Regulation of osmolarity Flashcards
(30 cards)
Where is ADH synthesised?
Magnocellular neurons in the hypothalamus
Where is ADH secreted?
Posterior pituitary
When osmoreceptors detect an increase in the OP, what happens to ADH secretion?
Increased ADH production
What happens to ADH secretion when osmolarity decreases?
Decreased
What is the difference between osmolarity & tonicity
Molecules which can penetrate the membrane along with water do not produce tonicity but affect osmolarity.
Impermeable molecules affect tonicity
What is urea?
Ineffective osmole
Does urea change the osmolarity?
Yes
What increases the permeability of collecting ducts to water? How?
ADH
Aquaporins
If maximal ADH is produced, how concentrated will the urine become?
1200mOsm
With maximal ADH, what urine will be produced?
Small concentrated urine
In the absence of ADH, what is the concentration of urine?
100mOsm
30-50 due to more ion reabsorption
Is the CD permeable or impermeable to water in the absence of ADH?
Impermeable
Are CD permeable to urea?
Yes
What enhances the CD permeability to urea?
ADH
In antidiuresis, what will happen to urea levels? What does it do
Reabsorb urea
Acts to reinforce the medullary interstitial gradient
Why is it important that urea can be recycled during antiduiresis?
It has an osmotic effect therefore would draw water into CD
When ECF increases, what happens to ADH secretion?
Decreases
When ECF decreases, what happens to ADH secretion?
Increases
Where are low P receptors found?
R & L atria & great veins
Where are the High P receptors found?
Carotid & aortic arch baroreceptors
What normally tonically inhibits ADH secretion?
Vagus nerve
What affect does orthostatic hypotension have on ADH secretion?
Increases ADH
What stimulates increase in ADH production?
Exercise Stress Nicotine Pain Emotion
What decreases ADH secretion?
Alcohol
