pack Flashcards
What are the two hormones that are synthesized in the posterior pituitary?
ADH
Oxytocin
What are the neurosecretory cells that project from the paraventricular nucleus and the Supraoptic nucleus down the infundibulum?
The Hypothalamo hypophyseal tracts
What are the cell bodies of the paraventricular and supraoptic nuclei called?
magnocellular
Where do the axons of the SON and PVN terminate in the neurohypophysis and what other cell type is present?
They terminate in the pars nervosa
Other cell type: Pituicytes are present (glial-like cells)
What is the function of pituicytes?
They are support cells that aid in the storage and secretion of ADH and oxytocin
How does the synthesis of ADH and oxytocin take place?
ADH and oxytocin are synthesized as preprohormones (Hormone-neurophysin-glycopeptide-Signal)
As soon as the mRNA for the preprohormones is translated, the signal gets cleaved in the ER, leaving us with a prohormone (Hormone-neurophysin-glycopeptide)
The prohormone travels to the golgi where it is seperated further into its 3 different parts
What are the preprohormones for oxytocin and ADH called accordingly?
oxytocin: Preprooxyphysin
ADH: Preprovasophysin
What is the type of neurophysin that is bound to ADH and oxytocin accordingly?
ADH: Neurophysin II
Oxytocin: Neurophysin I
Where are Secretory granules containing fully processed
peptides located?
In the axonal termini
What are herring bodies?
Are the expansions in the axonal termini due to the secretory granules filling up
Does oxytocin intiate parturtion?
No its does not (Remember Dr.Simons lecture)
What do progestrone and estrogen do in relation with oxytocin receptors?
Progestrone: Inhibts receptor production
Estrogen: Stimulates receptor production
How does the suckling reflex aid in oxytocin release and what does oxytocin do in breastfeeding?
The suckling reflex stimulates sensory neurons in the breast which sitmulates the secretion of oxytocin.
Oxytocin stimulate myoepithelial contraction which aids in milk ejection
What is the reflex of oxytocin aiding milk ejection called?
Milk let down reflex
or
Milk ejection reflex
What does prolactin do in relation to LH and FSH?
Inhibits LH and FSH production leading to lactational amenorrhea
Where are osmoreceptors located?
In the SON and PVN in the anterior hypothalamus
What happens to ADH secretion when the ECF becomes hypertonic?
Cells shrink and ADH secretion increases
You can remember cell shrinking bc they empty ADH (secreting it)
What happens to ADH secretion when the ECF becomes hypotonic?
Cells swell and ADH secretion decreases
You can remember cell swelling bc they fill up with ADH Not secreting it
State the effect on ADH
What is the defintion of the set point regarding ADH release?
Below the osmolality set point virtually no ADH is released
What is the average set point in healthy adults?
it varies from 275 to 290 mOsm/kg H 2 O (average, ≈280 to 285 mOsm/kg H 2 O)
What does pregnancy do to the set point?
Decreases it
How do V2 receptors play a role in regulation of water reabsorption?
When ADH binds to V2 receptors intracellular levels of cAMP increases
This increase results in the activation of Protein Kinase A
The activation of PKA causes AQP2 channels to be inserted into the external membrane of the cell and it also increases the production of AQP2
This in turn causes increased reaborption of water
