intro to endo 2 W6 Flashcards
endocrine reflex pathway stages?
stimulus
afferent signal
integration
efferent signal
physiological action
negative feedback
simple endocrine reflex pathway - parathyroid hormone?
low plasma calcium stimulates parathyroid cells to release parathyroid hormone which acts on bone and kidneys to increase reabsorption, and increases intestinal absorption. this leads to increased plasma calcium which feeds back negatively.
what are neurohormones
chemical signals released into the blood from a neuron
3 groups of neurohormones produced by the nervous system?
catecholamines (adrenal medulla)
hypothalamic neurohormones (posterior pituitary gland)
hypothalamic neurohormones (anterior pituitary gland)
endocrine structures incorporated into anatomy of the brain?
pineal and pituitary glands
pituitary gland anatomy?
infundibulum - stalk connecting pituitary to brain
posterior pituitary - extension of neural tissue
anterior pituitary - true endocrine gland of epithelial origin
other names for anterior/posterior pituitary?
anterior pituitary = adenohypophysis
posterior pituitary - neurohypophysis
posterior pituitary hormones released and their functions?
vasopressin (ADH) - regulation of water balance
oxytocin - ejection of breast milk, uterine contractions
how are posterior pituitary hormones released into circulation?
made and packaged in cell body of neuron in hypothalamus. vesicles transported down axon of cell into pituitary. vesicles stored in posterior pituitary and released into blood.
6 hormones released by anterior pituitary gland?
prolactin
thyrotropin (thyroid stimulating hormone)
adrenocorticotropin
growth hormone
follicle stimulating hormone (FSH)
luteinizing hormone (LH)
name for a hormone that controls the secretion of another hormone?
trophic hormone
what hormones control the release of anterior pituitary hormones?
hypothalamic neurohormones
these are trophic hormones but they are called releasing or inhibiting hormones
PRH causes what?
(PRH = prolactin-releasing hormone)
prolactin released from anterior pituitary targeting breast tissue (synthesise milk)
TRH causes what?
(TRH = thyrotropin-releasing hormone)
causes release of prolactin and TSH (thyroid stimulating hormone)
TSH acts on thyroid gland to release thyroid hormones acting on many tissues
CRH causes what?
(CRH = corticotropin-releasing hormone)
releases ACTH (adrenocorticotropic hormone)
ACTH acts on adrenal cortex to release cortisol which acts on many tissues
GHRH causes what?
(GHRH = growth hormone releasing hormone)
releases GH which acts on liver and many tissues
GnRH causes what?
(GnRH = gonadotropin-releasing hormone)
releases FSH and LH causing endocrine cells in gonads to release either androgens (males) or oestrogens and progesterone (females) which act on germ cells of gonads and many tissues
what does PIH stand for? what is this also known as?
prolactin-inhibiting hormone
also known as dopamine
GHIH stands for what?
growth hormone inhibiting hormone
HPT axis?
hypothalamic pituitary thyroid axis
HPA axis?
hypothalamic pituitary adrenal axis
HPG axis?
hypothalamic pituitary gonadal axis
3 levels of control - anterior pituitary?
hypothalamic stimulation (from CNS)
pituitary stimulation (from trophic hormones in hypothalamus)
endocrine gland stimulation (from trophic hormones in pituitary)
2 types of negative feedback control?
long-loop feedback - hormone released from final target cell feeds back to suppress anterior pituitary and hypothalamic hormones
short-loop feedback - pituitary hormones feed back to suppress hypothalamic hormone
negative control pathways for cortisol secretion?
short loop - ACTH inhibits hypothalamus
long loop - cortisol inhibits anterior pituitary and hypothalamus
set of blood vessels transporting hypothalamic trophic hormones to pituitary?
hypothalamic-hypophyseal portal system
what is a portal system?
specialized region of circulation consisting of two sets of capillaries directly connected by larger blood vessels
advantage of hypothalamic-hypophyseal portal system?
less dilution of hormone
smaller amount of hormone needed to elicit a certain level of response
delivered directly to target
only small number of neurosecretory hormones can effectively control activity of anterior pituitary
