bio 252 ch 26 pt 2: the urinary system

filtration + secretion - reabsorption

formula to find excretion rate of any substance

glomerular filtration

good and bad out of blood

tubular reabsorption

reabsorbs good

tubular secretion

rid of extra bad

blood pressure

drives glomerular filtration

20

percentage of plasma that becomes filtrate

48

number of gallons of filtrate produced each day

1-2

quarts of urine produced

fenestration of glomerular endothelial cell

prevents filtration of blood cells but allows all components of blood plasma to pass through

basement membrane of glomerulus

prevents filtration of larger proteins

slit membrane between pedicels

prevents filtration of medium-sized proteins

glomerular blood hydrostatic pressure

GBHP

capsular hydrostatic pressure

CHP

blood colloid osmotic pressure

BCOP

NFP = GHBP - (CHP + BCOP) = 10 mmHg

net filtration pressure (glomerular) formula

GBHP

higher in glomerulus (afferent larger than efferent)

55

GBHP about this number

15

CHP about this number

glomerular filtration rate (GFR)

homeostasis requires a constant…

glomerular filtration rate (GFR)

directly related to net filtration pressure (NFP)

glomerular filtration rate (GFR)

amount of filtrate formed in all renal corpuscles of both kidneys per minute

GFR too low

not cleaning blood; blood becomes toxic

hypertension

due to this, GFR becomes too high

GFR too high

too much filtrate for tubules to handle

GFR too high

tubules not able to reabsorb all good stuff

long-term hypertension

too much pressure on glomerulus and will rupture

80 mmHg

if MAP is less than this, glomeruli will be absorbed

glomerular filtration rate (GFR)

regulated through blood flow and surface area

increase in GFR

increase of blood flow into glomerulus results in…

decrease in GFR

decrease in blood flow into glomerulus results in…

increase in surface area

results in increased filtration and increased GFR

decrease in surface area

results in decreased filtration and decreased GFR

myogenic mechanism

responds directly to changes in blood pressure

renal auto regulation

maintains GFR despite changes in mean arterial pressure

myogenic mechanism

responds directly to changes in BP

tubuloglomerular feedback

regulate GFR is reabsorption is off

myogenic mechanism

acts more quickly than other form of renal auto regulation

autonomic nervous system

neural regulation of GFR done by the…

sympathetic signals

glomerulus only receives this kind of regulation of GFR

auto regulation

if SNS signals are low, this will dominate

angiotensin II

vasoconstrictor that decreases blood presure and GFR

atrial natriuretic peptide

relax mesangial cells within glomerulus

atrial natriuretic peptide

increases surface area; increases GFR

myogenic mechanism

stretched smooth muscle fibers contract, thereby narrowing lumen of afferent glomerular arterioles

myogenic mechanism

increased stretching of smooth fibers in afferent glomerular arteriole walls due to increased blood pressure

tubuloglomerular feedback

rapid delivery of Na+ and Cl- to the macula densa due to high systemic blood pressure

tubuloglomerular feedback

decreased release of nitric oxide by juxtaglomerular apparatus causes constriction of afferent glomerular arterioles

neural regulation

increase in activity level of renal sympathetic nerves releases norepinephrine

neural regulation

constriction of afferent glomerular arterioles through activation of a1 receptors and increased release of renin

angiotensin II

constriction of afferent and efferent glomerular arterioles

angiotensin II

decreased blood volume or blood pressure stimulates production of this

atrial natriuretic peptide

dilating afferent arterioles; constricting efferent arterioles

atrial natriuretic peptide

prevents sodium reabsorption; increases water excretion

angiotensin II

regulates blood pressure by constricting both afferent and efferent arterioles; increases renal blood flow and increases GFR

angiotensin II

stimulates cortex to release aldosterone; vasopressin release

norepinephrine

decrease GFR; decrease urine output

tubuloglomerular feedback

less than 80 BP; cannot compensate for extreme hypotension (shock)

tubuloglomerular feedack

adjust diameter of afferent arteriole based on NaCl concentration in filtrate

GFR too high

macula densa cells vasoconstrict afferent arteriole

GFR too low

macula densa cells vasodilate afferent arteriole by releasing nitric oxide and stimulate juxtaglomerular cells to release renin

myogenic mechanism

vasodilation of afferent arteriole helps maintain sufficient pressure inside glomerulus

myogenic mechanism

vasoconstrict in response to stretch of afferent arteriole to reduce blood flow to glomerulus to prevent rise in GHP

increase in GFR, increase in NFP

high BP; dilation of afferent arteriole

decrease in GFR; decrease in NFP

low BP, constriction of afferent arteriole, dehydration

GFR and NP = 0

severe hypotension, glomerular damage, kidney failure

blood colloid osmotic pressure

about 30 mmHg

blood colloid osmotic pressure

pulling water back into capillaries due to plasma proteins in blood

capsular hydrostatic pressure

pushing fluid back into glomerular capillaries due to filtrate in bowman’s capsule

glomerular blood hydrostatic pressure

pushes fluid out of glomerulus into bowman’s capsule; generated by blood pressure in glomerular capillaries

tubular secretion

renal tubules actively transport substances from blood into filtrate