AUTONOMIC NERVOUS SYSTEM PARA SYMPATHETIC amp SYMPATHETIC NERVOUS SYSTEM MOLECULAR MYSTERIES

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#trending #viralvideo #youtubeshorts #nervoussystem #neuron #parasympatheticnervoussystem #sympatheticnervoussystem #involuntary • AUTONOMIC NERVOUS SYSTEM || PARA SYMPATHETIC SYMPATHETIC NERVOUS SYSTEM || MOLECULAR MYSTERIES • The autonomic nervous system is a component of the peripheral nervous system that regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal. It contains three anatomically distinct divisions: sympathetic, parasympathetic, and enteric. • The sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS) contain both afferent and efferent fibers that provide sensory input and motor output, respectively, to the central nervous system (CNS). Generally, the SNS and PNS motor pathways consist of a two-neuron series: a preganglionic neuron with a cell body in the CNS and a postganglionic neuron with a cell body in the periphery that innervates target tissues. The enteric nervous system (ENS) is an extensive, web-like structure that is capable of function independently of the remainder of the nervous system.It contains over 100 million neurons of over 15 morphologies, greater than the sum of all other peripheral ganglia, and is chiefly responsible for the regulation of digestive processes. • Activation of the SNS leads to a state of overall elevated activity and attention: the “fight or flight” response. In this process, blood pressure and heart rate increase, glycogenolysis ensues, gastrointestinal peristalsis ceases, etc. The SNS innervates nearly every living tissue in the body. The PNS promotes the “rest and digest” processes; heart rate and blood pressure lower, gastrointestinal peristalsis/digestion restarts, etc. The PNS innervates only the head, viscera, and external genitalia, notably vacant in much of the musculoskeletal system and skin, making it significantly smaller than the SNS. The ENS is composed of reflex pathways that control the digestive functions of muscle contraction/relaxation, secretion/absorption, and blood flow. • Presynaptic neurons of both the SNS and PNS utilize acetylcholine (ACh) as their neurotransmitter. Postsynaptic sympathetic neurons generally produce norepinephrine (NE) as their effector transmitter to act upon target tissues, while postsynaptic parasympathetic neurons use ACh throughout. Enteric neurons have been known to use several major neurotransmitters such as ACh, nitrous oxide, and serotonin, to name a few. • Structure and Function • Sympathetic Nervous System • Sympathetic neurons have cell bodies located in the intermediolateral columns, or lateral horns, of the spinal cord. The presynaptic fibers exit the spinal cord through anterior roots and enter the anterior rami of T1-L2 spinal nerves and onto the sympathetic trunks via white rami communicantes. From here, the fibers may ascend or descend the sympathetic trunk to a superior or inferior paravertebral ganglion, respectively, pass to adjacent anterior spinal nerve rami via gray rami communicantes, or cross through the trunk without synapsing and continue through an abdominopelvic splanchnic nerve to reach prevertebral ganglia. Because of the central location of the sympathetic ganglia, presynaptic fibers tend to be shorter than their postsynaptic counterparts. • Parasympathetic Nervous System • Parasympathetic fibers exit the CNS via cranial nerves (CN) III, VII, IX, and X, as well as through the S2-4 nerve roots. There are four pairs of parasympathetic ganglia, and they are all located in the head. CN III, via the ciliary ganglion, innervates the iris and ciliary muscles of the eye. CN VII innervates the lacrimal, nasal, palatine, and pharyngeal glands via the pterygopalatine ganglion, as well as the sublingual and submandibular glands via the submandibular ganglion. CN IX innervates the parotid glands via the otic ganglion. Every other presynaptic parasympathetic fiber synapses in a ganglion near or on the wall of the target tissue; this leads to the presynaptic fibers being significantly longer than the postsynaptic. The location of these ganglia gives the PNS its name: “para-” means adjacent to, hence, “parasympathetic.” • The vagus nerve, CN X, makes up about 75% of the PNS and provides parasympathetic input to most of the thoracic and abdominal viscera, with the sacral parasympathetic fibers innervating the descending and sigmoid colon and rectum. The vagus nerve has four cell bodies in the medulla oblongata. • Thanks for watching • Subscribe, Like and Share your ideas • Parinita

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