autonomic control of CVS Flashcards
What does the ANS control in the CVS?
Heart rate Force of contraction Resistance of blood vessels
What does the ANS control in the CVS?
- Heart rate
- force of contraction
- peripheral resistance of blood vessels
What is the parasympathetic input nerve to the heart?
What does it act on?
what GPCR is it?
what effect of inner action of this nerve does it have?
- Vagus nerve - 10th cranial nerve
- the SA node and AV node
- M2 GPCR (Gi)
- slows HR (negative chronotropic effect), decreases AV node conviction velocity to sloe HR further
What sympathetic input is there to the heart?
what does it act on?
what GPCR is used?
what is the effect of innervation?
- Post ganglion is fibres from sympathies trunk
- SA node, AV node and myocardium
- B1 receptors (noradrenaline) (Gs)
- positive chrontropic effect (inc HR), positive intropic effect (increase force of contraction)
Where does the parasympathiric and sympathetic control of the heart or originate from?
what are the affront inputs to this origination?
- Cardiovascular control centre in the Medulla oblongata
- baroreceptors (stretch receptors) in carotid sinus and aorta
What is teh sympathetic effect on the pacemaker potential in the SA node?
Shortens the time required to reach threshold
-noradrenaline acts on B1 receptors, B1 = Gs therefore when stimulated there is an increase in cAMP
more cAMP speeds up pacemaker potential
What is the parasympathetic effect on pacemaker potential?
Slows the time required to depolarise to threshold
it decreases the pacemaker slope
-ACh acts on M2 (Gi), therefore less cAMP is made mean inning less HCN channels are open
also Gi betagamma subunit acts on K+ channels and increases conductance
How does noradrenaline acting on B1 in the heart increases contraction?
B1= Gs = more cAMP
cAMP activates PKA
PKA phosphorylates L type Ca2+ channels in the sarcolemma and allows more Ca2+ in
it also increases Ca2+ uptake into the sarcoplasmic reticulum therefore has a bigger store of Ca2+ for consequent contractions
What type of innervation do all blood vessels receive?
what type do only some receive and give example?
- Sympathetic
- parasympathetic e.g. erectile vessels
What type of receptor do all vessels have for sympathetic innervation?
what type of receptor do only some have, give example?
- All have A1 (A little hole)
- some have B2 (skeletal muscle, liver, myocardium) - B = big hole
How does the sympathetic nervous system cause dilation and contraction of blood vessels?
There is a basal level of tone
less sympathetic input then this tone = dilation
more sympathetic input = constriction
What effect does adrenaline have on B2 receptors on blood vessels?
Adrenaline has a higher affinity for B2 than A1 in blood vessels
So at physiological conc B2 dilate the vessels
so dilation occurs
if adrenaline rises e.g. epipen - adrenaline will also bind to A1
How does binding to B2 cause vasodilation in blood vessels?
B2= Gs GPCR
this will produce cAMP and therefore activate PKA
PKA opens potasssium channels
PKA inhibits MLCK so cannot activate myosin light chain = no contraction = dilation
How does binding to A1 receptors in blood vessels cause vasoconstriction?
A1 = Gq GPCR
this produces IP3
IP3 causes more Ca2+ in the cell from SR = more contraction
Aldo DAG activate PKC
PKC inhibits MLCP therefore maintaining contraction = vasoconstriction
What is the role of local metabolites in blood vessels?
give example of local metabolites
They are important in vasodilation - more inmortant than B2
they ensure adequate perfusion of tissues
e.g. K+, H+, CO2
