Autonomic nervous system（autonomic nervous system）It is a control system, which is largely adjusted unconsciouslyPhysical function, such as heart rate, digestion,Respiratory rate, pupillary reaction, urination,Sexual impulse。 The system mainly controls "stress" and "emergency" response.[1]
IIparasympathetic, divided into brain and spinal sacrum;Usually on the central axis of animal bodyCerebral ganglia、Nerve cordOr brain and spinal cord and their connecting components:
① The center of the brain is located in the brain stem, which is generally called the parasympathetic nucleus, and sends out fibers in the 3rd, 7th, 9th, and 10th pairsCerebral nerveInternal control and coordination of viscera, blood vessels, glands and other functions;
② The center of the sacrum, located in the middle lateral sacral nucleus in the gray matter of 2-4 segments of the sacral cordPreganglionic fibreTo the paraganglia of the organs near the organs and the internal ganglia of the organs within the walls of the organs, which form the pelvic nerve and innervateDescending colonThe followingAlimentary canal, pelvic organs andExternal genitalia。
Mechanism and innervation of autonomic nerve
Under normal circumstances, the sympathetic and parasympathetic nerves with opposite functions are in balance and restriction.In these twonervous systemWhen one side plays a positive role, the other side plays a negative role, which is very goodBalanced coordinationAnd control the physiological activities of the body, which is the function of autonomic nerves.Some people can also go throughyogaorBiofeedbackTechnology uses consciousness to regulate the function of its autonomic nervous system.
The main function of the sympathetic nerve is to dilate the pupils, accelerate the heartbeat, and shrink the skin and visceral blood vessels,coronary arteryDilation, blood pressure rise, smallBronchodilation, GastrointestinalDecreased peristalsis, bladder wallMuscle relaxation，Salivary secretionDecreased sweat gland secretionsweat、Pili erector muscleShrinkage, etc.When the body is in a state of nervous activity, sympathetic nerve activity plays a major role.
parasympatheticThe effect is opposite to that of sympathetic nerve, although it is inferior toSympathetic nervous systemThere is obvious consistency, but there is also considerable relationship.Its fibers are not distributed in the limbs, andadrenal gland, thyroid, uterus, etc. have parasympathetic nerve distribution.Parasympathetic nervous systemMainly when maintaining quietPhysiological needs, most play the role of recuperation.It has three functions:
① Pupils shrink to reduce irritation and promoteHepatic glycogenTo save energy.
② It causes the heart rate to slow down, blood pressure to decrease, and bronchi to shrink, so as to save unnecessary consumption.
③ The secretion of digestive gland increases, promotes the activity of gastrointestinal tract, promotes the excretion of urine and stool, and maintains the energy of the body.Assisting reproductive activities, such as reproductionVasodilation, bladder contraction and other reactions,Sexual organSecretory fluidIncrease.[2]
nervous system
Intestinal nervous systemCompared with the sympathetic and parasympathetic nerves, the enteric nervous system is less regulated by the central nervous system and more independent.Sympathetic and parasympathetic nerves generally act against each other (exception: salivary secretion).
Main differences
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Different central parts
The lower center of the sympathetic nerve is located at the first place of the spinal cordSternal segmentTo the thirdLumbar segmentThe lower level center of the parasympathetic nerve is located in the parasympathetic nucleus of the brain stem, the second sacral node to the fourth sacral node of the spinal cord, and the sacral parasympathetic nucleus.
Different parts of peripheral ganglia
The preganglionic fibers from the lateral horn of the sympathetic nervespinal nerveThe anterior root and spinal nerve come out togetherIntervertebral foramenAfter leaving the spinal nerveSympathetic trunkGanglia.Part is replaced in the sectionneuronAfter, itsPostganglionic fibreIt leaves the sympathetic trunk and returns to the spinal nerve, which is distributed to the limbs andbody wallBlood vesselsSweat glandandPili erector muscle。Most of the preganglionic fibersSympathetic trunkAfter replacing neurons, their postganglionic fibers no longer join the spinal nerves, but form around the arteriesPlexus, distributed along the artery to the head, neck, organs and glands in the thorax and abdomen.The preganglionic fibers from the parasympathetic nerve center are distributed in the parasympathetic ganglion exchange neurons, and the postganglionic fibers are distributed tosmooth muscleMyocardium, glands, and parasympathetic ganglia are generally near or within the walls of organs, with short postganglionic fibers.
Different effects on the same organ
Sympathetic excitationWhen the abdominal viscera andEndvasoconstriction, the heart rate is accelerated and strengthened;a bronchial tubeSmooth muscle dilation;Gastrointestinal motility and gastric secretion were inhibited;Hypermetabolism;Dilated pupils, etc.When the parasympathetic nerve is excited, the heart rate slows down and weakens;Bronchial smooth muscle contraction;Strengthening and promoting gastrointestinal movementDigestive juiceSecretion of;Pupil narrowing, etc.Generally, the visceral organs are doubly innervated by sympathetic and parasympathetic nerves. These two nerves usually resist the action of the same organ, but the activities of the two types of nerves are opposite, unified and coordinated in the whole.
The red part is sympathetic nerve, and the blue part is parasympathetic nerve
Sympathetic nerve activity is relatively extensive, and parasympathetic nerve activity is relatively limited. When the body is in a calm state, parasympathetic nerve excitation is dominant, which is beneficial toNutrientsThe digestion, absorption and energy supplement are conducive to protecting the body.WhenStrenuous exerciseOr in bad environment, the activity of sympathetic nerve is strengthened, and the potential of many organs in the body is mobilizedadaptabilityTo cope with the rapid changes in the environment and maintaininternal environmentIs relatively stable.
