Cardiovascular SystemChronotropic Effects of the Autonomic Nervous System*The nervous system only modulates the heart beat but does not initiate it.*cardiac center of the medulla consist of two neuronal pools*cardioacceleratory center-sends signals by way of the sympathetic cardiac accelerator nerves to the SA node, AV node, and myocardium.*These nerves secrete norepinephrine, which bind to B-adrenergic receptors that tend to increase heart rate and contractilityChronotropic Effects of the Autonomic Nervous System*Cardioinhibitory center- sends signals by way of the parasympathetic fibers in the vagus nerves to the SA and the AV nodes]*the right vagus innervates mainly the SA node and the left vagus, the AV node*nerve secretes acetylcholine which binds to muscarinic receptors to opens K+ channels (K+ leaves the cell) to hyperpolarize the cell which causes the cell to fire less frequently, thereby slowing the heart rate.
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