L08: Renal Blood Supply

Question 1

What is the a vasa recta

Answer 1

The blood supply that wraps around the loop of henle (descending and ascending limb)

Question 2

What is the role of the vasa recta

Answer 2

Take water and solvent from the interstitial space after they have been reabsorbed
Supply substances into the interstitial space which can be secreted

Question 3

What is the mechanism obtained by the vasa recta which allow movement of substances

Answer 3

Counter current mechanism

Question 4

Describe the counter current mechanism of the vasa recta

Answer 4

1) as blood descends to medulla they are exposed to a space with higher osmolality so there is a loss of water as you descend
2) the lost water is reabsorbed by the ascending vasa recta

Question 5

What happens to the flow rate in the descending vasa recta

Answer 5

Decreases

Question 6

What happens to the flow rate in the ascending vasa recta

Answer 6

Increases

Question 7

What regulates the diameter of efferent and afferent arterioles at the glomerulus to stay stable

Answer 7

Autoregulation

Question 8

What is the purpose of the auto-regulation

Answer 8

To maintain blood flow constant and therefore maintain the GFR stable

Question 9

What happens to the afferent arteriole when there is an increase in blood pressure

Answer 9

Vasoconstricts

Question 10

How is the afferent arteriole vasoconstricted

Answer 10

Stretch handles allow sodium to release calcium from the endoplasmic reticulum

Question 11

Therefore what does the auto regulation of afferent arteriole prevent

Answer 11

Increase in blood pressure/blood flow and therefore an increase in GFR

Question 12

What other factors in the body cause vasoconstriction of afferent arterioles in the glomerulus

Answer 12

Sympathetic nerves release noradrenaline that cause vasoconstriction

Question 13

What receptor does noradrenaline act on in the afferent arteriole to cause vasoconstriction

Answer 13

Alpha 1 adrenoceptor

Question 14

What is a method of measuring renal plasma flow

Answer 14

Giving someone p-aminihippurate (PAH)

Question 15

Why is PAH useful to determine blood flow

Answer 15

PAH when given into the blood leaves through the kidney in the urine

Question 16

Therefore by using PAH what can we say

Answer 16

The rate of compound entering kidney/ renal flow= rate of compound leaving the urine

Question 17

What equation can we rearrange to work out renal plasma flow

Answer 17

Renal plasma flow x conc of PAH in plasma (THIS IS WHAT WE GIVE)= urine flow rate x conc in urine

Question 18

What would the rearrangement of the previous equation give

Answer 18

Renal plasma flow= (urine flow rate x PAH in urine)/ conc of PAH in urine

Question 19

Which feedback is in place that controls the blood flow for a single nephron not the whole kidney like autoregulation

Answer 19

The tubuloglomerular reflex

Question 19

Which cell does the tubuloglomerular reflex involve

Answer 19

Macula densa

Question 19

Where is the macula densa located in the nephron

Answer 19

Between the distal tubule and the glomerulus

Question 20

What do macula densa cells detect

Answer 20

Sodium levels

Question 21

Overall what does the tubuloglomerular reflex result in for the afferent arterioles

Answer 21

Vasoconstriction

Question 22

Describe what happens in the tubuloglomerular reflex when there is a high GFR

Answer 22

1) A high GFR mean there is a lot of water and sodium that enters the filtrate
2) a high concentration of sodium is delivered to the straight distal tubule
3) NKCC2 reabsorbed sodium
4) activity of NKCC2 causes the release of ATP from the macula densa
5) ATP is broken into adenosine
6) adenosine causes vasoconstriction of afferent arterioles
7) blood flow decreases and GFR decreases