Anterior pituitary Flashcards
hypothalamic hormones
- small neurohormones (9aa):
-antidiuretic hormone (ADH or VP)
-oxytocin - releasing hormones + releasing-inhibiting hormones
A. stimulatory
-corticotrophin releasing hormone
-growth hormone releasing hormone
-gonadotrophin releasing hormone
-thyrotrophin releasing hormone
B. inhibitory
-dopamine
-somatotrophin
characteristics of releasing hormones
-secretion in pulses
-act on specific membrane receptors (G-protein coupled receptors)
-transduced signals via secondary messanger
-stimulates synthesis of pituitary hormones
-stimulates release of stored pituitary hormones
-stimulates hyperplasia & hypertophy of target cells in pit gland
hypophyseal portal system
-systems of blood vessels in the median eminence connecting the hypothalamus with the AP
-quickly transports hormones between the hypothalamic nuclei and AP
-communication between two tissue types
-uses parvocellular neurons
what are the specific cell populations of the AP
-gonadotrophs
-somatotrotrophs
-thyrotrophs
-corticotrophs
-lactotrophs
what is the most abundent cell type in the AP
somatotrophs
AP hormones journey
hormones produced by the AP (in response to releasing hormones) enter a secondary capillary system and from there drain into circulation
hormones hypothalamus releases and there corresponding anterior pituitary hormone
-GnRH->FSH + LH
-GHRH->growth hormone
-TRH->TSH
-CRH->ACTH
-SS->growth hormone
-DA->prolactin
target organs for AP hormones
-prolactin->mammary
-GH->muscles, bones
-TSH->thyroid
-ACTH->adrenal glands
-gonatotrophin (LH and FSH)->testis and ovaries
what cell in the AP makes which hormone
-gonadotrophs->LH+FSH
-somatotrophs->growth releasing hormone
-thyrotrophs->thyroid stimulating
-corticotrophs->ACTH
-lactotrophs->prolactins
growth hormone
-most abundant pit hormone (~40-50%)
-growth promoting actions on muscles and skeleton
1. direct effect are the result of GH binding tits receptor on target cells
2. indirect effects are mediated primarly by IGF-1
direct effects of growth hormone example
fat cells (adipocytes) have GH receptors and GH stimulates then to break down triglyceride and supress their ability to take up and accumulate circulating lipids
indirect effects of growth hormone example
IGF-1 secreted form the liver and other tissues in response to GH
AP hormones: prolactin
-breast development and production
-causes infertility excess amounts via inhabitation of GnRH
-dopamine inhibits secretion
-stress, exercise, suckling, pregnancy, inc estrogen = increased secretion
-basal level increases with sleep
-behavioural effects-maternal behaviour
-heavy lactation decreases GnRH which decreases FSH which decreases repro function
PT hormone: ACTH
-adrenocorticotropin hormone
-derived from proopiomelanocorin
-stimulates the adrenal cortex (or internal glands in non mammalian verts = corticosteroids
-responce to stress= fight or flight response; nutrient mobilization
-osmoregulation= sea water adaption in fish
-development= amphibian metamorphis
AP hormones: FSH
-folicle stimulating horm
-stimulates the proliferation of granulosa cells in the ovary
-binds to sertoli cells in the seminiferous tubules to induce spermatogenesis
-stimulates androgen binding protein
AP hormones: LH
stimulates cells of the theca cells, corpus luteum, and leydig cells to synthesize sex steroid hormones
AP hormones: TSH
stimulates thyroid cells to trap iodide and to synthesize and secrete thyroid hormones
