Nephro Physiology Flashcards
anatomy of nephron in order
proximal tubule
loop of henle with capillary network (down thin descending, up thick ascending)
distal tubule
collecting duct
start of filtration of nephron
glomerulus surrounded by bowmans capsule
early/proximal convoluted tubule (PCT)
- brush border that reabsorbs ALL glucose and AA (from urine > lumen > blood)
- reabsorbs most bicarb, sodium, chloride, potassium, water, uric acid, and phosphorus
parathyroid hormone - inhibits sodium/phosphorus cotransport (reabsorption)
what enzyme is used in PCT resorption processes
carbonic anhydrase
thin descending loop of henle
-passive reabsorption of water
-impermeable to sodium
-makes urine hypertonic (concentrated)
functions of parts of the nephron
- renal corpuscle: filtration
- PCT: reabsorption, secretion (vital)
- Loop of henle: solution concentration
- DCT: reabsorption, secretion (optional)
- collecting duct: (optional)
where is the only area of the nephron that cannot reabsorb sodium?
thin descending loop of henle
thick ascending loop of henle
- reabsorbs smaller amounts of sodium, potassium, and chloride (requires ATP)
- indirectly absorbs magnesium/calcium paracellularly (bw cells) via gradient generated by potassium backleak
- impermeable to water
- urine less concentrated
distal convoluted tubule
-reabsorbs even less sodium
-reabsorbs chloride
-impermeable to water
-makes urine fully dilute (hypotonic)
PTH inc ca reabsorption via ca/na exchange
collecting duct
- reabsorbs small amounts of sodium in exchange for potassium/hydrogen (regulated by aldosterone)
ADH inserts more aquaporin water channels on apical side of membrane (urine side) and inc urea reabsorption
what section of the nephron is trying to absorb everything?
PCT
only gets rid of Hydrogen
concerning the RAA system, what do the kidneys produce vs the liver?
liver: angiotensinogen
kidneys: renin
what converts angiotensinogen to angiotensin I?
renin from the kidney
what converts angiotensin I to angiotensin II
ACE from the surface of the pulmonary and renal epithelium
what stimulates the kidneys to produce renin?
decrease in renal perfusion (JGA)
what are the effects of angiotensin II?
-inc symp activity
-stim tubular na/cl reabsorption, k excretion, h2o retention
-arteriolar vasoconstriction, inc BP
-stim ADH secretion via post pituitary
- stim h20 reabsorption in collecting duct
- inc aldosterone secretion via adrenal cortex (inc BV via inc na and h20)
overall water and salt retention, effective circulating volume inc. perfusion of JGA inc.
RAA system regulation
neg feedback via JGA pressure measurements
renin secretion and effects
- secreted by JG cells
- inc secretion due to dec renal perfusion pressure (low blood vol, detected by afferent arteriole)
- inc renal sympathetic d/t (B1 effect)
- dec NaCl delivery to macula densa cells (bc its reabsorbing it back into the blood)
what things could be triggers for the RAA system?
dehydration
Na def
hemorrhage
high EC pot (affects at aldosterone stage, not full sys)
ACE secretion and effects
- catalyzes conversion of angiotensin I > II
- located in multiple tissues
- conversion occurs the most in the lung
- provided by vascular endothelial cells in the lung
angiotension II functions
- maintains BP and volume
- affects baroreceptors
- limits reflex bradycardia (HR dropping with blood vol change)
atrial/brain natriuretic peptide (ANP/BNP) secretion and functions
- released from atria and ventricles
- released due to inc volume to inhibit RAA system
- relaxes vascular smooth muscle via cGMP > inc GFR, dec renin
- dilates afferent arteriole
ADH/vasopressin effect on nephro sys
- regulates serum osmlolality
- responds to low blood vol states
- stim reabsorption of water in collecting ducts
- stim reabsorption of urea in collecting ducts
aldosterone effect on nephro
- reg EC fluid vol and sodium content
- inc release in hypovolemic states
- inc potassim excretion in response to hyperkalemia (exchanging it for sodium)
