Autonomic Control Of CVS Flashcards
Role of ANS.
Important for regulating many physiological functions: HR, BP, body temp. Exerts control over: smooth muscle, exocrine secretion, rate and force of contraction in the heart.
What do preganglionic neurones of both divisions release?
They both release acetylcholine, ACh acts on the nicotinic ACh receptors on the postganglionic cell.
What acts on adrenoreceptors and muscarinic receptors?
Noradrenaline and adrenaline act on adrenoreceptors, acetylcholine acts on muscarinic receptors.
Examples of adrenoreceptors and muscarinic receptors.
Adrenoreceptors: GPCRs, alpha and beta adrenoreceptors. Muscarinic: GPCRs, M1/2/3.
What does ANS control in CVS?
The ANS controls the heart rate, the force of contraction of the heart, the peripheral resistance to blood vessels.
Describe parasympathetic input to heart.
Preganglionic fibres synapse with postganglionic cells, these cells release ACh which acts on M2-receptors. This decreases the heart rate and decreases AV node conduction velocity.
Describe sympathetic input to heart.
Postganglionic fibres innervate SA node, AV node and myocardium. They act mainly on B1 adrenoreceptors: increases heart rate and increases force of contraction.
How does noradrenaline increases force of contraction?
Acts on B1 receptors in myocardium, this causes an increase in cAMP -> activates PKA. Phosphorylation of Ca2+ channels increases Ca2+ entry and increase uptake in the sarcoplasmic reticulum. This leads to an increased force of contraction.
Effect of B2 adrenoreceptors on vascular smooth muscle.
Causes vasodilation: increases cAMP -> PKA -> opens potassium channels and inhibits MLCK -> relaxation of smooth muscle.
Effects of a1 adrenoreceptors on vascular smooth muscle.
Causes vasoconstriction: stimulates IP3 production, increase in Ca2+ from stores and via influx of extracellular Ca2+ -> contraction of heart.
