Disorders of Vasopressin Flashcards
What part of the pituitary is continuous with the hypothalamus?
Posterior pituitary
What are the 2 key hormones of the posterior pituitary?
AVP
Oxytocin
What neurones contain AVP and oxytocin?
Hypothalamic magnocellular neurones
What is the other name for vasopressin?
Anti diuretic hormone
What is the main physiological action of vasopressin?
Stimulates reabsorption of water in renal collecting duct, concentrating the urine
What are the other 2 minor roles of vasopressin?
Vasoconstrictor via V1 receptor
Stimulates ACTH release
How does vasopressin concentrate urine?
Binds to V2 receptor in collecting duct
Intracellular signalling cascade
Aquaporin 2 channels travel to apical membrane
Water in via aquaporin 2, through cell, through aquaporin 3 on basolateral membrane back into blood
What is the best way to view the pituitary gland?
Pituitary MRI
On an MRI of the pituitary what is the bright spot?
On the posterior pituitary BUT not everyone has it
What are the 2 stimuli for vp release?
Osmotic- rise in plasma osmolality (plasma conc) sensed by osmoreceptors
Non-osmotic- decrease in atrial pressure sensed by atrial pressure receptors
What 2 nuclei are around the 3rd ventricular? What type of receptor do they contain?
Organum vasculosum and subfornical organ, they contain osmoreceptors
What is special about the organum vasculosun and subfornical organ
No blood brain barrier so respond to changes systemic circulation, neurones from here project to the supraoptic nucleus - site of vasopressin release
How is release of vp via osmoreceptors triggered?
Increase in extracellular Na+ Water moves out via osmosis Osmoreceptor shrinks Increased firing AVP release from hypothalamic neurones
Where do atrial strecth receptors detect pressure?
Right atrium
How do atrial stretch receptors work for vp release/inhibition?
When they are stretched and BP is normal/high, they inhibit release via vagal afferents to hypothalamus
If less stretched, less inhibition, more vp release