What is A branch of the autonomic nervous system that decreases the heartbeat back to normal?

The branch of the autonomic nervous system that decreases the heartbeat back to normal is the parasympathetic nervous system. It primarily functions through the vagus nerve, which releases acetylcholine to slow the heart rate and promote a state of rest and relaxation. This counteracts the effects of the sympathetic nervous system, which increases heart rate during stress or danger. Overall, the parasympathetic system helps maintain homeostasis in the body.