Endocrine Flashcards
what is an endocrine secretion
secretion from groups of cells organised into endocrine glands
where do endocrine glands release secretions
into extracellular fluid which then moves into the blood stream
ductless
where do exocrine glands release secretions
into ducts
how are hormones transported around the body
dissolved in blood
attached to transporters in blood
what is an example of an integrated functional endocrine system
hypothalamus releases CRF which acts on cells of the anterior pituitary gland causing it to release ACTH which enters the blood stream and binds to the adrenal cortex leading to production and release of cortisol
how is specificity of hormone signalling achieved
- by chemical distinct hormones
- specific receptors for each hormones
- distinct distribution of receptors across target cells (localised)
every cell can be exposed to a hormone but only selective cells will respond - ones with the receptors
what are the 7 classical endocrine organs in the body
Pituitary gland thyroid gland parathyroid gland adrenal glands pancreas ovaries testis
what are the different types of hormone
modified amino acids
steroids
peptides
proteins
what is an example of a modified amino acid hormone
adrenaline
thyroid hormones
what is an example of steroid hormones
cortisone progesterone testosterone aldesterone -one
what is an example of peptide hormones
ACTH
ADH -anti-diuretic
oxytocin
-derived from larger precursor proteins
what is an example of a protein hormone
insulin
what is autocrine signalling
cell is signalling to itself
what is paracrine signalling
cell signals other cells close to it
what is endocrine signalling
cell signals travel via molecules transported by the BLOOD to target distant cells
what’s an example of overlap between different types of chemical signalling
somatostatin
paracrine in pancreas but endocrine in brain
how potent are hormones
vv potent as they exist at a very low concentration in the body
hormones can have an effect on multiple specific targets true/false
true
only one hormone can have an effect on a target true/false
false
multiple hormones can affect the same target
how is the biological response caused by a hormone initiated
active receptor engages in signal transduction cascade causing amplification of the original signal
the speed/onset/duration of hormone action variable true/fasle
true
seconds - days
how is hormone signalling terminated
by enzyme-mediated metabolic inactivation in the liver or at sites of action
what is the complementary action of hormones
when several hormones work together to produce the same effect
eg. adrenaline, cortisol and glucagon all contribute to the body in short term exercise
what is an antagonistic action of hormones
when hormones oppose each other
eg. insulin vs glucagon
what does insulin do
lowers plasma glucose level by stimulating glucose uptake into muscle and adipose tissue and inhibiting gluconeogenesis and glyconeogenesis
what does glucagon do
increased glucose level by stimulating glycogenolysis and and gluconeogenolysis but does not antagonise glucose uptake (adrenaline does)
when are amines released
in response to stimuli by Ca++ dependent exocytosis
how is adrenaline/amines stored
as a pre-synthesised hormone
what makes amines easy to transport around the body
its hydrophilic nature allows it to dissolve in blood
how are peptides and protein hormones stored
as presynthesied hormones formed from long precursor proteins
when are peptide and protein hormones released
in response to stimuli by Ca++ demented exocytosis
how are peptides transported in blood
freely due to hydrophilic nature
how are steroids stored
synthesised and released on demand
in order for cell to release a steroid hormone the signal must initiate synthesis
how are steroid hormones transported around the body
hydrophilic so 90% transported in plasma bound to proteins
only the 10% which is unbound which is biologically active - only this can cross the capillary role - rest is confined to the plasma
is steroid release quicker or slower than peptide hormone releases
slower as they need to be synthesised first
what do carrier transport proteins do
increase amount transported in blood
provide reservoir of hormone
extend half life of hormone in circulation
what are 3 important specific carrier proteins
cortisol-binding globulin
thyroxine-binding globulin
sex steroid-binding globulin
2 important general carrier proteins
albumin - binds many steroids and thyroxine
transthyretin - binds thyroxine and some steroids
how do carrier proteins help to maintain constant concentration of free lipophlillic hormone in blood
as the free hormone in the plasma is removed by crossing the capillary wall, it is replaced by hormone which is already bound to the carriers in blood
why is it only free hormone that can initiate biological response
because the carrier protein cant cross the capillary wall
what is the primary determinant of plasma concentration of hormone
the rate of secretion
what is the classic example of the control of secretion of hormone
HPA axis
cortisol negatively feed backs on the pituitary and hypothalamus glands
negative feedback maintains plasma concentration at a set level
how does the neuroendocrine system affect hormones
stress
elicits sudden burst in secretion in response to a specific stimulus
what is the general pattern of hormone secretion
diurnal (circadian) rhythm
secretion fluctuates as a function of time
how do u work out the plasma concentration of a hormone
it = the rate of secretion - rate of elimination
what is the most common routes of hormone elimination
local metabolism by liver
excretion by kidney
what are the 3 main types of hormone receptors
G-protein coupled receptors
Receptor Kinases
Nuclear receptors
what activates G-protein couples receptors
amines and some proteins. peptides
located at surface of cell bc these proteins are hydrophilic
what activates receptor kinases
proteins/ peptides
located at the surface of the cell bc these proteins are hydrophilic
where are the nuclear receptors found
inside the cell either in cytoplasm or nucleus
where are class 1 nuclear receptors found and what activated them
in the cytoplasm- bound to heat shock proteins - unbind and move to nucleus when activated
steroids activate them
where are class 2 nuclear receptors found what activated them
in the nucleus
activated by lipids
what activates hybrid class nuclear receptors
thyroid hormone
look at g-protein coupled receptor pathway
look at adrenaline pathway
angiotensin 2 pathway
what is an example of signalling via receptor kinases
the receptor for insulin
absence of insulin - no signalling
when insulin binds - beta subunits gain enzymatic activity by increase of tyrosine kinase activity- allows the receptor to phosphorylate itself - allows binding of insulin receptor substrate proteins which signals to protein kinase B producing metabolic effects
