endocrine control 1 Flashcards
humoral activation of hormone release
endocrine organ respons to changing levels of ions or nutrients in the blood
neural activation of hormone release
stimulation by nerve eg. fight or flight secreted noradrenaline and adrenaline
hormonal activation of hormone release
stimulation received from other hormones
3 types of hormones
hydrophilic - protein/peptide hormone
really small variable -tyrosine-derived hormone
hydrophobic - steroid hormone
steroid hormones
testosterone estradiol progesterone cortisol aldosterone vitamin D
protein/peptide hormones stored in
secretory granules or vesicles
exocytosis release
protein/peptide hormones
hydrophilic - bind cell surface receptors and activate intracellular signalling paths
rapid acting, short lived
inactivation of protein/peptide hormones
internalised by receptor mediated endocytosis
sequestered by kidney - excreted
steroid hormones
lipids - derived from cholesterol
lipophilic - required transport proteins, bind intracellular receptors
types of steroid hormones
cortisol, aldosterone, testosterone and progesterone
inactivation of steroid hormones
inactivated in the liver
- cytochrome P450 oxidase
- conjugated
- excretion in bile
steroid secreting cells
have abundant smooth ER - as opposed to rough endoplasmic reticulum in protein secreting cells
steroid directly diffused across plasma membrane - not exocytosis
abundant lipid droplets - raw material from which steroids are made
steroid can directly diffuse across
plasma membranes
steroid hormones bind
intracellular receptors
tyrosine derived hormones
thyroid hormone, adrenaline, noradrenaline, dopamine
lili soluble
inactivated by enzymatic degradation
need carrier proteins, bind intracellular receptors (behaves like a steroid)
inactivation of tyrosine derived hormones
enzymatic degradation by COMT and MAO
thyroid hormones bind
nucelar receptors
dopamine, adrenaline, noradrenaline bind
extracellular receptors
sensitivity is determined by
- number of receptors
- affinity of the receptor
- down stream signalling molecules
the capacity to response (maximal response) is determined by
the number of functional cells
overload desensitisation
prolonged exposure to stimulate decrease cells response to the level of exposure
allows receptors to response to changes in concentration of a signal rather than absolute concentration
HPX axis
hypothalamus, pituitary, end organ
neural part of the pituitary
posterior pituitary
anedohypothesis
anterior pituitary - glandular
produces hormones and secretes them
hypothalamic hypophyseal tract
tract of neurons
reach down to the posterior pituitary
hypothalamic hypophyseal portal
hypothalamus controls anterior pituitary by releasing tropic hormones into the blood stream into the portal vessel
high local concentration of local trophic hormones delivered quickly
posterior pituitary controlled by
hypothalamus hypophyseal tract
anterior pituitary controlled by
hypothalamic hypophyseal portal
posterior pituitary main hormones
hormone synthesis in hypothalamus, travel down the axon to PP
released into capillaries when stimulated
oxytocin - acts of the breasts and uterus, involved in control of lactation and uterine contraction
ADH - antidiuretic hormone, vasopressin, involved in H2O re-absorption in kidney
hypothalamus controls anterior pituitary by
releasing hormones
- travel to adenohypophysis via hypothalamic hypophyseal portal circulation
travel to specific cells in anterior pituitary to stimulate synthesis and secretion of trophic hormones
corticotropin releasing hormones CRH
stimulates ACTH secretion
thyrotropin releasing hormone TRH
stimulates TSH and prolactin secretion
growth hormone releasing hormone GHRH
stimulates GH secretion
somatostatin
inhibits GH and other hormone secretion
gonadotropin releasing hormone GnRH
stimulates LH and FSH secretion
prolactin releasing hormone PRH
stimulates PRL secretion
dopamine
inhibits PRL secretion
