Osmoregulation Flashcards
How is osmolarity of ECF adjusted
Adding and removing water NOT solute
To ways to change concentration of a solution
Add / remove water
Add/ remove solute
Where is the site of regulated water loss
Renal tubule
How does adh affect the collecting duct
Makes it impermeable to water , low levels of ADH some water will be reabsorbed d
What level of urine osmolarity signifies the presence of ADH
> 100 mosmol/kg
What’s the main determinant of ECF osmolarity
Plasma sodium concentration
It is the main cation ( 135-145 mmol/L ) in ECF
The contribution of sodium ions to osmolarity is two times the plasma concentration of sodium
Eg if a patients plasma sodium is 160 , their sodium contribution to ECF osmolarity is 320
What is hyponatremia
Too little water
Causes of hyponatremia
Iatrogenic
Excess ingestion
Excess Mineralcortiod activity
Eg primary hyperaldosteronism
Extra renal loss
-dehydration
-infection
Renal losses
-osmostic diuresis
-diabetes insipidus
Diabetes insipidus
- lack of effective ADH
2 types :
Central and nephrogenic
Central: failure of secretion
Nephrogenic :lack of renal response
Symptoms : polydipsia ; abnormally great thirst
Polyuria : abnormally large volume of urine
What does hypoosmotic mean
-lower than normal concentration of solutes in a solution
What does hypernatremia mean
Elevated levels of sodium in the blood , too much sodium relative to the amount of water
What are the signs and causes of SIADH ( syndrome of inappropriate ADH secretion )
Signs - hyponatremia, high urine osmolarity
Causes -CNS damage/ disease
Ectopic ADH production by tumour
What is hypoosmotic hypernatremia
- body loses more water than sodium causes remaining sodium to be more concentrated, can be caused by dehydration
The blood has a lower than normal concentration of solutes but the sodium levels are high
What is hypovolemia
- decreased volume of blood
Causes can be dehydration , haemorrhage
