1b Disorders of Vasopressin Flashcards
What is the physiological action of vasopressin?
Stimulation of water reabsorption into the renal collecting duct = concentrates the urine
what are the 2 posterior pituitary hypothalamic nuclei called and for which hormone? What are the neurons called?
magnocellular nuerons from supraOptic and paraVentricular nuclei
What are the two enantiomers named as and which is biodegrable?
L & D and L is
Which receptor does AVP work through?
V2 receptor in the kidney
How does AVP work as a vasoconstrictor?
Via the V1 receptor
Describe how AVP concentrates the urine?
- AVP binds to V2 receptor on basolateral membrane
- This triggers intracellular cascade (g protein etc) resulting in the movement of aquaporin-2 molecules onto the apical membrane
- this allows the movement of water from the urine into the blood, therefore concentrating it
What is the physiological action of vasopressin aka ADH? (3)
- Stimulation of water reabsorption- acts through V2 receptor in the kidney
- Also a vasoconstrictor via V1 receptor
- Stimulates ACTH release from anterior pituitary
What is the bright spot on an MRI of the pituitary?
Posterior Pituitary
What are the two stimuli for vasopressin release?
Osmotic and Non-osmotic
Describe how the osmotic stimuli for vasopressin release works?
rise in plasma osmolality (conc) detected by osmoreceptors. Water moves out via osmosis and change in shape causes nuerone firing - AVP release
Describe how the non-osmotic stimuli for vasopressin works?
decrease in atrial pressure sensed by atrial stretch receptors STOP INHIBITION of AVP so this: - increases pressure through V1 vasoconstriction - increase plasma volume through V2 - increase ACTH from pit
Describe how osmoreceptors regulate vasopressin?
- Increase in extracellular sodium
- Therefore movement of water out the osmoreceptor by diffusion
- Osmoreceptor shrinks
- This increases osmoreceptor firing
- More osmoreceptor firing leads to more AVP release from the hypothalamic neurones
Describe how the non-osmotic stimulation of Vasopressin works?
- stretch receptors in atrium detect pressure and INHIBIT RELEASE
- Therefore when the volume drops, the stretch receptors are stretched less, so LESS INHIBITION OF VASOPRESSIN
What might trigger the non-osmotic stimulation of Vasopressin Release?
Major haemorrhage
What are the benefits of vasopressin release following major haemorrhage?
- Increase the circulating volume
- Restore the blood pressure which will have dropped
How doe AVP trigger an increase in blood volume following haemorrhage?
Increased water absorption in the kidney via V2 receptor, therefore increasing blood volume and hence pressure as well
Which receptors does AVP initiate vasoconstriction through?
V1 receptors
What is the physiological response to water deprivation?
- Increased plasma concentration
- This stimulates the osmoreceptors to fire, leading to AVP release
- This stimulates water reabsorption from the renal collecting ducts
- Urine volume decreases, and the concentration of the urine increases as more water is kept
- This reduces the plasma concentration