12. Renal Physiology Flashcards
The following are involved in renal autoregulation:
Select true or false for each of the following statements.
A. Adenosine B. Aldosterone C. Bradykinin D. Prostaglandin E2 E. Vasopressin
A. True. Adenosine is an inhibitory influence in renal autoregulation, being produced when hydration/perfusion are good to limit renal blood flow/glomerular filtration
B. False. Aldosterone, bradykinin and vasopressin are not involved in renal autoregulation
C. False. See Feedback B
D. True. PEGE2 dilates the afferent arteriole to maintain renal blood flow when perfusion pressure falls
E. False. See Feedback B
only ADENOSIDE AND PGE2
Adenosine effect on renal auto regulation?
Adenosine is an inhibitory influence in renal autoregulation, being produced when hydration/perfusion are good to limit renal blood flow/glomerular filtration
PGE2 effect on renal auto regulation?
PGE2 dilates the afferent arteriole to maintain renal blood flow when perfusion pressure falls
What do you need to measure GFR?
Clearance of marker
RBF or filtration fraction not needed
How is chloride re-absorbed renally?
Chloride is reabsorbed in the PCT passively down its concentration gradient via the para-cellular route.
How is bicarbonate transported in the kidney?
Actively reabsorbed as CO2
How much glucose is reabsorbed a day?
160 g = 900 mmol
What influence has the autonomic system on the kidneys?
Sympathetic innervation (B1 receptors) of the JGA contributes to renin release
Where in the nephron does ADH act, which receptor and what does it do?
Promotes H2O reabsorption in the COLLECTING DUCT, cell surface receptor GPC.
What is the main objective of the counter current multiplier system?
to generate a hyperosmolar environment in the renal medulla
What is the main energy consuming activity of the nephron?
Sodium reabsorption, at the Na/K ATPase pump.
Whats the main method for glucose reabsorption?
The Na+/glucose symporter is the main method for glucose reabsorption.
Where in the nephron does H+ extrusion occur?
Na+ reabsorption/H+ extrusion occurs in the
PROXIMAL TUBULE
In the Proximal tubule:
1. What percentage of the filtered potassium and water is reabsorbed?
- How much water over all is reabsorbed by the nephron.
in the PT - 2/3 water and potassium filtered is reabsorbed
in the nephron - 99% water reabsorbed.
Is the ascending limb of the loop of henle permeable to water?
Ascending limb is impermeable to water.
An increase in GFR increases the risk of glycosuria: T/F
True.
Glucose delivery to the PCT is determined by the concentration and the GFR. At a concentration of 8 mmol/L and a GFR of 125 mL/min, the delivery rate of glucose is 1 mmol/minute.
What is the tubular transport maximum for glucose?
Tmax for glucose is between 1.5-2.0 mmol/minute
Which of the following have a higher intracellular than extracellular concentration:
Phosphate, Magnesium, Potassium, Calcium, Bicarbonate
Phosphate,
Magnesium,
Potassium
ADH determines whether the majority of water is reabsorbed by the nephron or excreted? T/F
False,
majority of water is reabsorbed at the PCT regardless of ADH.
During renal auto regulation:
- is there contribution directly from sympathetic nervous system?
- Does it involve simultaneous constriction of afferent and efferent arteriole?
- No, only from angiotensin 2
2. No, contributions come from afferent dilatation and efferent constriction.
During renal auto regulation:
Maintains a constant renal artery pressure despite changes in blood flow? T/F
False,
constant flow is maintained despite pressure.
Renal autoregulation:
Increases glomerular filtration fraction in the presence of hypovolaemia. T/F
TRUE
An increase in filtration fraction maintains GFR
Which side of the cell is the main active process of sodium transport occuring?
The main active process is the Na+/K+ pump on the BASAL side of the cell.
How much salt is reabsorbed per day by the kidney?
- 5 kg
99. 5% of it
What is NKCC?
It is the Na-K-Cl cotransporter in the ascending limb, loop of henle that reabsorbs potassium and chloride.
What is the site of action of aldosterone?
Principal cell, DCT
This decides the final sodium excretion.
Whats the normal filtration fraction?
15-20%
In fluid entering the LOH, Fluid is isotonic with plasma?
True - 300 mOsmol/L
Which limb of LOH does Na reabsorption occur?
Thick ascending limb
What percentage of loops in LOH pass deeply into the medulla?
15%
Half life of angiotensin II?
less than 30 seconds.
How is plasma osmolarity affected differently by ADH and aldosterone?
ADH - reduces plasma osmolarity - just H2O reabsorption. Increases urine osmolarity.
Aldosterone - reabsorbs H2O via reabsorbing Na and excreting K, on balance has less determination of osmolarity of plasma or urine.
That is decided by ADH.
