Regulation of GFR, Reabsorption and Secretion

all of the mechanisms for renal auto regulation of GFR

work together

in the myogenic mechanism smooth muscle in

the walls of the afferent arterioles is sensitive to blood pressure

in the myogenic mechanism, as blood pressure increases

the smooth muscle constricts to decrease GFR (triggered by the stretching of the blood vessels)

in the myogenic mechanism, as blood pressure decreases

the smooth muscle dilates (relaxes) to increase GFR

the myogenic mechanism helps to

maintain a constant GFR, despite changes in systemic blood pressure

if systemic blood pressure increase, GFR would also increase if not for

tubuloglomerular feedback

as GFR begins to increase

there is less time for reabsorption

when GFR increases what happens to Na+ and Cl-

more Na+ and Cl- remain in the filtrate

when GFR increases what happens to H2O

more H20 remains in filtrate

macula densa cells are located in

the ascending LOH

macula densa cells detect

increase in Na+, Cl- and H2O within the filtrate

in response to detecting increase in Na+, Cl- and H2O within the filtrate, macula densa cells

inhibit the release of nitric oxide (NO)

a lack of NO leads to

vasoconstriction

vasoconstriction in terms of tubuloglomerular feedback

limits the amount of blood that can enter the glomerulus and effectively regulating GFR

the sympathetic division of the ANS stimulates

smooth muscle of the afferent srterioles

SNS releases

NE

NE causes

vasoconstriction of afferent arteriole

vasoconstriction of afferent arteriole

limits blood flow to the golmerulus

effect of diuretics like coffee

causes vasodilation of the afferent arteriole causing more blood flow to glomerulus

angiotensin II causes

vasoconstriction of afferent arteriole

atrial naturetic peptide (ANP)

increases GFR

atrial naturetic peptide (ANP) is secreted from

the atria of the heart

atrial naturetic peptide (ANP) is secreted in response to

stretching of the atria due to high BP or high blood volume

atrial naturetic peptide (ANP) causes

relaxation of mesangial cells (which affects blood cells)

mesangial cells are

contractile cells within the glomerulus (cord example)

what is the effect of mesangial cells being relaxed in the glomerulus

increase glomerular capillary surface are -> increases GFR -> increases urine output

all mechanisms for GFR regulation act to decrease GFR except

ANP

angiotensin II is secreted in response to

low BP, low Na+ and low volume

angitensin II triggers

vasoconstriction and secretion of aldosterone

aldosterone is secreted by

the adrenal cortex

aldosterone promotes

reabsorption of Na+ from the DCT and CD (H2O follows)

ADH is secreted by the

posterior pituitary

ADH is secreted in response to

dehydration

alcohol prohibits

the release of ADH (why you pee a lot when you drink)

ADH increases

water permeability in the DCT and CD

ADH stimulates

principle cells to insert aquaporin-2 into apical membrane

aquaporin-2 is

a water channel

ADH allows water to be

reabsorbed from the filtrate

what is the opposite of ADH

aldosterone

ANP inhibits

Na+ reabsorption in the PCT, DCT and CD

if NA+ reabsorption is inhibited then

reabsorption of water is also inhibited meaning H2O stays in filtrate and is excreted in the urine

the mechanism of ANP secretion is ____ feedback

negative