Certified Emergency Nurse (CEN) Practice Test

The parasympathetic nervous system is responsible for decreasing heart rate and respiratory rate. This system is part of the autonomic nervous system and functions primarily to promote a "rest and digest" state. When activated, it releases neurotransmitters like acetylcholine, which acts on the heart to decrease its rate of contraction and slows down the respiratory rate by reducing the activity of the respiratory muscles. This response is crucial during times of relaxation or recovery, helping to conserve energy and restore the body to a state of calm after stress or activity.

In contrast, the sympathetic nervous system is more associated with the "fight or flight" response, which increases heart and respiratory rates to prepare the body for immediate action. The central nervous system, although vital in processing and regulating numerous functions of the body, does not directly control the decrease of these rates. The somatic nervous system primarily controls voluntary muscle movements and does not influence heart and respiratory rates directly. Therefore, the parasympathetic nervous system’s specific role in decreasing heart and respiratory rates clearly supports its selection as the correct answer.