Hypothalamus-Pituitary Interactions Flashcards
What are the two parts to the pituitary gland?
Adenohypophysis (anterior) - epithelial tissue, formed from embryonic pharynx
Neurohypophysis (posterior) - neural tissue, formed from embryonic brain
What type of neurons are located in the supraoptic and paraventricular and what do they release?
Magnocellular neurons - pass through the infundibulum and terminate in close proximity to the capillaries
Release ADH and Oxytocin
*Posterior Pituitary
How are vasopressin and oxytocin synthesized?
Preprohormones
Contain: a signal peptide, hormone sequence, neurophysin domain, and glycopeptide domain (ADH only)
What are neurophysin domains?
Domains that are cleaved from the prohormone that bind the hormone and function as intraneuronal carriers
No know physiological function outside of ADH- and Oxytocin-secreting neurons
Describe stimulation-secretion coupling
Depolarization of the neurosecretory cell triggers the opening of voltage-gated Ca channels
Leads to exocytosis of secretory product
What regulates oxytocin and vasopressin secretion?
Regulation of secretion is under direct neural control
Neurons releasing vasopressin and oxytocin represent the efferent limbs of neuroendocrine reflex arcs
How is anterior pituitary secretory function regulated?
Hypothalamic control mediated by hypophysiotropic hormones
Also called releasing hormones or release-inhibiting hormones
Released into the primary capillary plexus of the median eminence, and travel to specific cells in the anterior pituitary
CNS exerts strong regulatory influences of anterior pituitary function
Describe the hypothalamic control of prolactin release
Prolactin is unique in that it is under tonic inhibition by dopamine
Definitive prolactin-releasing hormone has yet to be identified
Clinically, TRH administration may be used as a stimulation test for PRL release
What is the mechanism of hypophysiotropic hormones action on anterior pituitary cells?
Work through G-protein coupled receptors
What are tropic hormones?
Hormones that regulate the activity of other endocrine glands
Many anterior pituitary hormones are tropic hormones
What are axis-driven feedback loops?
Hormones released in response to stimulation of a target gland by a tropic hormone regulate the release of these tropic hormones by exerting negative feedback effects on the anterior pituitary and/or hypothalamus
Tropic hormones can also inhibit their own release
