Lecture 29-The Posterior Pituitary Flashcards
How does vasotocin function in animals?
- mating
- childrearing
What are the similarities between the pre-propeptides of AVP and oxytocin?
AVP: 1 peptide, AVP, Neurophysin II, glycosylation
oxytocin: 1 peptide, oxytocin, Neurophysin I
Describe the AVP V1a Rs.
- Gq PLC Stimulation Liver, smooth muscle, CNS, vasoconstriction
- Gi AC inhibitory Liver
Describe the AVP V1b R
Gq PLC stimulatory On corticotrophs of anterior pituitary-stimulate ACTH release
Describe the AVP V2 R
Gs AC stimulatory Distal collecting tubules of kidney, salt and water balance
Describe the oxytocin R
Gq PLC stimulatory smooth muscle contraction, uterus, mammary glands, CNS
Where do magnocellular neurons receive input to regulate output of hormone?
very sensitive osmoreceptors in the anterior hypothalamaus, non-osmoreceptors (eg. baroreceptors) into the ascending brainstem.
- drug and hormone effects affect both baroreceptor and osmoreceptor activity as well as the magnocellular neuron directly
what are the circumventricular organs and what are their functions?
- organum vasculosum laminae terminalis (OVLT) and subfornical organ (SFO)
- these are a window through the BBB and test blood for various things. When high osmolarity is detected they stimulate the magnocellular neurons and cause release of AVP in a linear fashion.
What is the normal plasma osmolality, [AVP], and urine osmolality?
plasma: 287 mOsm/kg
[AVP]: 2.0 pg/ml
urine osmolality: 500 mOsm/kg
[AVP] changes linearly with _____ and exponentially with ______.
linear relationship with: blood osmolality
exponential relationship with: MAP; however, at any given bp the change in AVP remains linear
where are AVP receptors located in the kidney?
Cortical collecting duct and inner medullary collecting ducts.
What plays into the regulation of salt homeostasis, bp, and blood volume? (8)
- AVP
- ANP
- renin-angiotensin
- kinins
- NO system
- endothelins
- prostaglandins
- adrenergic NS
Central DI
Also referred to as neurogenic DI
- some complication with AVP production or secretion
- Usually its a genetic mutation but brain tumors are also common as well as autoimmune diseases
- If the stalk is severed then there can still be AVP release into blood since the H is synthesized in the hypothalamus
- often treated with AVP agonists
Nephrogenic DI
- Inability of the kidneys to use AVP whether its the inability of V2 receptors to bind AVP or a mutation in AQP2 synthesis
- Mutations are often associated with this and they are generally in the transmembrane areas of the receptors
How does oxytocin activate partuition?
- High progesterone throughout pregnancy decreases
- Causes both an increase in uterine oxytocin receptors and exocytosis of OT from magnocellular neurons
- upregulation of OT receptors in the uterus causes more OT that has now been secreted in the blood to bind and cause uterine contractions
