L22 Active Recall: Active Renal Physiology

Question 1

What is the functional unit of the kidney?

Answer 1

Nephron

Question 2

What are the symptoms of severe chronic renal failure?

Answer 2

GFR 10-25 ml/min (severe)
Hypertension ( Fluid accumulation)
Hyperkalaemia (Yes, as normally we secrete excess K+)

Question 3

A patient presents the following symptoms: low plasma phosphate and enhanced urine levels. Identify the protein in the kidney and state where it is found and how it works

Answer 3

Affected NaPII is the protein. Found in the apical membrane of the proximal tubule and it works by using the driving force of the sodium uptake which transported via cotransport.

Question 4

A patient has a gain of function mutation (GOF) in NCC. Identify the impact on early distal tubule sodium handling. List 2 symptoms that patient might display

Answer 4

Increased sodium chloride reabsorption: Increase in blood volume and pressure
Hyperkalemia: Increased sodium reabsorption drives potassium secretion into the tubule via ROMK channel which leads to decrease potassium reabsorption in the collecting duct
Salt retention
Lower urine flow rate: reabsorb more water due to increase in concentration.
Metabolic acidosis

Question 5

You increase 1L of water. Explain what happens to your urine flow rate, and why?

Answer 5

Your urine flow rate would increase, to excrete the excess water

1. Absorbed the water form the small intestine
2. Dilute the plasma - reduce osmolarity
   3, Detected by the hypothalamic osmoreceptors, reduced activity
3. Fewer action potentials in the neurosecretory neurones
4. Less ADH
5. Reduction activation V2 receptor
6. Vesicles containing AQP2 removed from the apical membrane of the principal cells
7. Less AQP2 - more water excretion in the urine

Question 6

Why is amiloride called a potassium sparing diuretic?

Answer 6

Amiloride blocks the ENaCs in the distal convoluted tubule and collecting duct of nephron. Prevents sodium from being reabsorption back into the bloodstream electrical gradient across the tubular cells is is weaker so decreases driving force for potassium secretion into the tubule so less potassium is lost in the urine