Water physiology Flashcards
How is the concentration of Na worked out?
How many moles of Na per 1L water
True or False
Water will follow sodium
True
Intracellularly, what is sodium exchanged for?
Hydrogen or potassium
Which steroids have mineralocorticoid activity?
Aldosterone
Cortisol
What happens if there is too little mineralocorticoid activity?
sodium is lost
What happens to water when sodium is lost?
Water is also lost
What hormone controls water loss in the kidney?
Anti-diuretic hormone
Where is ADH released from?
Posterior pituitary
If there is lots of ADH released what does this mean in the urine?
Concentrated urine i.e. water retention
If concentration of sodium is reduced what are the two factors that cause this?
Too little sodium
Too much water
If sodium concentration is increased what causes it?
Too much sodium
Not enough water
What can cause too much water?
SIADH
syndrome of inappropriate ADH
What can cause too little sodium?
Kidney disease e.g. Addisons
Excess sweating
What can cause too little water?
Diabetes insipidus
What can cause too much sodium?
Rare.
High salt feeds in infants
What is Addison’s disease?
Adrenal insufficiency which results in lack of corticosteroids
Why does Addison’s cause sodium loss?
Not enough steroid to regulate to can’t retain Na+ in kidneys so loses Na+ and H2O
Why are Addisons patients hyperpigmented?
Excess ACTH from pituitary
What is an Addisonian crisis?
Severe hypotension leading to coma
Why might potassium be high in Addisons disease?
?
What stimuli can cause too much water?
Hypovolaemia/hypotension
Pain
N&V
How is water retained in SIADH?
ADH is secreted due to a stimuli and this causes water retention
If ADH levels are not high enough what drug can be given?
Desmopressin
What levels of sodium are worrying?
Less than 120
More than 155
