Hypothalamus+Posterior Pituitary Flashcards
What are the products of the neurohypophysis?
Oxytocin and ADH (both 9 aa long)
Describe the embryology, structure, and movement of hormones in the hypothalamus/neurohypophysis.
- They are Neuroectodermal in origin
- 2 hormones made in hypothalamus, moved to neurohypophysis via Neurophysins
Explain the primary function of the hypothalamic hormones and their path to target Adenohypophyseal cells.
- mostly pumps out Releasing hormones (peptides, 1 catecholamine)
- short hypothalamic neurons secrete Releasing hormones into Pituitary portal system
- blood reaches Adenohypophysis, stimulates hormone release into circulation
What nuclei in the hypothalamus are intimately involved with the neurohypophysis?
- Paraventricular nucleus
- Supraoptic nucleus
Describe the creation/secretion of ADH and oxytocin.
- synthesized in the Nissl bodies of the neurons of the Paraventricular and Supraoptic nuclei
- travel down axon/infundibulum
- stored in granules (Herring bodies) in the axon terminal
- stimulation causes exocytosis into blood stream
What 2 stimuli cause release of Oxytocin?
- Uterus: distension of vagina+cervix
- Breast: suckling of infant
What are the target cells and function of Oxytocin?
- receptors on myoepithelial cells of breast (cause contraction of glands, milk ejection)
- receptors in the smooth muscles of uterus (causes parturition, menstruation, orgasm)
The oxytocin receptor is a ___________ which uses what second messenger system?
-Ga(q) - PLC - IP3, DAG - Ca - pkC
What stimuli cause release of ADH?
#1: plasma Osm (osmoreceptors in hypothalamus) #2: via drop in BP (heart and aortic R's)
What are the target cells, receptors, and function of ADH?
- V1R on vascular smooth muscle (vasoconstriction)
- V2R on principal cells of collecting duct (decrease urine volume by increasing water resorption in collection duct via AQP2 insertion on lumen side)
Describe the second messengers of the 2 Vasopressin receptors.
- V1R is a Ga(q) - PLC - IP3, DAG - Ca - pkC
- V2R is a Ga(s) - cAMP - pkA
What drugs are used to treat SIADH by blocking the V2R?
- drugs with -VAPTAN (conivaptan, tolvaptan)
- Demeclocycline, the antibacterial!
Peptide hormones are synthesized in a cell’s _____________, then cleaved by proteases and moved into the Golgi.
rER
After leaving the Golgi, what happens to peptide hormones?
they’re stored in vesicles awating release
Why can’t steroid hormones be stored in vesicles?
they are fat soluble, not water soluble (would degrade if stored at all)
