Renal II: Glomerular Filtration Flashcards
filtration
blood plasma filtered into capsular space
reabsorption
water and useful substances are reabsorbed into blood from tubular fluid
secretion
certain wastes are removed from blood by secretion into tubular fluid (soon to be urine)
excretion
the process of eliminating waste products from the body
rate of excretion
rate of glomerular filtration + rate of secretion - rate of reabsorption
what are the three layers of the filtration barrier of glomerular filtration?
fenestrated endothelium, basement membrane, podocytes
What does the fenestrated endothelium of the glomerular capsule filter and allow to pass through?
filters blood cells, allows components of blood plasma to pass through
What does the basement membrane of the glomerular capsule filter?
large proteins, negatively charged substances
What do the podocytes of the glomerular capsule filter?
medium sized proteins
NFP =
GBHP - CHP - BCOP
what does GBHP do
forces blood into glomerulus
What is GFR?
glomerular filtration rate
Amount of filtrate formed in all renal corpuscles of both kidneys per minute
What happens if GFR is too high?
Useful substances are lot due to the blood passing through too quickly
(everything goes through)
What happens if GFR is too low?
Sufficient waste products may not be removed
Why is a constant GFR required to maintain homeostasis?
to ensure everything that needs reabsorbed gets reabsorbed (maintain homeostasis of blood, BP, blood volume)
What does NFP depend most heavily on?
GBHP
At what level does GBHP stop filtration?
less than 45 mmHg
(MAP 80-100 mmHg does NOT stop filtration)
What are the 3 mechanisms for GFR regulation?
auto
neural
hormonal
What cells are at the top of the ascending limb of the loop of Henle?
Macula densa cells
What cells line the afferent arteriole?
juxtaglomerular cells
What are mesangial cells?
contractile cells associated with the capillaries
What two mechanisms play a role in autoregulation of GFR?
myogenic mechanism and tubuloglomerular feedback
Which mechanism of autoregulation of GFR is faster?
myogenic mechanism
What causes the myogenic mechanism of autoregulation of GFR?
systemic increases in blood pressure stretching the afferent arteriole
What is the effect of the myogenic autoregulation of GFR?
smooth muscle contraction reduces the diameter of the afferent arteriole which returns the GFR to its previous levels in seconds
What causes the tubuloglomerular feedback of autoregulation of GFR?
elevated systemic BP raises the GFR so that fluid flows too rapidly through renal tubule
Na+, Cl-, and water are not reabsorbed so there is an increase in them
What cells detect the increased levels of Na+ and Cl- causing the tubuloglomerular feedback of autoregulation of GFR?
macula densa cells in the ascending limb of the loop of henle
What are the effects of tubuloglomerular feedback of autoregulation of GFR?
inhibits release of NO (a vasodilator) from juxtaglomerular apparatus
afferent arterioles constrict, reducing GFR
Does neural regulation lower or raise GFR?
lower
What happens during neural regulation of GFR?
Blood vessels of the kidney have sympathetic fibers that cause vasoconstriction of afferent arterioles caused by norepinephrine release
What neurotransmitter is used for vasoconstriction of afferent arterioles in neural regulation of GFR?
norepinephrine
Does autoregulation or neural regulation of GFR take precedent?
neural regulation overrides renal autoregulation
What arterioles undergo vasoconstriction with moderate sympathetic stimulation during neural regulation of GFR?
both afferent and efferent arterioles
When does extreme sympathetic stimulation occur?
During exercise or hemorrhage
What occurs when extreme sympathetic stimulation for neural regulation of GFR happens?
vasoconstriction of afferent arterioles
GFR decreases substantially
lowers urine output to maintain blood volume
permits greater blood flow to other tissues (muscle)
What two hormones contribute to the regulation of GFR?
Atrial Natriuretic Peptide (ANP) and Angiotensin II
What effect does atrial natriuretic peptide have on GFR?
ANP increases GFR
What triggers the hormonal regulation release of atrial natriuretic peptide?
High blood volume causes atrial stretching releasing ANP from the heart
How does atrial natriuretic peptide increase GFR?
ANP relaxes glomerular mesangial cells, increasing glomerular capillary surface area and increasing GFR
Does angiotensin II increase or reduce GFR?
reduce GFR
