intro to endocrine hormones Flashcards
definition of endocrine system
system that integrates + controls organ function via secretion of hormones from cells, tissues/glands, which are then carried in blood to target organs, distal to site of synthesis, where they influence the activity of target organs
what are bodily functions controlled by?
endocrine and nervous system
describe nervous mode of communication?
neurotransmitters (chemicals) released by neutron, act locally in synaptic cleft, not released into blood
describe endocrine mode of communication?
travel via blood, hormones detected by specific receptors on target tissues - no receptor, no response
describe neuroendocrine mode of communication?
nerves release hormones into blood
example of neuroendocrine mode of communication?
hypothalamic-posterior pituitary axis
can hormones have more than 1 target cell?
yes - can have multiple target cells, different target cells have different responses to the same hormone
describe effect of insulin in skeletal muscle and adipose tissues
increases the uptake go GLC
describe effect of insulin in the liver
when increased levels of GLC, there is an increase in glycogenesis - i.e.turning GLC to glycogen as storage - and a decrease in glucogenesis
describe autocrine signals
cells secrete chemicals that blind to receptors on the SAME cell - not in blood and have a localised response
describe paracrine signals
chemicals diffuse in ExtraCellularFluid to affect other cells - not in blood and have a localised response
function of hormones and neurotransmitters
to bring about changes in activity of target cells and tissues - i.e. to increase/decrease an activity
6 features of endocrine hormone?
1 - produced by cells
2 - secreted into blood
3 - transport to distal sites via blood
4 - exert effects at low conc. : x10-9 - x10-12
5 - act by binding to receptors on target tissues
6 - action is determined (-ve feedback loops)
classes of endocrine hormone
peptide
amine
steroid
describe peptide hormones
most common
made of amino acids
describe amine hormones
derived from either tryptophan OR tyrosine
describe steroid hormones
derived from cholesterol
example of paracrine signal?
histamine - local site of action
where are neurohormones released?
hypothalamus - a neuroendocrine tissue
where are preprohormones (peptide) synthesised and then cleaved?
synthesis - ribosomes
cleaved into pro hormone - endoplasmic reticulum
cleaved by enzymes into active hormones - Golgi apparatus
why is it useful to measure C-peptide and not insulin?
C-peptide shows insulin naturally produced by pancreas at that time, regardless of insulin administered
solubility of peptide hormone?
H2O soluble - therefore need to bind to receptors on cell surface in order to cross membrane,
also has v fast response and dissolves easily in plasma
what pathways do peptide hormones modulate?
GPCR or tyrosine kinase linked receptor pathway
what are the 3 catecholamines and what type of molecule is each? (AMINES)
dopamine - hormone & neurotransmitter
norepinephrine - hormone & neurotransmitter
epinephrine - hormone
where is epinephrine released?
adrenal medulla
amines - thyroid hormones - name these 2 hormones
thyroxine
triiodothyronine
how to thyroid hormones act?
like steroids
function of melatonin? (AMINE)
regulates circadian rhythm
where is melatonin released?
pineal gland
what is the only amine hormone derived from tyrosine?
melatonin
how do steroids move to target sites?
bind to carrier proteins e.g. albumin
how do steroids differ to peptide/amine hormones?
they are made as needed - not stored
how do steroids bind and what is the consequence of this?
bind to intracellular receptors -
slower onset of action and remain for a longer period
what are the 4 tissues steroids are produced by?
Gonads
Placenta
Adrenal cortex
Kidney
why is there a cross effect of steroids at high doses?
all have common ancestry of cholesterol
solubility of steroids?
lipophyllic - therefore cross cell membrane easily
which hormone is the active form?
the free hormone - only these can diffuse to target cells
example of -ve feedback loop?
parathyroid hormones - Ca2+
best way to monitor hormones in body?
24hr monitoring
example of neural feedback loops?
adrenaline
