PHSL232 Lecture Notes - Lecture 6: Muscarinic Acetylcholine Receptor M2, Vagus Nerve, Sympathetic Ganglion
Document Summary
Nervous and hormonal control of cardiac function by sympathetic stimulation. Sympathetic and parasympathetic action on excitation (sa node) and its intracellular signalling. Sympathetic action on excitation-contraction coupling (cardiomyocytes) and its intracellular signalling. Sympathetic action on contractility and frank starling curve. Extrinsic control of contraction by positive inotropic factors, such as glycosides. Noradrenaline: sympathetic nerve terminals: medulla sympathetic ganglion. Acetylcholine: released from parasympathetic nerve terminals (of the vagus nerve) Alter function without a primary change in edv. Effect of para/sympathetic nervous systems on the heart: Controlled by frequency of sa aps normally 100/min. Change in rate of sa node discharge through autonomic nervous activity. Unstable due to funny na channels: slow influx of na. Voltage operated ca channels open: ca influx. Makes membrane potential less negative: closer to threshold. Faster spontaneous depolarisation: increased slope of pre-potential: reaches threshold sooner. Spontaneous rate of sa node depolarisation is increased: heart rate increases- tachycardia.
