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Autonomic Nervous System Editing file Lecture 4: AUTONOMIC NERVOUS SYSTEM • Red : important • Pink : in girls slides only • Blue : in male slides only • Green : notes, Extra Objectives At the end of the lecture, students should be able to: ❖ Define the autonomic nervous system. ❖ Describe the structure of autonomic nervous system ❖ Trace the preganglionic & postganglionic neurons in both sympathetic & parasympathetic nervous system. ❖ Enumerate in brief the main effects of sympathetic & parasympathetic system Autonomic Nervous System The autonomic nervous system is concerned with the Autonomic nervous system: Nerve cells innervation and control of Involuntary structures such as located in both central & visceral organs, smooth muscles, cardiac muscles and glands. peripheral nervous system Skeletal muscles are controlled by somatic motor Difference between somatic and visceral motor: ● Somatic motor ● Function: Maintaining the homeostasis Fibers from Anterior horn cell —-> to target of the internal environment along with ● Visceral motor Regulation: (Controlled) the endocrine system. 1-Brain: from nuclei by the Hypothalamus 2- spinal cord: lateral horn cell Note: Hypothalamus controls ﺗﻌدي ﻋﻠﻰ . Ganglion ﻗﺑل ﺗوﺻل ﻟﻠـ Location: Central nervous system and Target ● both of Autonomic system + peripheral nervous system Endocrine system. Autonomic Nervous System Unlike the somatic nervous system, the Efferent pathway of the autonomic nervous system is made up of Preganglionic Neuron two neurons called as: Preganglionic Postganglionic The cell bodies are The cell bodies are Postganglionic Neuron located in the brain located in the and spinal cord autonomic ganglia (inside CNS ). (outside CNS). Preganglionic axons synapse with the postganglionic neurons Note: before the fibers reach the target, it should first pass by the autonomic ganglion and synapse ( interconnection). Synapse: a junction between two nerve cells Based on the anatomical, physiological and pharmacological characteristics, the autonomic nervous system is divided into: Sympathetic Parasympathetic VS Activated during Concerned with exercise, excitement, conserving energy. and emergencies. “fight, flight, or fright” “rest and digest” Both divisions operate in conjunction with one another (have antagonistic control over the viscera) to maintain a stable internal environment For more understanding click here Sympathetic Parasympathetic Preganglionic neuron is in the Preganglionic neuron is in CNS. the CNS. The Preganglionic fiber(axon) The Preganglionic is shorter fiber(axon) is longer The Postganglionic neuron is The Postganglionic neuron is in the PNS and far from the in the PNS and close to the target target The Postganglionic The Postganglionic fiber(axon) is shorter fiber(axon) is longer Target organ Target organ Note438: The cause of preganglionic (White) and postganglionic (Grey) fibers having different colors is the Myelin sheath that the preganglionic fibers (white) are sheeted with. Myelin helps isolate preganglionic (ﺗﺧﻠﯾﮫ ﻣﻌزول اﻛﺛر وﯾوﺻل اﺳرع) .fibers for faster transportation Sympathetic Nervous System Postganglionic fiber Preganglionic fiber L2 Sympathetic Division 1- Preganglionic Neurons: 2- Postganglionic ganglia: Located nearer the central nervous system as: located in the lateral gray horn of T1-L2 segments of spinal cord Prevertebral is the celiac and mesenteric (ThoracoLumbar outflow) In front of vertebral column Paravertebral forming sympathetic chain Next to,Parallel IMPORTANT NOTE(438): Sympathetic neurons only found in spinal cord NOTE: as their preganglionic neurons are short, their ganglia (POSTGANGLIONIC NEURONS) are located near to the CNS (spinal cord). NOTE: Outflow means the passage of impulses outwardly from the central nervous system. Postganglionic ganglia Paravertebral Ganglia They are interconnected to form 2 sympathetic chains, one on each side of vertebral column. 3 in Cervical part of chain Number of ganglia: 11-12 in Thoracic part 4 in Lumbar & Sacral parts each The chains end into a common “ganglion impar” in front of coccyx. Preganglionic Fibers Within the sympathetic chain, these fibers may: ● Run in the ventral roots of 1- ascend : to move upward. 4- leave the sympathetic chain the spinal nerve. 2- descend : to move (without synapse) to reach downward. coeliac & mesenteric ganglia ● Travel through the spinal nerve, and then join the 3- remain at the same level Preganglionic fibers sympathetic chain via the to synapse with neurons surrounded by (around White Rami Communicans. (postganglionic) of branches of abdominal aorta) (WRC). paravertebral ganglia located to synapse with their neurons *Between nerve and ganglion in sympathetic chain. (postganglionic). *white ramus Preganglionic fibers = before rely Postganglionic fibers 1-Fibers from the sympathetic chain: Enter again into the spinal nerve through (Grey Rami Communicants), to supply structure in head, thorax + blood vessels and sweat glands. 2- Fibers from the cells of coeliac, mesenteric(superior & inferior): supply abdominal and pelvic viscera Parasympathetic division Cranial flow Sacral flow Preganglionic Nuclei of the 3rd, 7th, 9th & 10th The lateral gray horn of cranial nerves, in the brain stem S2-S4 segments of spinal neuron (Cranial outflow) cord (Sacral outflow) carried by 3rd, 7th, 9th & 10th Are carried by pelvic Preganglionic cranial nerves and terminate in splanchnic nerves to ciliary, pterygopalatine, peripheral ganglia in pelvis fiber (axon) submandibular, otic & peripheral where they synapse. ganglia ciliary pterygopalatine, peripheral ganglia in pelvis Postganglionic Postganglionic submandibular, otic & peripheral ganglia. neuron Postganglionic axons innervate innervate organs of the Postganglionic (supply) organs of the: fiber(axon) pelvis and lower abdomen head, neck, thorax, and abdomen fiber (axon) Structure Sympathetic effect Parasympathetic effect pupil Constricts pupil (ﺗﺗوﺳﻊ) Iris of the eye(pupils) Dilates Ciliary muscle of the eye Relaxes Contracts Salivary glands Reduces secretion Increases secretion Reduces secretion Increases secretion (اﻟﻐده اﻟدﻣﻌﯾﺔ) Lacrimal gland Heart Increases rate and force of contraction Decreases rate and force of contraction Dilates Constricts (اﻟﺷﻌب اﻟﮭواﺋﯾﺔ) Bronchi Gastrointestinal tract Decreases motility Increases motility Sweat glands Increases secretion ------------------- Erector pili muscles (attached to hair follicles) Contracts ------------------- MCQs Q1) Preganglionic fibers of the sacral outflow are carried by: A) Ciliary ganglion B) Submandibular ganglion C) Pelvic splanchnic nerves D) Peripheral ganglion Q2) Post ganglionic neurons syanpse with: A) Preganglionic neuron B) Target organs C) Postganglionic fibers D) Preganglionic fibers Q3) The cell bodies of preganglionic neurons are located in A) Spinal cord B) Brain C) Peripheral nervous system. D) A and B Q4) Autonomic nervous system is requlated by: A) Pineal gland B) Diencephalon C) Hypothalamus D) Thymus gland Q5) The parasympathetic division is activated during: A) Exercise B) Fear C) Conserving energy. D) Excitement Q6) Which of the following is a parasympathetic effect: A)Decreased secretion of lacrimal gland B) Constriction of the ciliary muscle of the eye C) Dilated iris of the eye D) Dilated bronchi 1-C 2-B 3-D 4-C 5-C 6-B 5-C 4-C 3-D 2-B 1-C Team members: Team leaders: Contact us: [email protected].
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