3 - Hypothalamo-neurohypophysial system Flashcards
Where do the nerve axons that come from the paraventricular nuclei terminate?
some terminate in the median eminence and some in the neurohypophysis
Where do magnocellular neurones originate from and terminate?
originate from cell bodies in the paraventricular and supraoptic nuclei
terminate in the neurohypophysis
Where do parvoocellular neurones originate from and terminate?
originate in the paraventricular nuclei and terminate in the median eminence and other parts of the brain
What is the name of the neurones that only terminate in the neurohypophysis?
magnocellular
What is the name of the neurones that terminate in the median eminence and other parts of the brain?
parvocellular
What type of neurones are supraoptic neurones?
magnocellular
What are paraventricular neurones?
have a magnocellular and a parvocellular component
- some of the neurones are parvocellular (pass to parts the brain or terminate in the median eminence)
- some are magnocellular (terminate in the neurohypophysis)
What kind of hormones are vasopressin and oxytocin?
peptide hormones
Where does the production of vasopressin from pre-porvasopressin occur?
in the nerve axons
How does the production of oxytocin differ from vasopressin?
it is broken down into 2 products
it has a slightly different neurophysin and does not have a glycopeptide
Where are the different types of vasopressin receptors found in the body?
V1a - found in vasculature and in the brain
V1b - found on adenohypophysial cells (cortiocotrophs)
V2 - kidney collecting ducts and are responsible for producing clotting factors
What is the mechanisms of action of a V1 vasopressin receptor?
- linked via G protein to phospholipase C (PLC)
- PLC coverts PIP3 to IP3 and DAG
- this increases the intracellular calcium conc and activates proteins kinase C (PKC)
What is the mechanism of action f V2 vasopressin receptor?
- linked via G protein to adenylate cyclase
- AC converts ATP to cAMP
- cAMP activates protein kinase A (PKA)
- PKA activates other intracellular mediators which produce cellular responses (recruitment of aquaporins)
There are 9 types of aquaporins. Which ones are impacted by vasopressin binding to V2 receptors?
AQ2 molecules - inserted into the apical membrane of the kidney collecting duct so water can move into the cells
AQ3 + AQ4 are the channels by which water moves out f the cells
(this necessitates the need for an osmotic gradient from the collecting duct, tough the principal cells and into the blood)
What are the 2 major stimuli of vasopressin?
increased plasma osmolality
low blood pressure
