L08: Renal Blood Supply Flashcards
What is the a vasa recta
The blood supply that wraps around the loop of henle (descending and ascending limb)
What is the role of the vasa recta
Take water and solvent from the interstitial space after they have been reabsorbed
Supply substances into the interstitial space which can be secreted
What is the mechanism obtained by the vasa recta which allow movement of substances
Counter current mechanism
Describe the counter current mechanism of the vasa recta
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
What happens to the flow rate in the descending vasa recta
Decreases
What happens to the flow rate in the ascending vasa recta
Increases
What regulates the diameter of efferent and afferent arterioles at the glomerulus to stay stable
Autoregulation
What is the purpose of the auto-regulation
To maintain blood flow constant and therefore maintain the GFR stable
What happens to the afferent arteriole when there is an increase in blood pressure
Vasoconstricts
How is the afferent arteriole vasoconstricted
Stretch handles allow sodium to release calcium from the endoplasmic reticulum
Therefore what does the auto regulation of afferent arteriole prevent
Increase in blood pressure/blood flow and therefore an increase in GFR
What other factors in the body cause vasoconstriction of afferent arterioles in the glomerulus
Sympathetic nerves release noradrenaline that cause vasoconstriction
What receptor does noradrenaline act on in the afferent arteriole to cause vasoconstriction
Alpha 1 adrenoceptor
What is a method of measuring renal plasma flow
Giving someone p-aminihippurate (PAH)
Why is PAH useful to determine blood flow
PAH when given into the blood leaves through the kidney in the urine
Therefore by using PAH what can we say
The rate of compound entering kidney/ renal flow= rate of compound leaving the urine
What equation can we rearrange to work out renal plasma flow
Renal plasma flow x conc of PAH in plasma (THIS IS WHAT WE GIVE)= urine flow rate x conc in urine
What would the rearrangement of the previous equation give
Renal plasma flow= (urine flow rate x PAH in urine)/ conc of PAH in urine
Which feedback is in place that controls the blood flow for a single nephron not the whole kidney like autoregulation
The tubuloglomerular reflex
Which cell does the tubuloglomerular reflex involve
Macula densa
Where is the macula densa located in the nephron
Between the distal tubule and the glomerulus
What do macula densa cells detect
Sodium levels
Overall what does the tubuloglomerular reflex result in for the afferent arterioles
Vasoconstriction
Describe what happens in the tubuloglomerular reflex when there is a high GFR
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
