BIO 3302 Lecture Notes - Lecture 3: Cardiac Output, Viscosity, Capillary
16 Nov 2016
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Document Summary
Ecg is a representation of all the electrical activity in the cells of a heart that you can measure in the extracellular fluid in the body. You need to speed up or slow down heart to meet physiological demands of the animal that has that heart; this come back to the pacemaker cells that initiate the heartbeat. The sa node (i. e. the heart"s pa(cid:272)e(cid:373)aker it contains the pacemaker cells with the fastest rate of depolarization) is innervated by the autonomic nervous system (both sympathetic and parasympathetic nervous systems) The sa node contains beta-1 receptors that are activated by noradrenaline released from sympathetic nerves and m2 muscarinic receptors that are activated by acetylcholine released from parasympathetic nerves. Too add the effects of sympathetic and parasympathetic stimulation in the pacemaker potential graph: The pacemaker potential is the only thing that changes: steeper vs shallow slope. Negative chronotropic effect = slowing down the heart (parasympathetic stimulation)
