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Question: 1 / 400

What effect does the parasympathetic nervous system (PNS) have on heart rate?

Increases heart rate

Has no effect on heart rate

Slows heart rate

The parasympathetic nervous system (PNS) primarily functions to promote a state of rest and relaxation in the body, which includes the regulation of heart rate. Through the action of the vagus nerve, the PNS releases acetylcholine, which binds to receptors in the heart. This neurotransmitter has the effect of decreasing the heart rate by increasing the time it takes for the pacemaker cells in the sinoatrial (SA) node to depolarize. As a result, the PNS counterbalances the sympathetic nervous system, which tends to increase heart rate and promote a fight-or-flight response. Therefore, the slowing of the heart rate by the PNS is a key mechanism in maintaining homeostasis and allowing the body to conserve energy during restful states.

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Increases blood pressure

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