Control of the Glomerular Filtration Rate

unit 4 week 12 lesson 5

what are the two internal mechanisms that our body use to maintain GFR even if bp fluctuates and what do they do

• they function to protect the kidney from damage

• if bp spikes too high, it could potentially damage tle blood vessels in the kidney

• therefore we have autoregulatory mechanisms that will be triggered to maintain blood pressure within the glomerulus of each nephron

1. Myogenic Response

2. Tubuloglomerular Feedback

myogenic response/theory in kidney

• when blood flow increases in each nephron, this will increase pressure within each glomerulus and increase the GFR

• the myogenic respones will reduce the GFR to keep it constant

• the response is a reflexive contraction of the afferent arteriole

• blood flow into each glomerulus will be reduced, bringing the GFR back down

Tubuloglomerular Feedback

• the macula densa (cells found in junction of ascending loop of Henle that passes thru the afferent and efferent arteriole) detect salt composition of the filtrate and rate of fluid flow)

• if bp increases, this will cause an increase in how much fluid is filtered.

• that will increase the amount of solute (na,cl) being filtered

• when na and cl levels are too high, or when fluid flow is too high, the macula densa cells release a paracrine factor (adenosine) that stimulates the afferent arteriole to constrict and reduce the rate of fluid filtration.

what happens when both afferent and efferent arterioles experience vasoconstriction (from angiotensin ||)

• decrease in GFR

• When so little blood has been permitted to enter the glomerulus, even though the efferent arteriole is also vasoconstricted, the overall outcome is less fluid filtration.