module 7 hormones Flashcards
pituitary
also called hypophysis
anterior and posterior lobes
anterior pituitary hormones ( adenohypophysis)
FLATPiG FH (follicle stimulating) LH (leutenizing hormone) ACTH (adrenocorticotropic hormone) TSH (thyroid stimulating hormone) Prolactin GH (Growth hormone)
FH and LH
responds to GnRH (gonadotropin-releasing hormone)
target ovary and testis
negative feedback: estrogen, progesterone, testosterone, inhibin
ACTH
adrenocorticotropic hormone
respondes to CRH ( corticotropin-releasing hormone)
target: adrenal cortex
negative feedback: cortisol
TSH
thyroid stimulating hormone
responses to TRH (thyroid releasing hormone)
target: thyroid
negative feedback: triodothyronine: T3
Prolactin
responds to -prolactin-releasing factor (stimulatory) -dopamine (inhibitory) no target organ no negative feedback
GH
growth hormone responds to - GHRH: growth hormone releasing hormone (stimulatory) - somatostatin (inhibitory) target: liver, but also direct actions negative feedback: IGF-1
posterior pituitary hormones (neurohypophysis)
ADH
oxytocin
hormones are released
in response to an alteration
to maintain regulated level
feedback systems
positive: self-amplifying
negative: inhibitory
neurocrine
neuronal travel to target cell
endocrine
through blood to target cell
paracrine
through interstitial fluid to work on cells in local area
autocrine
works on self
steroid hormone derived from
cholesterol
lipid soluble hormones
Steroid hormones
- androgens, estrogens, glucocorticoids, mineralcorticoids, thyroid hormones
- diffuse across plasma membrane
- activate: RNA polymerase, DNA trascription and translation
- require transport proteins
water soluble hormones
first messenger signal transduction second messenger - G-Protein-coupled receptors --Ca -- cAMP -- cGMP
protein kinase receptors
either become activated kinases themselves or are associated with cytoplasmic kinases
amplification
process of intracelluar activation by secondary messenger occurs via cascade effect
- progressively larger number of chemical reactions at each step
Thyroid hormone: T3, T4
cross membrane with protein carrier
steroid hormones
diffuse across membrane
Most endocrine hormones are
polypeptides manufactured on rough ER and stored in vesicles
thryoid and steroid:
- production closely precedes hormone release
-TH trapped in thyroid, bound to thryoglobulin: water soluble protein, must be cleaved for secretion to occure
feedback control
most common: negative feedback
- some aspect of secreted hormone is sensed and regulated further secretion
- maintains hormone within normal range or set point
negative feedback regulation
possible at 3 levels
- target organ (ultrashort feedback)
- anterior pituitary (short feedback)
- hypothalamus ( long feedback)
positive feedback
self-amplifying
labor
baby pushed on cervix -> stretching of cervix -> release of oxytocin -> uterine contractions -> baby pushing on cervix
metabolism and secretion of hormones
degraded and excreted by liver and kidneys
- water-soluble in urine
- lipid-soluble bound to plasma proteins and stored in adipose tissue, less readily metabolized
some hormones degraded by target cell after binding
regulation of receptor responses
specificity
affinity
specificity
molecular “fit” of a hormone within receptor binding pocket
affinity
degree of “tightness” of hormone receptor bond, or inclination of hormone to remain bound.
- receptors attraction to hormone
- increased affinity = decreased amount of hormone needed to produce effect
up-regulation
increased number of receptors on target cell
permissive effects of hormones
one hormone needed for another to have effect
- cortisol enhances action of glucagon
down-regulation
decreased number on receptors on target cell
hormone antagonist
binds to receptor without causing effect, blocking agent
hormone agonist
binds to hormone receptor and causes same intracelluar response
