The anterior pituitary system Flashcards
what is the appearance of the pituitary gland
hypophysis
sella turcica - Turkish saddle
very close to hypothalamus
what is the difference between the posterior and anterior hypothalamus
A - need blood supply, adenohypophysis, grows up from mouth
P - developed from neural tissue, down grow from neurons of hypothalamus, doesn’t require circulation
what is a hypothalamic nuclei
collection of neuronal cell bodies
describe the region of median eminence
devoid of the blood brain barrier - communicate with systemic circulation
what is the Pars tuberalis
it is wrapped around the pituitary stalk
what is the Pars distalis
body of the pituitary gland
what is the adenohypophysis made of
secretory cells
what is the neurohypophysis made of
extensions of hypothalamic nuclei - mainly nerve axons and nerve terminals
what important functions does the hypothalamus do
temp regulation
control appetite
describe the hypothalamic - hypophysial portal circulation
hypothalamus tell ant pit what to do - neurons release hormones
blood enters superior hypophysial artery into primary capillary plexus (fenestrated) in median eminence
down long portal veins
into secondary capillary plexus (fenestrated) in At. Pit
fenestrations - leaky - allows secretions
circulation hormone out of a pit into circulation
summarise the 3 stages of hypothalamic - hypophysial portal circulation
- hypothalamic neurosecretion into hypothalamo-hypophysial portal system
- hypothalamic neurosecretion acts on anterior pituitary target cells
- release of adenohypophysial hormone into general circulation by exocytosis
how many adenohypophysial cells are there
5
what are the adenohypophysial cells and what hormones do they produce
somatotrophs - growth hormone (somatotrophin)
lactotrophs - prolactin
thyrotrophs - throid stimulating hormone (TSH)
gonadotrophins - LSH, FSH
corticotrophs - adrenocorticotrophic hormone (corticotrophin/ACTH)
which adenohypophysial hormones are proteins
GH
prolactin
which adenohypophysial hormones are glycoproteins
TSH
LH
FSH
(B same in all, a chain differs in TSH compared to LH and FSH)
which adenohypophysial hormone is a polypeptide
ACTH
which hypothalamic hormones affect GH
growth hormone releasing hormone (GHRH) - stim
somatostatin (SS) - inhib
on and off
which hypothalamic hormones affect prolactin
-ve control
dopamine - inhib
thyrotropin releasing hormone (TRH) - stim
which hypothalamic hormones affect TSH
TRH - stim
which hypothalamic hormones affect LH and FSH
gonadotrophin releasing hormone (GnRH)
which hypothalamic hormones affect ACTH
corticotrophin releasing hormone (CRH)
vasopressin to some extent
target cells of adenohypophysial hormones
GH - general and liver prolactin - breasts thyrotropin - thyroid LH and FSH - testes, ovaries ACTH - adrenal cortex
describe the actions of GH
bind directly to bone and muscle receptors - anabolic effects
bind to liver - somatomedins IGF1 - mediate - bind to IGF1 receptors - indirectly affect growth
stim AA into cell, protein synth
increased gluconeogenesis - diabetes stimulate lipolysis - increased fatty acid production
increased cartilaginous growth and somatic cell growth - cancer
what affects GH
sleep stress oestrogen exercise fasting AA (arginine) Ghrelin -ve feedback from output to hypothalamus and ant pit and from ant pit to hyp
describe the neuroendocrine reflex arc - prolactin
neural stimulation of tactile receptors
feedback to hypothalamic dopaminergic neurons by suckling - suppresses them and so dopamine meaning prolactin is released
what mediates the action of peptide hormones
intracellular protein kinases
