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Peripheral Nervous System Anatomy

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Peripheral Nervous System Anatomy PERIPHERAL NERVOUS SYSTEM ANATOMY Chapters 13-16 of OpenStax Anatomy and Physiology with Additional Content from Gray’s Anatomy and Wikipedia Presented by John Nuttall OBJECTIVES Peripheral Nervous System •Describe the structure of the peripheral nervous system and functions of major structures: •Identify the layers of connective tissue in a nerve •List the cranial nerves in order: for each describe the major functions, central and peripheral connections, and pathway through cranium •List the major spinal nerves: for each describe which nerve plexus each supplies and the major functions •Contrast structure and function of autonomic and somatic efferent pathways of the PNS •Contrast the structure and function of sympathetic and parasympathetic division of the autonomic system FIGURE 13.21 Nerve Structure The structure of a nerve is organized by the layers of connective tissue on the outside, around each fascicle, and surrounding the individual nerve fibers (tissue source: simian). LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) FIGURE 13.23 The Cranial Nerves The anatomical arrangement of the roots of the cranial nerves observed from an inferior view of the brain. CRANIAL NERVES: 1 Source: Gray's Anatomy, Plate 771 Cribriform foramina CRANIAL NERVES: 2-5 Source: Gray's Anatomy, Plate 776 Optic foramen Superior Orbital (canal) Fissure CRANIAL NERVES: 2-6 Source: Gray's Anatomy, Plate 777 Superior Orbital Fissure Foramen rotundum CRANIAL NERVES: 5 Source: Gray's Anatomy, Plate 778 Superior Orbital Fissure Foramen rotundum Foramen ovale CRANIAL NERVES: 5 Source: Gray's Anatomy, Plate 784 CRANIAL NERVES: 7-8 Source: Gray's Anatomy, Plate 789 Internal Auditory (acoustic) Meatus CRANIAL NERVES: 9-11 Source: Gray's Anatomy, Plate 793 Jugular foramen CRANIAL NERVES: 10-12 Source: Gray's Anatomy, Plate 794 Hypoglossal canal SPINAL NERVES Source: wikipedia The formation of the spinal nerve trunk from dorsal and ventral roots. FIGURE 13.19 Dorsal Root Ganglion The cell bodies of sensory neurons, which are unipolar neurons by shape, are seen in this photomicrograph. Also, the fibrous region is composed of the axons of these neurons that are passing through the ganglion to be part of the dorsal nerve root (tissue source: canine). LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) FIGURE 13.20 Spinal Cord and Root Ganglion The slide includes both a cross-section of the lumbar spinal cord and a section of the dorsal root ganglion (see also Figure 13.19) (tissue source: canine). LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) SPINAL NERVES Source: Gray's Anatomy, Plate 675 Central canal Anterior white column Posterior white column Anterior gray horn Posterior gray horn (cell bodies of somatic motor neurons) Lateral gray horn Lateral (cell bodies of autonomic white column motor neurons) Dorsal root Ventral root (afferent fibers) (efferent fibers both somatic and autonomic) Dorsal root ganglion (cell bodies of sensory neurons) Dorsal ramus of spinal nerve Ventral ramus of spinal nerve (afferent and efferent fibers) (afferent and efferent fibers) FIGURE 13.22 Close-Up of Nerve Trunk Zoom in on this slide of a nerve trunk to examine the endoneurium, perineurium, and epineurium in greater detail (tissue source: simian). LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) FIGURE 13.24 Nerve Plexuses of the Body There are four main nerve plexuses in the human body. The cervical plexus supplies nerves to the posterior head and neck, as well as to the diaphragm. The brachial plexus supplies nerves to the arm. The lumbar plexus supplies nerves to the anterior leg. The sacral plexus supplies nerves to the posterior leg. CERVICAL PLEXUS C1-C5 Source: Gray's Anatomy, Plate 794 Cervical Plexus Phrenic Nerve C3-C5 CERVICAL PLEXUS C1-C5 Source: Gray's Anatomy, Plate 806 Phrenic Nerve Phrenic Nerve (Right) (Left) BRACHIAL PLEXUS C5-T1 Source: Gray's Anatomy, Plate 807 Branches Cords Divisions Trunks Roots Musculocutaneous (C5-7) Axillary (C5-6) Radial (C5-T1) Median (C6-T1) Ulnar (C8-T1) BRACHIAL PLEXUS C5-T1 Source: Gray's Anatomy, Plate 816 Median Musculocutaneous Ulnar Radial BRACHIAL PLEXUS C5-T1 Source: Gray's Anatomy, Plate 818 Axillary Radial LUMBAR PLEXUS T12-L4 Source: Gray's Anatomy, Plate 822 Femoral L2-L4 Obturator L2-L4 LUMBAR PLEXUS T12-L4 Source: Gray's Anatomy, Plate 827 Femoral L2-L4 Obturator L2-L4 SACRAL PLEXUS L4-S4 Source: Gray's Anatomy, Plate 828 Sciatic L4-S3 SACRAL PLEXUS L4-S4 Source: Gray's Anatomy, Plate 832 Sciatic Tibial Common fibular (peroneal) SACRAL PLEXUS L4-S4 Source: Gray's Anatomy, Plate 835 Common fibular (peroneal) Superficial fibular (peroneal) Deep fibular (peroneal) FIGURE 15.6 Comparison of Somatic and Visceral Reflexes The afferent inputs to somatic and visceral reflexes are essentially the same, whereas the efferent branches are different. Somatic reflexes, for instance, involve a direct connection from the ventral horn of the spinal cord to the skeletal muscle. Visceral reflexes involve a projection from the central neuron to a ganglion, followed by a second projection from the ganglion to the target effector. FIGURE 15.2 Connections of Sympathetic Division of the Autonomic Nervous System Neurons from the lateral horn of the spinal cord (preganglionic neurons) project to the chain ganglia on either side of the vertebral column or to collateral (prevertebral) ganglia that are anterior to the vertebral column in the abdominal cavity. Axons from these ganglionic neurons (postganglionic fibers) then project to target effectors throughout the body. FIGURE 15.3 Sympathetic Connections and Chain Ganglia The axon from a central sympathetic neuron in the spinal cord can project to the periphery in a number of different ways. (a) The fiber can project out to the ganglion at the same level and synapse on a ganglionic neuron. (b) A branch can project to more superior or inferior ganglion in the chain. (c) A branch can project through the white ramus communicans, but not terminate on a ganglionic neuron in the chain. Instead, it projects through one of the splanchnic nerves to a collateral ganglion or the adrenal medulla (not pictured). FIGURE 15.4 Connections of Parasympathetic Division of the Autonomic Nervous System Neurons from brainstem nuclei, or from the lateral horn of the sacral spinal cord, project to terminal ganglia near or within the various organs of the body. Axons from these ganglionic neurons then project the short distance to those target effectors. RESOURCES • Creative Commons Attribution-ShareAlike Copyright • Source for each slide is indicated in the top right corner. • Slide 1 was modified from slide 1 of the Chapter 13 OpenStax PowerPoint Image Slideshow • Narration and animations used in the recording of this presentation are modifications created by John Nuttall. • OpenStax: © Rice University under a CC-BY 4.0 International license; and may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. • Gray’s Anatomy: Henry Gray (1825–1861). Anatomy of the Human Body. 1918. http://www.bartleby.com/107/ • Wikipedia: Slide 13 from https://en.wikipedia.org/wiki/Spinal- nerve#/media/File:Spinal_nerve.svg was Vectorized in CorelDraw by Mysid on an existing image at en-wiki by Tristanb..
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