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The Nervous System Peripheral Nerve Regeneration

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The Nervous System Peripheral Nerve Regeneration 1/18/2016 Peripheral Nerve Regeneration • Possible if cell body has not been damaged • Axon underlying myelin sheath can regenerate The Nervous System PNS continued Endoneurium Schwann cells 1 The axon 2 Macrophages Schwann cell Macrophage Droplets becomes clean out the of myelin fragmented at dead axon distal the injury site. to the injury. Fragmented axon Site of nerve damage Figure 13.4 (1 of 4) Figure 13.4 (2 of 4) Aligning Schwann cells 3 Axon sprouts, Schwann cell Site of new 4 The axon form regeneration tube or filaments, myelin sheath regenerates and grow through a formation a new myelin regeneration tube sheath forms. formed by Schwann cells. Fine axon sprouts Single enlarging or filaments axon filament Figure 13.4 (3 of 4) Figure 13.4 (4 of 4) 1 1/18/2016 Neuritis Shingles • Inflammation of a nerve • Varicella Zoster virus – Sciatica • Dorsal root ganglia – Bell’s Palsy • Consistent with dermatome • Vaccine Multiple Sclerosis • Loss of myelin in CNS scleroses Central nervous system (CNS) Peripheral nervous system (PNS) – Visual disturbances Muscle weakness Sensory (afferent) Motor (efferent) division – division • Autoimmune disorder Somatic nervous Autonomic nervous system system (ANS) • Remissions Sympathetic Parasympathetic • Progressive division division Figure 14.1 Autonomic Nervous System (ANS) Structure of the ANS • Involuntary Sensory (afferent) pathway • Sensory (afferent) pathways Visceral interoceptors (visceroceptors) • Motor (efferent) pathways ° Osmolarity ° Pressure • Visceral reflex system ° Temperature ° Blood gases ° Chemical composition of plasma and body fluids 2 1/18/2016 Structure of the ANS Dorsal root (sensory) Dorsal root ganglion Dorsal horn (interneurons) Somatic • Sensory (afferent) pathway sensory – Single sensory neuron from organ to CNS neuron Visceral • Cell body in dorsal root ganglion sensory • Synapse with association neurons in spinal cord neuron Visceral motor Spinal nerve neuron Ventral horn Ventral root (motor neurons) Somatic (motor) motor neuron Interneurons receiving input from somatic sensory neurons Interneurons receiving input from visceral sensory neurons Visceral motor (autonomic) neurons Somatic motor neurons Figure 12.32 Autonomic Nervous System (ANS) Autonomic Nervous System (ANS) • ANS Motor (efferent) neurons • Efferent (motor) pathway – Innervate smooth muscle, cardiac muscle and – Two motor neurons between CNS and effector glands • Preganglionic neuron – Operate via subconscious control – Cell body in CNS • Postganglionic neuron – Cell body in autonomic ganglion (outside CNS) Motor Pathways Neuro- Autonomic Nervous System (ANS) Cell bodies in central transmitter Effector nervous system Peripheral nervous system at effector organs Effect Single neuron from CNS to effector organs ACh + • Visceral reflex system Stimulatory SYSTEM Heavily myelinated axon SOMATIC NERVOUS Skeletal muscle – E.g., coughing, sneezing, swallowing, vomitting Two-neuron chain from CNS to effector organs ACh NE Unmyelinated postganglionic axon Lightly myelinated Ganglion Epinephrine and preganglionic axons norepinephrine + ACh SYMPATHETIC Stimulatory or inhibitory, depending Adrenal medulla Blood vessel on neuro- transmitter and ACh ACh Smooth muscle receptors (e.g., in gut), on effector AUTONOMIC NERVOUS SYSTEM NERVOUS AUTONOMIC organs Lightly myelinated Unmyelinated glands, cardiac preganglionic axon Ganglion postganglionic muscle axon PARASYMPATHETIC Acetylcholine (ACh) Norepinephrine (NE) Figure 14.2 3 1/18/2016 Stimulus 1 Sensory receptor Dorsal root ganglion in viscera 2 Visceral sensory Spinal cord Central nervous system (CNS) Peripheral nervous system (PNS) neuron 3 Integration center Sensory (afferent) Motor (efferent) division division Spinal cord grey matter Within gastrointestinal tract wall Somatic nervous Autonomic nervous system system (ANS) Autonomic ganglion Efferent pathway 4 Sympathetic Parasympathetic (two-neuron chain) division division • Preganglionic neuron • Ganglionic neuron 5 Visceral effector A simple visceral reflex arc Response Figure 14.7 Figure 14.1 Dual Innervation Divisions at a Glance Parasympathetic Sympathetic Eye Eye Brain stem Salivary Skin* glands Cranial Salivary Sympathetic Sympathetic Parasympathetic glands • • ganglia Heart – “Fight or Flight” – “Rest and Digest” Cervical Lungs Lungs – NE and acetylcholine – Acetylcholine T 1 Heart – Thoracolumbar – Craniosacral Stomach Thoracic Stomach Pancreas Liver Pancreas and gall- L1 bladder Liver and Adrenal gall- Lumbar gland bladder Dual Innervation Bladder Bladder Genitals Genitals Sacral Figure 14.3 Parasympathetic Division Outflow Nerve Ganglia Effector Organ(s) Cranial (Terminal Ganglia) Outflow Oculomotor (III) Ciliary Eye Facial (VII) Pterygopalatine Salivary, nasal, and Submandibular lacrimal glands Glossopharyngeal Otic Parotid salivary glands (IX) Vagus (X) Within the walls of Heart, lungs, and most target organs visceral organs Within the walls of Large intestine, Sacral S2-S4 target organs urinary bladder, Outflow ureters, and reproductive organs 4 1/18/2016 Eye CN III Ciliary ganglion Lacrimal gland CN VII Pterygopalatine CN IX ganglionganglion Nasal CN X mucosa Submandibular ganglion Submandibular and sublingual Otic ganglion glands Parotid gland Central nervous system (CNS) Peripheral nervous system (PNS) Heart Cardiac and Parasympathetic pulmonary plexuses Lung Sensory (afferent) Motor (efferent) division Division division Liver and Celiac gallbladder Somatic nervous Autonomic nervous plexus = Craniosacral system system (ANS) Stomach Pancreas Sympathetic Parasympathetic S2 division Large division S4 intestine Pelvic Small splanchnic intestine nerves Inferior Rectum hypogastric plexus Urinary Genitalia Preganglionic bladder (penis, Postganglionic and ureters clitoris, and vagina) Cranial nerve Figure 14.4 Figure 14.1 Sympathetic Division = Thoracolumbar Eye Lacrimal gland Pons Nasal mucosa The Sympathetic Division Sympathetic trunk (chain) ganglia Blood vessels; Superior skin (arrector pili cervical muscles and ganglion sweat glands) Salivary glands Middle Preganglionic neurons originate in the spinal cervical • ganglion Heart Inferior cervical Cardiac and cord from T –L ganglion pulmonary Lung 1 2 T1 plexuses Greater splanchnic nerve – Thoracolumbar division Lesser splanchnic nerve Liver and Celiac ganglion gallbladder • FYI: Lateral horns L 2 Stomach White rami Superior communicantes mesenteric Spleen ganglion Adrenal medulla Kidney Sacral splanchnic nerves Lumbar Small splanchnic Inferior Preganglionic intestine nerves mesenteric (Sympathetic) ganglion Large intestine Cell Bodies Rectum Preganglionic Postganglionic Genitalia (uterus, vagina, and penis) and urinary bladder Figure 14.6 Spinal cord The Sympathetic Division Dorsal root 1) Ventral root 2) Spinal nerve 1) Preganglionic fibers leave through ventral root of spinal cord 3) Ventral ramus 4) White ramus communicans 2) Fibers join spinal nerve 5) Sympathetic trunk ganglion Sympathetic trunk 3) Spinal nerve divides at ventral rami Rib Gray ramus communicans 4) Rami branch immediately into white rami communicans Thoracic splanchnic nerves 5) Join sympathetic (paravertebral) ganglia (a) Location of the sympathetic trunk Figure 14.5a 5 1/18/2016 Sympathetic Division = Thoracolumbar Eye Lacrimal gland Sympathetic Trunk Ganglia Pons Nasal mucosa Sympathetic trunk (chain) ganglia Blood vessels; Superior skin (arrector pili cervical muscles and ganglion sweat glands) Salivary glands • Form longitudinal pathways adjacent to vertebral column Middle cervical ganglion Heart • Each spinal nerve has an associated ganglion (except in cervical Inferior cervical Cardiac and ganglion pulmonary Lung T1 region, where several ganglia fuse) plexuses Greater splanchnic nerve Lesser splanchnic nerve Liver and Celiac ganglion gallbladder L 2 Stomach White rami Superior communicantes mesenteric Spleen ganglion Adrenal medulla Kidney Sacral splanchnic nerves Lumbar Small splanchnic Inferior intestine nerves mesenteric ganglion Large intestine Rectum Preganglionic Postganglionic Genitalia (uterus, vagina, and penis) and urinary bladder Figure 14.6 The Sympathetic Division Lateral horn (visceral motor zone) Dorsal root Dorsal root ganglion • Sympathetic trunks and pathways Dorsal ramus of spinal nerve –Upon entering a sympathetic trunk ganglion a Ventral ramus of spinal nerve preganglionic fiber may do one of the following: Skin (arrector Gray ramus 1. Synapse with a ganglionic neuron within the same ganglion pili muscles communicans Ventral root and sweat White ramus Sympathetic glands) communicans trunk ganglion Sympathetic trunk To effector 1 Synapse at the same level Blood vessels (b) Three pathways of sympathetic innervation Figure 14.5b (1 of 3) Sympathetic Trunks and Pathways • Sympathetic trunks and pathways –Upon entering a sympathetic trunk ganglion a Skin (arrector preganglionic fiber may do one of the following: pili muscles and sweat 2. Ascend or descend the sympathetic trunk to glands) synapse in another trunk ganglion To effector Blood vessels 2 Synapse at a higher or lower level (b) Three pathways of sympathetic innervation Figure 14.5b (2 of 3) 6 1/18/2016 Sympathetic Trunks and Pathways • Sympathetic trunks and pathways –Upon entering a sympathetic trunk ganglion a preganglionic fiber may do one of the following: 3. Pass through the trunk ganglion and emerge Splanchnic nerve without synapsing Collateral ganglion (such as the celiac) Target organ in abdomen (e.g., intestine) 3 Synapse in a distant collateral ganglion anterior to the vertebral
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