Quiz 7 Flashcards
What fraction of electrolytes and other substances are reabsorbed in the PCT?
2/3
What is the difference between the thin and thick parts of the loop of Henle?
thin- very permeable to water
thick- not very permeable, needs pumps
What does the adrenal medulla secrete?
catecholamines
What does the zona reticularis secrete?
androgens- think sex hormones
What does the zona fasciculata secrete?
glucocorticoids- think sugars
What does the zona glomerulosa secrete?
aldosterone- think salt
Where does the “fine tuning” occur in the nephron?
distal tubule and collecting duct
What happens to urine in hyperglycemia?
pumps are overwhelmed- glucose excreted in urine (not normal)
What % of CO do the kidneys receive?
20-25%
Afferent vs efferent arteriole
afferent- into glomerulus
efferent- out of glomerulus
What happens in the PCT?
reabsorption of nutrients
What happens in the nephron loop?
establishes osmotic gradient- promotes water reabsorption
What happens in the DCT?
makes further adjustments in composition of tubular fluid- combination of secretion and reabsorption
What happens in the collecting duct?
receives urine and performs final adjustments of volume and composition- carries tubular fluid through osmotic gradient in renal medulla
What substances filter into the Bowman’s capsule?
water and low molecular weight substances
renal blood flow is directly proportional to:
pressure difference between renal artery and renal vein
Renal blood flow is indirectly proportional to:
resistance of renal vasculature
Difference between cortex and medulla
cortex- receives 90-95% of BF- contains pumps
medulla- flow is restricted by vascular resistance- slow for concentrating urine
What causes the glomerular capillaries to be a high pressure system?
resistance of efferent arteriole
What leads to decrease in RBF?
vasoconstriction of renal arterioles (SNS activation, angiotensin II)
What leads to increase in RBF?
vasodilation of renal arterioles (prostaglandins, bradykinin, NO, dopamine)
What are the 2 mechanisms for autoregulation of RBF?
myogenic mechanism and tubuloglomerular feedback
Myogenic mechanism
renal afferent arterioles contract in response to stretch- increased renal arterial pressure stretches arterioles, which contract and increase resistance to maintain constant RBF
Tubuloglomerular feedback
increased renal arterial pressure leads to increased delivery of fluid to macula densa- which senses increased load and causes constriction of nearby afferent arteriole, increasing resistance to maintain BF
What do juxtaglomerular cells do?
release renin into circulation in response to decreased RBF from hypovolemia, hypotension, renal ischemia, or SNS stim
Filtration pressure=
MAP - (colloidal oncotic P + glomerular filtrate P)
should always be + in normal physiology
Effects of constriction of afferent arteriole
Decreased GFR
Decreased renal plasma flow
no change in filtration fraction
Effects of constriction of efferent arteriole
increased GFR
decreased renal plasma flow
increased filtration fraction
Effects of increased plasma proteins
decreased GFR
no change in renal plasma flow
decreased filtration fraction
Effects of ureteral stone
decreased GFR
no change in renal plasma flow
decreased filtration fraction
Effects of anesthesia on RBF
redistributes blood flow away from cortex (vasodilation)- causes sodium and water conservation (less u.o.)
decreases in BF causes release of AVP (vasopressin)
Does intraop u.o. correlate with postop changes in renal function?
no
