Review of Endocrine Flashcards
(28 cards)
what Is insulin released from?
pancreatic B cells
what stimulates the release of insulin?
- Raised blood glucose (direct effect on β cells)
- Raised blood amino acids (arginine)
- Parasympathetic (vagal) nerve activity
- Raised blood CCK, gastrin, incretins (feedforward)
what inhibits the release of insulin?
- Low blood glucose
- Sympathetic nerve activity (e.g. exercise)
- Raised blood cortisol (to maintain blood glucose)
what are the actions of insulin?
- Stimulates glucose uptake into muscle & fat (GLUT4)
- Promotes glycogen synthesis in liver
- Stimulates amino acid incorporation into protein (muscle)
- Promotes lipogenesis, inhibits lipolysis
- Hormone of the fed state - anabolic
what is glucagon released from?
pancreatic Alpha cells
what stimulates the release of glucagon?
- Decreased blood glucose (direct effect on α cells)
- Amino acids (raises blood glucose after protein meal)
- Decreased blood fatty acids
- Sympathetic nerve activity (e.g.exercise)
- Cortisol (to aid raising blood glucose)
what inhibits the release of glucagon?
- Raised blood glucose
- Raised blood fatty acids
- Insulin
what are the actions of glucagon?
- Increases liver glycogenolysis (blood glucose rises)
- Inhibits liver glycogen synthesis
- Promotes lipolysis in liver & adipose tissue
- Promotes liver gluconeogenesis
- Hormone of the unfed state - catabolic
what are glucocorticoids released from?
Adrenal cortex (zona fasciculata)
what stimulates the release of glucocorticoids?
- Circadian (ACTH bursts, most frequent in morning)
- Stress (via hypothalamic CRH and ant.pit. ACTH)
- Low plasma cortisol - long & short loop feedback
what inhibits the release of glucocorticoids?
- Depression of ACTH in evening
- High plasma cortisol - long & short loop feedback
- Low stress
what are the actions of glucocorticoids?
- Raises blood glucose
- Promotes liver glycogenolysis and gluconeogenesis
- Promotes protein breakdown
- Promotes lipolysis
- Permissive action on vascular adrenoceptors
- Essential for resisting stress
what releases adrenaline (epinephrine)?
Chromaffin cells of adrenal medulla
what stimulates the release of adrenaline?
Sympathetic nerve stimulation (“fight or flight”)
what inhibits the release of adrenaline?
Inhibition of sympathetic nerve stimulation
what are the actions of adrenaline?
- Promotes liver and muscle glycogenolysis
- Promotes lipolysis (raises blood FFAs)
- Raises metabolic rate
- Chronotropic & inotropic effects on heart (β1)
- Dilates coronary & skeletal muscle arterioles (β2)
what releases the growth hormone?
anterior pituitary gland
what stimulates the release of the growth hormone?
- Deep sleep – release greatest at night (GRH surges)
- Deficiency in energy substrates (exercise, fasting)
- Increased AAs in blood (e.g. arginine, leucine)
what inhibits the release of the growth hormone?
- Plentiful metabolic substrates (glucose, FFAs)
- Cortisol (to offset GH effect on protein anabolism?)
- Hypothyroidism (permissive action of T3)
- REM sleep
what are the actions of the growth hormone?
- Promotes growth via IGFs (bone & lean body mass)
- Promotes AA uptake & net protein synthesis
- Increases blood glucose (raises output from liver & has “anti-insulin” effect on muscle)
- Promotes lipolysis (raises blood FFAs)
what releases thyroid hormones?
thyroid glands
what stimulates the release of thyroid hormones?
- Plasma levels usually steady – negative feedback control of TSH
- Prolonged exposure to cold in infants – TRH release
what inhibits the release from thyroid hormones?
- Plasma levels usually steady – negative feedback control of TSH
- Prolonged exposure to heat
what are the actions of thyroid hormones?
- Set Basal Metabolic Rate
- Increased levels raise metabolic rate
- Promote protein & fat catabolism
- Raise body temperature – “ calorigenic action”
- Essential for normal development of CNS in foetus
- Permissive effect on growth hormone
- Permissive effect on β adrenoceptors – increase number & affinity to catecholamines
