How do the sympathetic and parasympathetic nervous system affect cardiac output?
What will be an ideal response?
Answer: The parasympathetic nervous system releases acetylcholine on the pacemaker cells, increasing potassium permeability, hyperpolarizing the cells, and slowing heart rate (which reduces cardiac output). The sympathetic nervous system also innervates the pacemaker cells, secreting norepinephrine on the pacemaker cells, activating beta receptors, increasing sodium permeability, causing faster depolarization, higher heart rate, and greater cardiac output. An increase in circulating epinephrine from activation of the sympathetic nervous system will increase heart rate in the same way. Sympathetic neurons also innervate much of the myocardium, and their activation increases the strength of heart contraction (contractility) and stroke volume. This occurs because activation of adrenergic receptors increases cAMP and protein kinase activities in the muscle cells, increasing calcium levels in the cytoplasm and bound to troponin.`
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What will be an ideal response?
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