Notice in the picture on the left that the sympathetic nervous system originates in the spinal cord. Specifically, the cell bodies of the first neuron (the preganglionic neuron) are located in the thoracic and lumbar spinal cord. Axons from these neurons project to a chain of ganglia located near the spinal cord. In most cases, this neuron makes a synapse with another neuron (post-ganglionic neuron) in the ganglion. A few preganglionic neurons go to other ganglia outside of the sympathetic chain and synapse there. The post-ganglionic neuron then projects to the "target" - either a muscle or a gland. Show Two more facts about the sympathetic nervous system: the synapse in the sympathetic ganglion uses acetylcholine as a neurotransmitter; the synapse of the post-ganglionic neuron with the target organ uses the neurotransmitter called norepinephrine. (Of course, there is one exception: the sympathetic post-ganglionic neuron that terminates on the sweat glands uses acetylcholine.) The Parasympathetic Nervous System It is a nice, sunny day...you are taking a nice walk in the park. Notice in the picture on the left, that the cell bodies of the parasympathetic nervous system are located in the spinal cord (sacral region) and in the medulla. In the medulla, the cranial nerves III, VII, IX and X form the preganglionic parasympathetic fibers. The preganglionic fiber from the medulla or spinal cord projects to ganglia very close to the target organ and makes a synapse. This synapse uses the neurotransmitter called acetylcholine. From this ganglion, the post-ganglionic neuron projects to the target organ and uses acetylcholine again at its terminal. Autonomic Nervous System StructureSympathetic StimulationParasympathetic StimulationIris (eye muscle)Pupil dilationPupil constrictionSalivary GlandsSaliva production reducedSaliva production increasedOral/Nasal MucosaMucus production reducedMucus production increasedHeartHeart rate and force increasedHeart rate and force decreasedLungBronchial muscle relaxedBronchial muscle contractedStomachPeristalsis reducedGastric juice secreted; motility increasedSmall IntestineMotility reducedDigestion increasedLarge IntestineMotility reducedSecretions and motility increasedLiverIncreased conversion ofglycogen to glucose epinephrine secreted Sphincter closedWall contracted Sphincter relaxed It should be noted that the autonomic nervous system is always working. It is NOT only active during "fight or flight" or "rest and digest" situations. Rather, the autonomic nervous system acts to maintain normal internal functions and works with the somatic nervous system. The enteric nervous system is a third division of the autonomic nervous system that you do not hear much about. The enteric nervous system is a meshwork of nerve fibers that innervate the viscera (gastrointestinal tract, pancreas, and gall bladder). While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Select Citation Style Copy CitationShare Share Share to social media Facebook Twitter URL https://www.britannica.com/science/autonomic-nervous-systemGive Feedback External Websites Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Your Feedback Submit FeedbackThank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article. External Websites
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Alternate titles: ANS, vegetative nervous system, visceral nervous system By The Editors of Encyclopaedia Britannica Last Updated: Nov 18, 2022 Article History Table of Contentsautonomic nervous system See all media Key People:Walter Rudolf Hess...(Show more)Related Topics:sympathetic nervous system digestive nerve plexus parasympathetic nervous system vasomotor system enteric nervous system...(Show more) See all related content → Summary Read a brief summary of this topicautonomic nervous system, in vertebrates, the part of the nervous system that controls and regulates the internal organs without any conscious recognition or effort by the organism. The autonomic nervous system comprises two antagonistic sets of nerves, the sympathetic and parasympathetic nervous systems. The sympathetic nervous system connects the internal organs to the brain by spinal nerves. When stimulated, these nerves prepare the organism for stress by increasing the heart rate, increasing blood flow to the muscles, and decreasing blood flow to the skin. The nerve fibres of the parasympathetic nervous system are the cranial nerves, primarily the vagus nerve, and the lumbar spinal nerves. When stimulated, these nerves increase digestive secretions and reduce the heartbeat. What are the 3 nervous system functions?First, the basic functions of the nervous system are sensation, integration, and response.
What are the 3 subsystems of the autonomic nervous system?The ANS can be divided by subsystems into the Parasympathetic Nervous System (PSNS), Sympathetic Nervous System (SNS), and Enteric Nervous System (ENS).
What are the functions of the autonomic nervous system quizlet?What is the function of the autonomic nervous system? a control system that acts largely unconsciously and regulates bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.
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