adrenoceptors Flashcards
what is a signalling pathway
an intracellular biochemical pathway which links the receptor to the cellular outcomes
do receptors share signalling pathways
yes
how can one receptor control many functions from one second messenger
pathways diverge as they cascade down
how does a GPCR transduce signals
it links to one or more G-protein to transduce the receptor signal to an effector enzyme/target
what does calcium binding mean
contraction in a smooth muscle environment
what does increase in cAMP lead to (b1 in heart)
an increase in protein kinases which increases calcium coming into cell
causes contraction
what do GS proteins do in airway vessels (b2)
stimulates production of cAMP which inhibits calcium release.
leads to smooth muscle relaxation
can the same signalling pathway have different effects
yes, depending on the needs of the cell type
characteristics of a1 adrenoceptors
close to NA release site
activated by neuronal and circulating NA
characteristics of a2 adrenoceptors
distant from NA release site
activated by circulating NA
negative feedback control of a2 adrenoceptors
agonist binds to the a2 sympathetic nerve site
decrease in calcium in and out of the cell
dropping calcium inhibits release of noradrenaline from N terminus
what is the functional outcome of the cell dependent on
the signalling activated by the receptor
the cell type and cellular machinery downstream of the signalling system in that cell
what do selective A1 adrenoceptor antagonists do
decrease vasoconstriction tone (PVR)
no change in HR or CO during chronic use
examples of selective A1 adrenoceptor antagonists
prazosin
doxazosin
what does activation of the b1 receptor do in heart
increase force of myocardial infraction
increase rate of contraction
excess stimulation leads to arrhythmia
examples of b1 antagonists
atenolol, metoprolol etc
examples of b2 antagonists
butoxamine
what does b1 activation do in gi tract
relaxation of smooth muscle
what does b1 activation do in fat
lipolysis
triglyceride fat stores to fatty acids
b1 activation in kidney
renin release
all synthesised increases BP
what does less excretion from kidneys lead to
more retention of water and sodium which raises blood pressure
what do b1 activation do in kidney
they cause renin release which causes angiotensin I and II release
this increases aldosterone release which decreases water and sodium excretion in kidneys
what happens when b1 is blocked in kidney
the opposite of what usually happens when b1 isn’t blocked
leads to decreased blood volume which leads to decreased blood pressure
