Understanding Electrical Stimulation in the Heart - AP Biology

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Question

The sinoatrial node generates action potentials at a faster pace than normal heart rate. Why does the heart beat more slowly than the SA node would dictate?

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Answer

The vagus nerve is responsible for slowing down the heart rate, and is able to "override" the faster, natural pace of the sinoatrial node. When the vagus nerve is severed from the heart, the heart will pump at the pace of the SA node.

Note that innervation is not necessary for the heart to continue beating; it is self-sustaining, but can be affected by innervation from the vagus nerve.

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