RENAL- renal blood flow and glomerular filtration

Question 1

what causes the formation of glomerular filtrate

Answer 1

hydrostatic pressure produced by the heart pushes water and solutes through the filtration membrane

Question 2

what is hydrostatic pressure

Answer 2

pressure produced by a fluid against a surface

Question 3

what is capsular hydrostatic pressure

Answer 3

when the fluid in the glomerular capsule creates pressure pushing fluid out of the capsule and back into the glomerulus

opposes glomerular hydrostatic pressure

Question 4

why is the concentration of plasma solutes in the glomerulus higher than plasma concentration in the filtrate

Answer 4

filtration limits the size of particles passing through the membrane

Question 5

what affect does the increased protein concentration in the capsule have

Answer 5

water moves from the capsule back into the glomerulus

Question 6

when does glomerular filtration occur

Answer 6

when glomerular hydrostatic pressure exceeds the hydrostatic pressure of the glomerular capsule and blood colloid osmotic pressure

Question 7

what is blood colloid osmotic pressure

Answer 7

pressure acting to draw water into the glomerulus

Question 8

how do you calculate NFP (net filtration pressure)

Answer 8

NFP = GBHP - (CHP + BCOP)

Question 9

what is the rough value of NFP

Answer 9

10mmHg

55-(15+30) = 10

Question 10

what factors affect GFR

Answer 10

obesity, diabetes, blood urea nitrogen, atherogenic factor, hypertension, meat consumption and smoking

Question 11

how are the kidneys able to autoregulate blood supply in response to systemic blood pressure changes

Answer 11

if there is a drop in blood pressure the afferent artery will relax and the efferent artery will contract

Question 12

outline the Bayliss myogenic response

Answer 12

blood pressure increased in the blood vessels = blood vessel distension = leads to reaction with constriction

stretch of the muscle opens activated ion channels
cells become depolarised resulting in Ca signal triggering muscle contraction - no action potential required
the amount of contraction depends on the amount of stress
increased contraction reduces blood flow

Question 13

outline tubuloglomerular feedback

Answer 13

senses changes in the concentration of sodium chloride in the tubular fluid reaching the macula densa cells in the distal tubule and adjusts the diameter of the afferent arteriole accordingly

increased distal tubular Na concentration causes macula densa cells to swell causing constriction of afferent arterioles so glomerular filtration is decreased

this means that there is more time for Na reabsoprtion as the flow is decreased