lecture 20-endocrine principals Flashcards
what do negative feedback loops do
prevent over-activity of hormone systems
what is the controlled variable in feedback loops
the degree of activity of the target tissue
what periodic variations in hormone release are superimposed on the negative and positive feedback mechanisms
seasonal changes and various stages in development and aging
what does down regulation do
decreases the target tissue’s responsiveness to the hormones
what does up regulation of receptors do
increases the target tissue’s responsiveness to the hormones
what are ion-channel-linked receptors used primarily by
neurotransmitters
describe the receptor part of the enzyme-linked hormone receptor
it is extracellular
where are polypeptide and protein hormones stored until needed
secretory vesicles
what are polypeptides and protein hormones usually synthesized as
preprohormones
how are polypeptide and protein hormones released
via exocytosis
what are amine hormones derived from
tyrosine
what occurs when calcium ions bind with calmodulin
activation of protein kinases; inhibition of protein kinases
calcium entry may be initiated by (for calcium-calmodulin phospholipid second messenger system)
changes in membrane potential that open calcium channels and a hormone interaction with membrane receptors that open calcium channels
what hormones act directly on DNA
steroid and thyroid hormones
what is an example of a somatotropes
HGF
what is an example of a corticotropes
ACTH
what is an example of a thyrotropes
TSH
what is an example of a gonadotropes
LH and FSH
what is an example of a lactotropes
Prolactin
where are magnocellular neurons located
in the supraoptic and paraventricular nuclei
where is ADH primarily formed
supraoptic nuclei
where is oxytocin primarily formed
in paraventricular nuclei
when is the increased secretion of GH important under chronic conditions
during starvation
what type of conditions of hypoglycemia is GH most important to be released
acute conditions
