What Is the Parasympathetic Nervous System?

Parasympathetic Division (Parasympathetic Division) is the main part of the autonomic nervous system, originating from the midbrain, pontine, medulla, and the sacral spinal cord. Its preganglionic fibers exchange neurons in the parasympathetic ganglia, and from this it sends out postganglionic fibers to the smooth muscle, heart muscle, and glands. Parasympathetic ganglia are generally located near or in the wall of the organ. ^[1]

19th Century German Scholar

Map of sympathetic and parasympathetic nerves ^[3]

Sympathetic and parasympathetic nerves have antagonistic properties. Generally speaking, people regard sympathetic nerves as the body's mechanism for emergency situations. When people struggle, struggle, fear, and anger, the sympathetic nerves work immediately, which accelerates the heart's beating; orders the liver to release more blood sugar, so that muscles can be used; temporarily slows or stops the activities of the digestive organs, thereby mobilizing the body's strength to Coping with critical situations. The parasympathetic nerve has the opposite effect. It plays a balancing role, inhibits the excessive excitement of various organs in the body, and gives them the necessary rest. ^[1]

The parasympathetic nervous system can maintain the physiological balance of the body in a quiet state, and its role has three aspects:

Promote gastrointestinal activity, secretion of digestive glands, promote the excretion of feces, and maintain the energy of the body.

Pupil diminishes to reduce irritation, promote liver glycogen production, and save energy.

The heartbeat slows down, blood pressure decreases, and bronchus shrinks to save unnecessary consumption and assist in reproductive activities, such as expanding the reproductive blood vessels and increasing the secretion of the sexual organs.