OC1 - endocrine system Flashcards
what is homeostasis?
the maintenance of the body’s internal environment within narrow physiological limits.
what is negative feedback?
corrects any deviations of the internal environment from physiological set points
the response diminishes the original stimulus
what is positive feedback?
the response enhances the original stimulus.
what are the feedback mechanisms?
thermoregulation
control of blood glucose levels
osmoregulation
growth hormone and blood glucose
thyroid regulation
what happens during thermoregulation when there is an increase in body temperature?
detected by thermoreceptors in the hypothalamus
the autonomic nervous system relays information to effectors
blood vessels dilate, sweat glands secrete fluid
heat is lost to the environment
decrease in body temperature
what happens during thermoregulation when there is a decrease in body temperature?
detected by thermoreceptors in the hypothalamus
the autonomic nervous system relays information to effectors
blood vessels constrict, muscle contractions (shivering), release of adrenaline and thyroxine
increase in metabolic rate, generating heat
increase in body temperature
thermoregulation feedback mechanism
pathway…
what happens in the control of blood glucose when there is an increase in blood glucose?
cells in the pancreas detect change
insulin is released by beta cells
effectors in the liver respond
glucose is converted to glycogen
glycogenolysis is inhibited
normal blood glucose concentration
what happens in the control of blood glucose when there is a decrease in blood glucose?
cells in the pancreas detect change
glucagon is released by alpha cells
effectors in the liver respond
glycogen is converted to glucose
glycogenolysis
normal blood glucose concentration
control of blood glucose feedback mechanism
pathway…
what happens during osmoregulation when there is an increase in water content?
osmoreceptors in the hypothalamus detect change
pituitary gland produces less ADH
kidneys decrease permeability of tubules to water
less water is reabosrbed
large volume of dilute urine
what happens during osmoregulation when there is a decrease in water content?
osmoreceptors in the hypothalamus detect change
pituitary gland produces more ADH
kidneys increase permeability of tubules to water
more water is reabosrbed
small volume of concentrated urine
osmoregulation feedback mechanism
pathway…
what happens during growth hormone and blood glucose when there is low blood glucose?
hypothalamus stimulates GHRH
GHRH stimulates GH from anterior pituitary
GH speeds up liver glycogen to glucose (glycogenolysis)
raises blood glucose
if blood glucose gets too high release of GHRH is inhibited
what happens during growth hormone and blood glucose when there is high blood glucose?
hypothalamus stimulates GHIH
GHIH inhibits secretion of GH from anterior pituitary
low levels of GH lowers rate of glycogen breakdown
lowers blood glucose
if blood glucose gets too low release of GHIH is inhibited
