Kidney 3 Flashcards
What dangerous fluctuations does the homeostatic functions of the kidney prevent?
- Fluid levels
- Electrolyte concentration
- pH (Acid-base balance)
What is fluid balance?
The amount of water gained each day equals the amount lost
What is electrolyte balance?
The ion gain each day equals the ion loss
What is acid-base balance?
H+ gain is offset by their loss
What is water excess (overhydration) caused by?
Caused by (a) ingesting large amounts of water; (b) inability to eliminate excess water in urine (e.g. renal or heart failure); (c) hypersecretion of ADH due to endocrine disorders and tumours
What does water excess result in?
Results in hyponatraemia (low blood sodium concentration)
What are the clinical features of water excess?
Progressive clinical features: water intoxication (feeling of drunkenness), confusion, hallucinations, convulsions, coma, death
What is water depletion (dehydration) caused by?
Caused by (a) insufficient intake of water; (b) excessive water loss (e.g. from sweat during exercise) (c) hyposecretion of ADH (diabetes insipidus) or failure of kidneys to respond to ADH (nephrogenic diabetes insipidus)
What does dehydration result in?
Results in hypernatraemia (high blood sodium concentration)
What are the clinical features of dehydration?
Progressive clinical features: severe thirst, dryness and wrinkling of skin, fall in blood pressure, circulatory shock, death
When does Potassium ion excretion by kidney increase?
- ECF concentrations rise
- Aldosterone secreted
- pH rises
When does potassium retention occur?
When the pH falls
What is the pH of the ECF?
Between 7.35 and 7.45
What happens if plasma levels fall below 7.35?
Acidosis
What happens if plasma levels rise above 7.45?
Alkalosis
