Parasympathetic nervous system

autonomic nervous system

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Parasympathetic Division is autonomic nervous system The main part of, from midbrain 、 Pons 、 Medulla oblongata and spinal cord Sacrum. its Preganglionic fibre Exchange in parasympathetic ganglia neuron , and then sent from here Postganglionic fibre , to smooth muscle 、 myocardium and Glands 。 Parasympathetic ganglia are generally located in viscera Nearby or in the organ wall.^[1]

Chinese name: Parasympathetic nervous system
Foreign name: parasympathetic nervous system
Nature: Main part of vegetative nervous system

Function: Inhibit the overexcitement of various organs in the body
Subordination: autonomic nervous system
Presenter: Lyle, Germany, Langley, England

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Concept of autonomic nerve

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German scholars in the 19th century Lyle First proposed“ autonomic nervous system ”This noun. Later, British scientist Langley will autonomic nervous system Divided into sympathetic nerve And parasympathetic nerve. autonomic nervous system Not controlled by consciousness, but can be adjusted to a certain extent after training. autonomic nervous system Activities and emotion They have close relations.^[1]

Vegetative nerve It used to be called“ autonomic nerve ”。 It means they don't central nervous system So people can't control it at will Viscera Activities of. However, the research of biofeedback shows that people can control the activities of internal organs at will to a certain extent through special training, such as regulating the rise and fall of body temperature, blood pressure, and heartbeat speed. Therefore, it is not accurate to call vegetative nerves "autonomic nerves".^[1]

Medical classification

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autonomic nervous system Divided into sympathetic nerve And parasympathetic nerve. Sympathetic nervous system from spinal cord All of the thoracic spinal cord and the gray matter of the upper three lumbar spinal cord issued from the lateral horn. It relies on a short traffic support（ Preganglionic fibre ）It is connected to the sympathetic trunk on both sides of the spinal cord, and then sent out by the sympathetic trunk nerve Postganglionic fibre To control the activities of viscera and blood vessels in the chest and abdomen. The parasympathetic nervous system originates from the midbrain, pons, medulla and the sacrum of the spinal cord. Its preganglionic fibers exchange neurons in the parasympathetic ganglia, from which they send out postganglionic fibers to smooth muscle, myocardium and glands. The parasympathetic ganglia are generally located near or in the walls of the organs.^[1]

Sympathetic nervous system Most of the preganglionic fibers are very short, and the synapses form the sympathetic nerve chain, which is located on the side of the spinal cord. From here, the postganglionic fibers reach the heart, lungs, stomach and other target organs. In the parasympathetic nervous system, the myelinated preganglionic fibers are very long and have no relationship with the sympathetic chain Synapse Its short postganglionic fibers are associated with synapses. sympathetic nerve When the activity is strengthened, the heart rate increases, the cardiac output increases, the blood pressure increases, the arteries in the big muscles expand, the adrenal medulla accelerates the secretion of adrenaline, the blood sugar level increases, mobilize the body's energy, and prepare for the "fight or flight response"; When the activity of parasympathetic nerve is strengthened, the cardiovascular function is weakened, the heart rate is slowed down, and the blood flow to the whole body is reduced, while the blood supply to the stomach and intestines is increased. The blood sugar is stored in the liver in the form of glucose, and the metabolism is slowed down, and the energy is stored. The former is called Catabolism , the latter is called Anabolism 。 Generally, the sympathetic nervous system and the parasympathetic nervous system are antagonistic to each other, but they work together.^[2]

Functional function

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Action diagram of sympathetic and parasympathetic nerves^[3]

The sympathetic and parasympathetic nerves are functionally Antagonism nature. Generally speaking, people regard the sympathetic nerve as the body's mechanism to deal with emergencies. When people struggle, struggle, fear and anger, sympathetic nerve It works immediately, accelerating the beating of the heart; Order the liver to release more blood sugar, so that muscles can use it; Temporarily slow down or stop the activities of digestive organs, so as to mobilize the whole body to deal with emergencies. On the contrary, the parasympathetic nerve plays a balancing role, inhibiting the overexcitement of various organs in the body and enabling them to obtain necessary rest.^[1]

The parasympathetic nervous system can keep the body in a quiet state Physiological balance , which has three functions:

① Improve gastrointestinal activity, Digestive gland It can promote the excretion of urine and urine, and maintain the energy of the body.

② Pupils shrink to reduce irritation and promote Hepatic glycogen To save energy.

③ Heart rate slows down, blood pressure drops and bronchi shrink to save unnecessary consumption and assist reproductive activities, such as expanding reproductive vessels and sexual organs Secretory fluid Increase.

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