Pituitary Gland Flashcards
Peptide hormones?
synthesised as PROHORMONES requiring further processing; Regulatory secretion (stored in vesicles); bind to cell membrane receptors (2nd messenger system)
Steroid hormones?
synthesised from cholesterol; Constitutive secretion (released immediately); act on intracellular receptors
What is the Anterior Pituitary?
Adenohypophysis, endocrine cells that produce various hormones
How are AP hormones produced?
short parvocellular neurons in hypothalamus secrete Releasing/Inhibiting hormones in median eminence. Regulatory factors carried to AP via hypothalamo-pituitary portal circulation.
AP cell types and hormones?
Somatotrophs -> Growth Hormone Lactotrophs -> Prolactin Thyrotrophs -> TSH Gonadotrophs -> LH/FSH Corticotrophs -> Adrenocorticotrophic hormone ACTH
GH regulatory factors?
+ GHReleasing Hormone, - Somatostatin
Prolactin regulatory factors?
- Dopamine
TSH regulatory factors?
+ TRH, - T4, - T3, - SS
LH/FSH regulatory factors?
GnRH
ACTH regulatory factors?
Corticotrophin RH, AVP
Possible effect of pituitary tumour?
Bitemporal Hemianopia: reduced lateral field vision due to compression of optic chasm (where nasal retinae fibres cross)
Excess GH in childhood?
Gigantism: excess production of GH results in abnormal growth (potentially caused by GH secreting AP tumour)
Excess GH in adulthood?
Acromegaly: macroglossia (tongue biting, altered speech, dysphagia), increase in hand/foot size, sweatiness, headache, larger facial features
What is Posterior Pituitary?
Neurohypophysis, nervous tissue continuous with hypothalamus, Oxytocin + AVP produced
How are Oxytocin + AVP produced?
long magnocellular neuron fibres originate in hypothalamus and end in PP, neurosecretory cells secrete hormones when stimulated by excitation
Where are magnocellular neurons?
Supraoptic nucleus (AVP), Paraventricular (oxytocin)
AVP mechanism of action?
AVP stimulates reabsorption of water in collecting duct by binding to V2 receptors -> G protein coupled receptor transducer signal to move more aquaporin-2 into apical membrane
oxytocin mechanism of action in breasts?
contractor hormone, stimulates breast myoepithelial cells to contract, ejecting milk
oxytocin mechanism of action in uterus?
contractor hormone, stimulates myometrial cells to contract to push baby out of womb
