intro to endocrine Flashcards
what does endocrine system do?
regulate multiple organs to meet growth and reproduction demands
what are the classic endocrine organs?
hypothalamus
pituitary
thyroid
parathyroid
adrenal
gonads
endocrine pancreas
placenta
which orgnas make hormones but thats not their main function?
adipose
heart
liver
kidney
GI Tract
which hormones are modified peripherally
angiotensin II, vitamin D
what are the three categories of hormones?
protein
steroid
amines
whats special about peptide hormones?
stored in secretory vesicles
water soluble
more than 100 aa, proteins
less than 100aa, peptides
whats special about steroid hormones
made from cholesterol
lipid soluble
not stored
where do amine hormones come from?
tyrosine
how are peptide hormones made?
made from preprohormone
in ER this becomes prohormone
this is packed into vesicles
enzymes cleave this to form functional hormone
what causes release of peptide hormone from secretory vesicles?
endocrine cell stimulus causes release of hormone
more intracellular Ca
increased cAMP and PkA
where are steroid hormones made?
adrenal cortex
gonads
corpus luteum
placenta
how are steroid hormones made?
from cholesterol
add or remove side chaines
hyroxylate or aromatize steroid nucleus
what are the two groups of amine hormones?
catecholamines
and
thyroid hormones
how are catecholamines made? how do they act
made in cytosol and secretory granules
act through cell membrane receptors
how are thyroid hormones made? how do they act
made in thyroid , stored as thyroglobulin in follicles
act as nuclear receptors
explain the neural mechanism of secretion
give an example
neural input to endocrine cell increases or decreases secretion
example: sympathetic preganglionic innervation of adrenal medulla: causes catecholamines to be released
explain the feedback mechanism of secretion
most common
element of pathway feeds back on endocrine to change secretion rate
explain positive feedback
hormonal action causes more hormone to be made
leads to explosive event, such as ovulation
explain negative feedback
most common
hormone inhibits further secretion of hormone
gives stability by keeping a barrier to physiology
what is long loop feedback
3rd tier feeds back to 1st and 2nd tier
what is short loop feedback
2nd tier hormone feeds back to 1st tier
what is ultra short loop feedback
gland inhibits its own secretion
how is hypothalamus regulated?
by descending and ascending neuronal inputs
what are the major inputs to regulate the hypothalamus, what do they do?
SCN: circadian rhythm on secretion of hypothalamic hormone release
Pineal: releases melatonin, which feedbacks to SCN regarding day and night
physiological stress influences hypothalamus
what confers specificity to hormone actions?
hormone receptor complex
responsiveness to target tissue is expressed as what?
dose response relationship
concentration that produces 50% of maximal response is senitivity
how can hormone responsiveness be changed?
change the # of receptors
change the affiniy of receptors for the hormone
when does upregulation happen and how?
when hormone levels are low
increase the number of receptors
decrease degradation of existing receptors
activate receptors
when doe downregulation happen and how?
too much hormone
decrease receptor synthesis
increase degradation of receptors
inactivate receptors
what hormones use AC as their effector? whats he secon messenger? second effector?
ACTH, LH, FSH, TSH, Glucagon
2nd mess: cAMP
Secon effector: PKA
what hormones use phospholipase C as their effector? whats he secon messenger? second effector?
GnRH, TRH, oxytocin
2nd messenger: IP3/DAG/Ca
2nd effector: PKC or calmodulin
what are the 6 steps of steroid hormone action?
- unbound hormons fuse into target cell only
- receptors are in cytoplasm or nucleus
- binds to DNA, repress or activate genes
- activated genes make mRNA, goes to cytoplasm
- translation produced new protein
6steroid hormones bind to receptors that use second messenger systems to create rapid cell responses
what does guanalyl cyclase do
converts GTP to cGMP
results in relaxation of vascular smooth muscle (NO)
what do receptor tyrosine kinases do?
have tyrosine kinase activity
phosphorylates downstream proteins
what do tyrosine kinase associated receptors do?
associate non covalently to proteins that have kinase activity
phosphorylates downstream proteins
what is autocrine?
acts on itself
what is paracrine
acts on cells near it
what is endocrine
acts on cells through blood stream
what is neuroendocrine
nerve acts on cells through blood stream
