endocrine Flashcards
what are the properties of a hormone
cell to cell communication molecules
binding to target receptor initiate cellular response
communication eventually terminated
half life
what are the chemical classes of hormones
peptide/protein
steroid
amine
peptide/protein hormones
made in endocrine cells all over body
made in advance and stored in vesicles for release
preprohormone-prohormone-hormone
- initially made as a large, inactive preprohormone; includes one or more copies of the final hormone
- series of post-translational modification converts it
- online final hormone in vesicle is active
release into ECF via exocytosis, then diffuses from ECF to blood (carried away in solution)
short half life (sec-min)
lipophobic - binds membrane receptors (activates 2nd messenger systems)
response usually involves altered activity of target proteins
steroid hormones
made from cholesterol
only made in adrenal cortex, kidney, skin, gonads, placenta
final hormone is lipophilic so cannot be stored (will just diffuse out)
made on demand from lipophobic precursors that may be stored in intracellular compartments
released by simple diffusion into blood - transported bound to carrier proteins that bring them to target
longer half life (hours)
- intracellular response - slow genomic response = modulation/regulation of gene activity. change in gene expression
- membrane receptors - fast non-genomic response
Smooth endoplasmic reticulum
contain enzymes requires for steroid sythesis
lipid and lipid like storage
amine hormones
made in the pineal gland, adrenal medulla, thyroid
mostly derived from tyrosine
thyroid hormones, catecholamines
thyroid hormones
amine
characteristics similar to those of steroid hormones
lipophilic, made on demand from lipophobic precursors stored in thyroid, requires carrier proteins, long half life, genomic responses
catecholamine
amine
neurohormone
lipophobic, stored for release, short half life, change activity or target protein
gland
collection of secretory cells
exocrine
substance leaving the body
sweat
endocrine
going into the bloodstream - inside the body
alpha cell
secrete glucagon
beta cell
secretes insulin
what cellular processes could hormones regulate
rate of enzymatic rxns (speed/slow down)
transport of ions or molecules across cell membranes
gene expression and protein synthesis
posterior pituitary
neural tissue
secretes two neurohormones (vasopressin and oxytocin)
anterior pituitary
endocrine tissue secreting six true hormones synthesizes by endocrine tissue
what is release of hormones from anterior pituitary controlled by
neurohormones from the hypothalamus
how does the posterior pituitary glad secrete neurohormones
- neurohormone is made and packages in the cell body of the neuron
- vesicles are transported down the cell
- vesicles containing neurohormone are stored in posterior pituitary
- neurohormones are released into the blood
how does the anterior pituitary release hormones
- hypothalamic neurons synthesize neurohormones and release them into capillaries of the portal vein system
- portal veins carry the neurohormones directly to the anterior pituitary, where they act on the endocrine cells
- endocrine cells release their peptide hormones into the second set of capillaries for distribution to the rest of the body
portal circulatory system
specialized modification where two sets of capillaries are connected in series by a set of small veins
parathyroid hormone endocrine reflex loop
stimulus: low plasma [Ca2+]
integrating center: parathyroid cell (behind thyroid gland, moniters plasma calicum)
output signal: parathyroid hormone will be release to its targets
target: bone (has calcium) and kidney (filters calcium)
response: increase bone reabsorption, increase kidney reabsorption of calcium, production of calctriol leads to increased intestinal absorption of calcium
increased plasma calcium
insulin endocrine reflex loop for eating a meal
stimulus: stretch receptor in digestive tract
sensory neuron brings to integrating center CNS then the efferent neuron
integrating center: pancreas
beta cells release insulin (peptide hormone)
target cell: target tissues
tissue response: increase glucose uptake and utilization
systemic response: decrease blood glucose
insulin endocrine reflex loop for increase of blood glucose
integrating center: pancreas
beta cells release insulin (peptide hormone)
target cell: target tissues
tissue response: increase glucose uptake and utilization
systemic response: decrease blood glucose
insulin endocrine reflex loop for increase of glucose in lumen
glucose in lumen
endocrine cells i small intestine
GLP-1
integrating center: pancreas
beta cells release insulin (peptide hormone)
target cell: target tissues
tissue response: increase glucose uptake and utilization
systemic response: decrease blood glucose
modulations of cell responses
adjusting the number of receptors
cells can adjust their sensitivity to hormone in response to changes in hormone concentration
up regulation
increase receptor number in response to low hormone concentration
try to maintain response despite low hormone concentration
occurs when the body cannot synthesize enough of a hormone
down regulation
decrease receptor number in response to sustain increase in hormone
need to turn down the hormone since theres too much
usually involves endocytosis of membrane receptors
tropic hormone
control the secretion of another hormone
trophic hormone
hormone causing something else to grow
give an example of a tropic hormone
thyrotropin releasing hormone releases from the hypothalamus
causes release of thyrotropin (thyroid stimulating hormone; TSH) from anterior pituitary
causes release of thyroid hormones from thyroid
synergism
two hormones act together to have a greater effect
cells and tissues can be under the influence of multiple hormones at any given time, it is not always predictable
functional overlap of hormones
permissiveness
for a hormone to do their job they need the presence of another hormone
if hormone A can’t produce its full effect without the presence or hormone B, then B is permissive for A
functional antagonists
hormones with opposite actions
ligand
chemical molecule that binds to a receptor
agonist
a ligand that binds to a receptor and enhances its activity
may have the opposite effect in a different tissue
antagonist
a ligand that binds to a receptor and inhibits its activity
what is target cell response determined by
receptor and intracellular signalling pathways NOT on the ligand
specificity
receptors may show preference for a particular ligand or type of ligand
very specific - bind to few ligands
non-specific - able to bind to many different ligands (not at the same time)
competition
multiple ligands may compete for the same receptor active site
usually one ligand binds better than the other (higher affinity)
competitive antagonist
same binding site on receptor as agonist or primary ligand
can be overcome by an increase in agonist concentration
max response can still be achieved
non-competitive antagonist
different binding site on receptor (allosteric site) than agonist. changes the shape
or bind to the same active site but cannot unbind, permanently taking receptor out of the equation, irreversible antagonist)
cannot be overcome by increase in agonist concentration
when is the dose response curve maximal and saturated
if agonist concentration is high enough
