Lecture 4: Posterior Pituitary and HPL Axis Flashcards
What differentiates a preprohormone from a prohormone?
signal peptide
AVP associates with neurophysin ___
II (has 2 names - vasopressin, ADH, goes with NPII)
Oxytocin associates with neurophysin ___
I
Where are the cell bodies for AVP located?
In the PVN (paraventricular) and SON (supraoptic)
What are the 2 types of cells in the PVN?
1) magnocellular
2) parvocellular
Which type of neuron projects into the posterior pituitary?
magnocellular
Where do parvocellular PVN neurons project?
median eminence
regulate mood/anxiety/stress
When is neurophysin cleaved from AVP and oxytocin?
cleaved from prohormone in secretory granules during axonal transport
AVP release increase when plasma osmolarity __________
increases
which comes first, AVP release or thirst sensation?
AVP release
AVP release is tonically inhibited by what?
baroreceptor stretch and firing
decreased stretching during hypotension so you get DISINHIBITION
When plasma osmolarity increases, do osmoreceptors swell or shrink?
SHRINK (inducing AVP release)
GaqPCR stimulates ____
Ca++ (leads to vasoconstriction)
What receptors and where does AVP act?
V2 receptors on the kidney
What does AVP action do in the principal cells of the distal tubule?
phosphorylate aquaporin 2 to move these channels to the apical membrane
SHORT term: quick relocation, not synthesis
LONG term: makes more aquaporin
What are the 2 causes of diabetes insipidus?
1) decreased AVP release
2) decreased renal responsiveness to AVP
(AVP release defect is more common)
What causes diabetes insipidus?
AVP release problem: trauma, infectious disease
Renal responsiveness problem: genetic problem w/ receptor, lithium, hypokalemia
How do you tell the difference between the two causes of diabetes insipidu?
measure AVP levels (if normal, renal problem)
What does oxytocin do?
1) target smooth muscle in breast to stimulate milk ejection
2) stretch the cervix at the end of pregnancy
3) cuddling hormone
What stimulates the production of more oxytocin?
- more suckling
- more contractions
What synthetic hormone is used to stimulate labor?
Pitocin (oxy synthetic)
What is the oxytocin receptor?
GPCRaq