Urinary: Ion Regulation Flashcards
Describe the pH of the filtrate as it flows through the tubules?
- 7.4 when filtered
- 6.7 at the end of the PCT
- 4.5 - 8 at the collecting duct
What is the minimum urine pH?
4.5
What are the buffers of the urine that helps to control the H+ (pH) ?
(HPO4)2-
NH4+
Excess H+ removed by ammonia system as phosphate is only secreted at 25-30 mmol/d
What is the difference in acid-base status between vomitig and diarrhoea?
Vomiting
- Loss of H+
- Loss of K+
- Result in metabolic alkalosis
Diarhoea
- Loss of K+
- Loss of bicarbonate
- Results in metabolic acidosis
What are the side effects of furosemide?
- Contirbutes to chloride loss
- Also contribute to potassium, salt and water loss
What is the distribution of potassium in the body?
-Mostly intracellular
How does the body prevent excess potassium in the ECf?
- Quick K+ uptake into cells
- K+ excretion in urine
What increases 3Na+/2K+ ATPase activity?
- K+ concentration in plasma
- Insulin
- Noradrenaline effect on B2 arenoreceptors
What increases potassium movement out of the cell?
- High osmolality
- Acidosis
- Cell damage
- Exercise
What reduces potassium moving out of the cell?
Alkalosis
What increase potassium movement into the cell? 3Na+/2K+
- ECF (K+)
- Insulin
- B2 receptor agonists
- NA/Salbutamol
- Aldosterone
What inhibits potassium movement into cells?
- Digitalis
- Chronic disease
How is potassium excreted?
Under normal circumstance
- Small amounts of potassium are lost in faeces and sweat
- Kidney predominantly responsible for excretion in urine. 15 mmol/day
- Potassium is regulated by excretion not absorption
How is variable potassium excretion controlled?
- If plasma potassium concentration is low, less excretion in DCT and CD
- If plasma potassium concentration is high, more excretion occurs in DCT and CD
What causes increases potassium secretion?
- Increased intracellular K+
- Electronegative lumen
- Permeability of luminal membrane
- Decreased luminal K+
