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Renal Physiology

Terms in this set (70)

kidney main function
maintain O2 balance in body
nephron 2 components
1. vascular
2. tubular
Vascular component (4)
1. afferent arteriole
2. glomerulus
3. efferent arteriole
4. peritubular capillaries
afferent arteriole carries blood
TO the glomerulus
glomerulus is a tuft of
capillaries that filters proten-free plasma into the tubular component
efferent arteriole carries blood
from the glomerulus
peritubular capillaries supply the
renal tissues
peritubular capillaries involved in
exchanges with the fluid in the tubular lumen

exchange between tubular fluid and plasma
filtered blood from the glomerulus travels to the
tubule to be excreted as urine
dominant part of the vascular component of the nephron
glomerulus
nephron vascular component pathways (4)
1. from renal artery blood -> AFFERENT arterioles to the glomerulus
2. EFFERENT arterioles transport blood FROM the glomerulus
3. efferent arterioles branch out to become PERITUBULAR CAPILLARIES which surround the tubular part of the nephron
4. peritubular capillaries join into VENULES which transport blood into renal vein
glomerular filtration
nondiscriminant filtration of a protein-free plasma from the glomerulus into Bowman's capsule
tubular reabsorption
selective movement of filtered substances from the tubular lumen BACK into blood of the peritubular capillaries
tubular secretion
selective movement of nonfilterd substances from the peritubular capillaries into the tubular lumen
tubular secretion provides
second route after filtration for substances to enter renal tubules from blood
___- % of the plasma that enters glomerulus is filtered
20
anything filtered or secreted but not reabsorbed is
excreted in urine and lost from the body
anything filtered and reabsorbed enters
venous system and is saved for the body
glomerular filtrate is produced when
plasma is passively forced through the glomerular membrane into Bowmans capsule
the layers of the glomerular membrane keep _____ in blood and _____ in filtrate
blood cells and plasma proteins; H2O and solutes
Forces involved in glomerular filtration (3)
1. glomerular capillary blood pressure (MAJOR)
2. plasma-colloid osmotic pressure
3. Bowman's capsule hydrostatic pressure
forces that oppose filtration (2)
1. plasma colloid osmotic pressure
2. bowman's capsule hydrostatic pressure


-if these pressures increase filtration will decrease
forces that favor filtration (2)
1. glomerular capillar BP
2. net filtration pressure
glomerular capillary BP is the
fluid pressure exerted by blood within glomerular capillaries
glomerular capillary BP depends on (2)
1. contraction of the heart
2. resistance to blood flow from efferent and afferent arterioles
higher cardiac output results in
higher glomerular filtration
the effect of exercise on glomerular filtration
vasocontricts blood flow to the viscera = decreased filtration
plasma colloid osmotic pressure caused by
unequal distribution of plasma proteins across glomerular membrane
Bowman's capsule hydrostatic pressure
pressure exerted by fluid in initial part of tubule
-pushes fluid out of Bowman's capsule
GFR =
glomerular filtration rate
GFR depends on (3)
1. net filtration pressure
2. glomerular surface area
3. permeability
two major control mechanics of glomerular capillar BP on GFR (2)
1. autoregulation
2. extrinsic sympathetic control
autoregulation
prevents spontaneous changes by changing RADIUS of afferent arteriole
= myogenic mechanism
myogenic mechanism
arteriole smooth muscle response to stretch = constriction
-controls flow in response to pressure change
extrinsic sympathetic control
long-term regulation of arterial BP
-SNS input to afferent arterioles
NO _____ control of kidney
parasympathetic
granular cells secrete
renin
renin secreted due to
drop in BP
vasoconstriction ______ GFR
decreases

-decrease glomerular capillary BP
-decrease net filtration pressure
vasodilation ______ GFR
increases

-increases glomerular capillary BP
-increases net filtration pressure
increases sympathetic activity will _____ GFR
decrease
tubular reabsorption involves
transepithelial transport
Reabsorbed substances must cross 5 barriers (5)
1. must leave tubular fluid by crossing LUMINAL MEMBRANE of tubular cell
2. must pass thru CYTOSOL from one side of tubular cell
3. must cross BASOLATERAL MEMBRANE of tubular cell to enter ISF
4. diffuse through ISF
5. penetrate CAPILLARY WALL to enter blood plasma
tubular reabsorption (passive)
no energy required for net movement
-movement occurs DOWN electrochemical or osmotic gradients
Most Na+ reabsorption occurs early in
nephron and is unregulated
_____ pump in basolateral membrane is essential for _____
Na+-K ATPase; Na+ reabsorption
Na+ is pumped _____ gradient and water _____ gradient
against
diffuses down
the basolateral Na+K- pump actively transports
Na+ from the tubular cell into the ISF

-establishes a pssive movemebt of Na+ from lumen into the tubular cell and from ISF to peritubular capillary
Kidneys secrete renin when (3)
1. ECF volume decreases
2. plasma volume decreases
3. BP decreases
renin stimulates _____ secretion from the _____
aldosterone; suprarenal glands
aldosterone increases
Na+ reabsoprtion from the distal portions of tubule
RAAS pathway
1. decrease in BP
2. renin release from kidney
3. angiotensinogen in blood converted to AGI
4. ACE from the lungs converts AGI to AGII
3. AGII stimulates adrenal gland to release aldosterone
4. aldosterone stimulates kidney to reabsorb Na+
5. H2O retained
=Increase in BP
AGII results in (4)
1. Vasopressin being released
2. increased thirst
3. arteriolar vasoconstriction
4. aldosterone release from adrenal cortex
_____ of water reabsorbed is uncontrolled
80%
-chasing Na+ down gradient passively
controlled water reabsorption due to
Vasopressin (ADH)
role of vasopression (ADH)
increase permeability of tubule to H2O by promoting insertion of aquaporins in the luminal membrane
vasopressin produced in the ____ and stored in the ______
hypothalamus; posterior pituitary
during water deficit vasopressin secretion ____
increases
during excess water vasopressin secretion _____
decreases
-less water absorbed = more water excreted
mechanism of vasopressin (5)
1. VP binds with its receptor on basolateral wall
2. binding stimulates cAMP
3. cAMP increases luminal membrane's permeability H2O by promoting insertion of water channels
4. H2O enters tubular cells from the tubular lumen through inserted channels
5. water exits cell and enters blood
urea is a product from
protein degradation
____% of filtered urea is _____ reabsorbed in the proximal tubule
50; passively
secretory systems are for (2)
1. H+
2. K+
H+ important for
regulating acid based balance
K+ under control of
aldosterone
the basolateral pump simutaneously transports ____ into the lateral space and ____ into the tubular space
Na+; K+
low aldosterone = ____ BP = ____K+
low BP
high K+
high aldosterone = ____BP = ____K+
high BP
low K+
stimulated stretch receptors signal
smooth muscle in the bladder wall by PNS neurons
PNS stimulation = bladder
contraction
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