Parasympathetic nervous system

Parasympathetic Nervous System

The Parasympathetic Nervous System (PNS) is one of the two main divisions of the Autonomic Nervous System (ANS). The other division is the Sympathetic Nervous System (SNS). The PNS is responsible for stimulating "rest-and-digest" or "feed and breed" activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion and defecation.

Anatomy

The parasympathetic nervous system primarily uses the neurotransmitter Acetylcholine (ACh) for its neural connections. The PNS consists of cranial nerves and sacral nerves. The cranial nerves are involved in the control of the eyes, mouth, facial expressions, and glands in the head, and other parts of the body. The sacral nerves control functions of the lower body.

Function

The main function of the PNS is to conserve energy and replenish the body's resources. It is responsible for the body's rest and digestion response when the body is relaxed, resting, or feeding. It basically undoes the work of sympathetic division after a stressful situation. The PNS reduces heart rate and blood pressure, stimulates the digestive system to process food and eliminate wastes, and restores the body to a state of calm and relaxation.

Clinical significance

Dysfunction of the parasympathetic nervous system can lead to many disorders. For example, a loss of parasympathetic innervation to the heart can lead to a condition known as tachycardia, which is a faster than normal heart rate at rest. Other conditions such as erectile dysfunction, constipation, and dry eyes can also occur due to dysfunction of the PNS.

See also

• Sympathetic Nervous System
• Autonomic Nervous System
• Nervous System

References

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