what is parasympathetic nervous system?❣
Answers
Answer:
The parasympathetic nervous system predominates in quiet “rest and digest” conditions while the sympathetic nervous system drives the “fight or flight” response in stressful situations. The main purpose of the PNS is to conserve energy to be used later and to regulate bodily functions like digestion and urination.
★ Parasympathetic nervous system
- or (Parasympathetic Division) is the autonomic nervous system is the main part of the, from the bottom of the midbrain , pons , medulla and spinal cord sacral. Its preganglionic fibers exchange neurons in the parasympathetic ganglion , which then sends out the postganglionic fibers to smooth muscle , myocardium and glands . Usually located parasympathetic ganglia organ within the organ or the vicinity of the wall.
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★ Vegetative nerve concept
In the 19th century, German scholar Lyle first proposed the term " vegetative nervous system ". Later British scientist Langley divided the autonomic nervous system into two parts : sympathetic and parasympathetic. The vegetative nervous system is not subject to consciousness, but it can be adjusted to a certain extent after training. The activity of the autonomic nervous system is closely related to emotions .
In the past, autonomic nerves were also called " autonomic nerves ". Meaning, they are not controlled by the central nervous system , so people cannot control the activities of the internal organs at will. However, biofeedback research shows that people can control the activities of internal organs to a certain extent through special training, such as regulating the rise and fall of body temperature, the level of blood pressure, and the speed of heartbeat. Therefore, it is inaccurate to call the autonomic nerve "autonomic nerve".
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★ Medical classification
The autonomic nervous system is divided into two parts : sympathetic nerve and parasympathetic nerve. The sympathetic nervous system emanates from the entire thoracic spinal cord of the spinal cord and the gray matter lateral corners of the upper three lumbar spinal cords . It uses short communication branches (pre-node fibers) to connect with the sympathetic trunk on both sides of the spinal cord, and then the sympathetic trunk nerves send out post-ganglia fibers to control the activities of organs and blood vessels in the chest and abdomen. The parasympathetic nervous system originates from the sacrum of the midbrain, pons, medulla oblongata, and spinal cord. Its preganglionic fibers exchange neurons in the parasympathetic ganglion, which then sends out the postganglionic fibers to smooth muscle, myocardium, and glands. The parasympathetic ganglion is generally located near the organ or in the organ wall.
In the sympathetic nervous system , most of the preganglionic fibers are very short, and the synapses constitute the sympathetic nerve chain, which is located on the side of the spinal cord. The post-ganglionic fibers emitted from here reach the target organs such as heart, lungs and stomach. In the parasympathetic nervous system, the preganglionic fibers with myelin sheath are very long, and there is no synaptic connection with the sympathetic chain , and its short postganglionic fibers are connected with the synapse. When sympathetic nerve activity is strengthened, the heartbeat is accelerated, cardiac output increases, blood pressure increases, the arteries in the large muscles expand, the adrenal medulla accelerates the secretion of epinephrine, the blood sugar level rises, and the body's energy is mobilized to "or fight or escape" Be prepared; when parasympathetic activity increases, cardiovascular function weakens, heart rate slows, blood flow to the whole body decreases, and blood supply to the stomach and intestines increases, blood sugar is stored in the liver in the form of glucose, and metabolism slows down. Energy storage. The former is called catabolism and the latter is called anabolic . The sympathetic nervous system and the parasympathetic nervous system generally antagonize each other, but work together.
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★ Function
The sympathetic and parasympathetic nerves are functionally antagonistic . Generally speaking, people regard the sympathetic nerve as the body's emergency response mechanism. When people struggle, wrestle, fear, and anger, the sympathetic nerves act immediately, which accelerates the heart's beating; it orders the liver to release more blood sugar so that the muscles can be used; temporarily slow down or stop the activity of the digestive organs, thereby mobilizing the whole body Coping with crisis. The role of the parasympathetic nerve is the opposite. It plays a balancing role, inhibits excessive excitement of various organs in the body, and enables them to obtain the necessary rest.
The parasympathetic nervous system can maintain the physiological balance of the body in a quiet state , and its role has three aspects:
- ①Promote gastrointestinal activity, secretion of digestive glands , promote the excretion of urine, and maintain energy of the body.
- ②Pupillary diminishes to reduce stimulation, promote liver glycogen production, and save energy.
- ③Slow heartbeat, blood pressure, and bronchial tubes to reduce unnecessary consumption, assist in reproductive activities, such as dilated reproductive blood vessels, increased secretion of sexual organs .