damage

-prevents excessive fluid loss/waste retention

What is the difference between tubuloglomerular feedback (TGF) and juxtaglomerular apparatus (JGA)?

TGF: local in macula densa

JGA: the entire structure, including macular denser, JG cells, mesangial cells

summary:

JG cells

-renin-secreting smooth muscle cells in the afferent arteriole wall acting as intrarenal baroreceptors and endocrine sensors

summary:

angiotensin II

-vasoconstriction

-stimulates aldosterone (inc of Na+ and H20 reabsorption in kidneys)

-stimulates ADH release (water reabsorption in collecting ducts)

-stimulates thirst in hypothalamus

-constriction of efferent arterioles (maintain GFR)