A&P Ch. 14 Nerves Part 1PPT PDF

Chapter 14 Spinal Cord and Spinal Nerves https://www.youtube.com/watch?v=KnD16 gwpCz8 https://www.youtube.com/watch?v=QY9NT Vh-Awo&t=15s https://www.youtube.com/watch?v=xXWsQ rl1N7s  Words To Know: Neuro = nerve Epi = above Sub = below Inter = between Myelo = s...

Chapter 14 Spinal Cord and Spinal Nerves https://www.youtube.com/watch?v=KnD16 gwpCz8 https://www.youtube.com/watch?v=QY9NT Vh-Awo&t=15s https://www.youtube.com/watch?v=xXWsQ rl1N7s  Words To Know: Neuro = nerve Epi = above Sub = below Inter = between Myelo = spinal cord -plegia = paralysis Encephalo = brain Duro = dura mater  Organization of the Nervous System Structural organization Functional organization Brain Sensory nervous system Motor nervous system Central detects stimuli and initiates and transmits nervous transmits information from information from the CNS system (CNS) Spinal cord receptors to the CNS to effectors Nerves Peripheral Somatic sensory Visceral sensory Somatic motor Autonomic motor nervous system (PNS) Ganglia Sensory input Sensory input that Motor output Motor output that is that is consciously is not consciously that is consciously not consciously or perceived from perceived from or voluntarily is involuntarily receptors (e.g., blood vessels and controlled; controlled; effectors eyes, skin, ears) internal organs effector are cardiac muscle, (e.g., heart) is skeletal muscle smooth muscle, and glands Afferent Efferent Ascending Descending Figure 12.1  Synapses Presynaptic neuron Postsynaptic neuron Chemical synapse – EPSP – IPSP  Nervous system terms Ganglion Cluster of neuron cell bodies in PNS Center Group of CNS neurons w/common function Nucleus Center with distinct anatomic boundaries Nerve Bundle of Axons in the PNS Nerve Plexus Nerve network Tract / CNS axon bundle w/similar function and common origin Fasiculi and destination Funiculus Groups of tracts in the spinal cord Pathway Centers with their associated tracts Decussation A tract that crosses between sides of the NS  Nervous System: Spinal Cord and Spinal Nerves The spinal cord – Provides a vital link between brain and rest of body – Exhibits some functional independence from the brain Spinal cord and spinal nerves – Pathway for sensory and motor nerve signals – Responsible for reflexes, quickest reactions to stimulus Spinal Cord and Spinal Nerves Spinal Nerves 31 pairs Spinal cord  Spinal Cord Gross Anatomy Spinal cord – Extends inferiorly from brain through vertebral canal – Ends at the level of L1 vertebra – Has rootlets coming off will form spinal nerves some forming interweaving nerves, nerve plexuses  Spinal Cord Gross Anatomy Spinal cord subdivisions – Cervical part superiormost part of spinal cord continuous with medulla oblongata contains neurons contributing to cervical spinal nerves – Thoracic part inferior to cervical part contains neurons for thoracic spinal nerves Cervical Region Thoracic Region  Spinal Cord Gross Anatomy Spinal cord subdivisions (continued) – Lumbar part short section inferior to thoracic part contains neurons for lumbar spinal nerves – Sacral part inferior to lumbar part contains neurons for sacral spinal nerves Lumbar Region Sacral Region  Spinal Cord Gross Anatomy Spinal cord subdivisions (continued) – Coccygeal part most inferior part of spinal cord contains neurons for single pair of coccygeal nerves – Vertebrae do not exactly match up with spinal cord division due to longer vertebrae growth than spinal cord growth in adult, spinal cord shorter than vertebral canal Coccygeal Region  Spinal Cord Gross Anatomy Spinal cord subdivisions (continued) – Conus medullaris tapering end marking end of spinal cord proper – Cauda equina nerve roots projecting inferiorly from spinal cord – thin strand of pia mater – helps anchor conus medullaris to coccyx Medullary Cone & Cauda Equina  Spinal Cord Conus medullaris Filum terminale Cauda equina 19  Copyright © The McGraw-Hill Companies, Inc. 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Atlas C1 Cervical plexus C2 C3 Cervical part C4 C5 Gross Cervical enlargement C6 C7 C8 T1 vertebra Anatomy of Brachial plexus T1 T2 T3 the Spinal T4 T5 Cord: Thoracic part T6 T7 Posterior T8 T9 View T10 T11 (Figure Lumbosacral enlargement T12 Lumbar part L1vertebra 14.1a) Conus medullaris Sacral part L1 L2 Lumbar plexus L3 Cauda equina L4 L5 Sacral plexus S1 S2 S3 S4 Filum terminale S5 Co1 (a) Posterior view  Spinal Cord Gross Anatomy Spinal nerves (see next two slides for help) – 31 pairs contain both sensory and motor axons identified by first letter of spinal cord part and number 8 cervical nerves (C1-C8) 12 thoracic nerves (T1-T12) 5 lumbar nerves (L1-L5) 5 sacral nerves (S1-S5) 1 coccygeal nerve (Co1)  Odd Numbering System C1 – C7 emerge above the vertebrae named for.  Odd Numbering System All others emerge below the vertebrae name for: – C8 – T1-T12 – L1 – L 5 – S1 – S5 – C0 or Co1  Spinal Cord Gross Anatomy Spinal cord features – Cervical enlargement larger diameter of spinal cord in cervical region due to neurons that innervate the upper limbs – Lumbosacral enlargement larger diameter of spinal cord in mid-lumbar region due to neurons that innervate the lower limbs See Table 14.1: Cross Sections of Representative Parts of the Spinal Cord Cervical & Lumbosacral Enlargements  Protection and Support of the Spinal Cord SPINAL MENINGES – Encapsulate the spinal cord REMEMBER: continuous with cranial meninges – Structures and spaces encircling the spinal cord (from outside  in Vertebra epidural space dura mater subdural space arachnoid mater subarachnoid space pia mater  Meninges of Spinal Cord https://basicmedicalkey.com/the-nervous-system-2/  Protection and Support of the Spinal Cord SPINAL MENINGES – Epidural space lies between dura mater and inner walls of the vertebra has areolar connective tissue, blood vessels, adipose tissue epidural anesthetics introduced here – Dura mater deep to epidural space provides stability to spinal cord fuses with connective tissues surrounding nerves  Protection and Support of the Spinal Cord SPINAL MENINGES – Pia mater deep to subarachnoid space innermost meningeal layer of elastic and collagen fibers adheres to spinal cord and supports blood vessels – Denticulate ligaments triangular extensions of spinal pia mater attach to dura mater help suspend and anchor spinal cord laterally  Spinal Meninges and Structure of the Spinal Cord: Cross Section (Figure 14.2a) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior Spinous process of vertebra Epidural space Denticulate ligament Dura mater Spinal nerve Subdural space Arachnoid mater Subarachnoid space Intervertebral foramen Pia mater Spinal cord Body of vertebra Anterior (a) Cross section of vertebra and spinal cord  Spinal Meninges and Structure of the Spinal Cord: Anterior View (Figure 14.2b) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. White matter Gray matter Posterior median sulcus Central canal Posterior rootlets Anterior median fissure Pia mater Posterior root Posterior root ganglion Spinal nerve Anterior root Subarachnoid space Arachnoid mater Anterior rootlets Subdural space Dura mater (b) Anterior view  Spinal Nerves Dorsal/Posterior Roots – Sensory (IN) fibers – Afferent Ventral/Anterior Roots – Motor (OUT) fibers – Efferent (Exit) *IN the back; OUT the front Anatomy Dorsal and Ventral roots re-combine to form the Spinal Nerve. Spinal Nerve is short ~ 1 Inch Immediately branches into Rami Dorsal rootlets Spinal Nerve Ventral rootlets Dorsal root Ventral root Dorsal root Spinal nerve gangion  Sectional Anatomy of Spinal Cord Gray matter – Made of neuron’s cell bodies, dendrites, and unmyelinated axons; also glial cells – Looks like “H” or a butterfly Masses of grey matter project from center of spinal cord – Anterior horns house cell bodies of somatic motor neurons – Lateral horns house cell bodies of autonomic motor neurons o Only present in parts T1–L2 – Posterior horns house axons of sensory neurons and cell bodies of interneurons 35  Gray Matter and White Matter Organization in the Spinal Cord Figure 14.4 36  Sectional Anatomy of Spinal Cord Gray commissure – Horizontal band of gray matter surrounding central canal – Contains unmyelinated axons connecting left and right gray matter Nuclei: groups of cell bodies – Sensory nuclei in posterior horn contain interneurons o Somatic sensory nuclei receive signals from skin, muscle, joints o Visceral sensory nuclei receive signals from blood vessels, viscera – Motor nuclei in anterior and lateral horns contain motor neurons o Somatic motor nuclei (anterior) innervate skeletal muscle o Autonomic motor nuclei (lateral) innervate smooth muscle, heart, glands 37  Neuron Pathways and Nuclei Locations Figure 14.5 38  Spinal Cord Gray matter White matter 39  Sectional Anatomy of Spinal Cord White matter: myelinated axons to and from the brain Regions of white matter – Posterior funiculus o Sits between posterior gray horns and posterior median sulcus o Contains sensory tracts (axon bundles called fasciculi) – Lateral funiculus o Sits on lateral sides of spinal cord o Contains ascending (sensory) and descending (motor) tracts – Anterior funiculus o Sits between anterior gray horns and anterior median fissure o Left and right anterior funiculi are interconnected by white commissure o Contains ascending (sensory) and descending (motor) tracts 40  Gray Matter and White Matter Organization in the Spinal Cord (Figure 14.3) Copyright © The McGraw-Hill Companies, Inc. 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Posterior White matter Central canal Posterior median sulcus Gray matter Posterior horn Posterior funiculus Gray commissure Lateral funiculus Lateral horn White commissure Anterior horn Anterior funiculus Posterior White matter Central canal Gray matter Posterior horn Gray commissure Lateral horn Anterior horn LM 10x Anterior median fissure Anterior Anterior (a) Gray and white matter (b) Transverse section (b): © Dr. David Phillips/Visuals Unlimited Spinal Cord Conduction Pathways: Overview Conduction pathways characteristics – Sensory pathways AKA ascending pathways signals from sensory receptors going to brain – Motor pathways AKA descending pathways signals from brain to muscles or glands Spinal Cord Conduction Pathways: Overview Conduction pathways characteristics – Paired tracts: One side matches the other – Composed of 2 or more neurons: Most pathways are a series of 2 to 3 neurons. – Common location of neuron cell bodies: Cell bodies are found in 1 of 3 places. 1) posterior root ganglion 2) gray horns 3) nuclei within brain – Common location of axons: Axons of different neurons are found in spinal nerves, spinal cord, and brain. – Decussitation (cross over from one side of body to other) contralateral, relationship to opposite side ipsilateral, relationship to same side  Spinal Cord Conduction Pathways: Sensory Pathways Sensory pathways – Ascending pathways – Carry info about proprioception, touch, temperature, pressure, pain Two Types: – Somatosensory pathways process stimuli from skin, muscles, joints – Viscerosensory pathways process stimuli from viscera (internal organs)  Spinal Cord Conduction Pathways: Sensory Pathways Neuron series in sensory pathway – Primary neuron first neuron in chain axon projecting to secondary neuron within CNS – Secondary neuron Interneuron (between) projects to thalamus or cerebellum secondary neuron to thalamus projecting to tertiary neuron – Tertiary neuron interneuron residing in thalamus axon projects to primary somatosensory cortex  Spinal Cord Conduction Pathways: Motor Pathways Motor pathways – Descending pathways in the brain and spinal cord – At least two motor neurons present in pathway: upper motor neuron – housed within cerebral cortex or nuclei within brainstem lower motor neuron – housed within anterior horn of spinal cord or brainstem cranial nucleus – exit CNS and project to skeletal muscle – always excitatory Sensory & Motor Pathways  Spinal Cord Conduction Pathways: Motor Pathways Two motor pathway components – Direct/Pyramidal pathways use chain of 1 or 2 motor neurons to communicate Two types: – Lateral corticospinal tracts: 85%of direct pathways » Innervates skeletal muscles that control skilled movements in the limbs – Anterior corticospinal tract: 15 % of direct pathways » Innervates axial skeletal muscles  Pathway direction Right side of body Left side of body Cerebrum Primary motor cortex (precentral gyrus) Internal capsule Thalamus Upper motor Corticospinal neurons Tracts (Figure Midbrain Corticospinal tracts (anterior and lateral tracts) 14.10) Cerebral peduncle Fourth ventricle Medulla oblongata Anterior corticospinal tract Decussation in pyramids To skeletal of medulla oblongata muscles Lateral corticospinal tract Lower motor neurons Spinal cord Decussation in spinal cord  Spinal Cord Conduction Pathways: Motor Pathways Indirect Pathway – Named because of its “indirect” path – responsible for subconscious or unconscious control – Two types: Lateral: regulates and controls precise, discrete movements and tone in flexor muscles of the limbs Medial: regulates reflexive muscle tone and gross movements of the head, neck, and proximal parts of limbs and trunk – Initiates motor commands subconsciously or reflexively – Modifies or helps control somatic motor activity  Spinal Nerves Spinal nerve characteristics – Formed from motor and sensory axons – Enveloped in successive connective tissue wrappings – Anterior root (ventral root) formed from multiple anterior rootlets arising from spinal cord contains motor axons only cell bodies found in anterior and lateral horns of spinal cord  Spinal Nerves Posterior root (dorsal root) formed from posterior rootlets entering spinal cord contains sensory axons only cell bodies located in posterior root ganglion – within posterior root – Anterior root and posterior root unite within intervertebral foramen become spinal nerve  Spinal Nerves Spinal nerve characteristics (continued) – Cervical nerves travel through intervertebral foramen superior to vertebra of same number – e.g., second spinal nerve – exits through foramen between C1 and C2 vertebrae exception: 8th cervical nerve – travels through foramen interior to vertebra of same number – i.e.., leaves foramen between C7 and T1  Spinal Nerves Spinal nerve characteristics (continued) – Nerves inferior to C8 travel through intervertebral foramen inferior to vertebra of same number e.g., second thoracic nerve exits through foramen between T2 and T3  Spinal Nerves Spinal nerve characteristics (continued) – Roots of lumbar and sacral nerves travel inferiorly to reach respective intervertebral foramina much longer than roots of other spinal nerves because spinal cord shorter than vertebral canal  Spinal Nerves Distribution of spinal nerves – After intervertebral foramen, nerve split into branches – Posterior ramus (branch) smaller innervates deep muscles of back, skin of back – Anterior ramus larger splits into multiple other branches innervate anterior and lateral trunk, upper limbs, lower limbs  Posterior Spinal root nerves ganglia Posterior Anterior rami rami  Posterior ramus Anterior ramus Rami Sympathetic Gray ramus White ramus ganglion  Spinal Nerves Distribution of spinal nerves – Rami communicantes additional rami associated with autonomic nervous system (ANS) extend between spinal nerve and sympathetic trunk ganglion – ganglia interconnected in sympathetic trunk – parallel and lateral to vertebral column  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior Spinous process Deep muscles of back Posterior root Posterior root ganglion Posterior ramus Spinal cord Anterior ramus Spinal nerve Anterior root Rami communicantes Spinal Nerves Sympathetic trunk ganglion (Figure 14.12) Body of vertebra Anterior  Spinal Nerves: Overview Dermatomes – Specific segment of skin supplied by single spinal nerve – All spinal nerves except C1 – Skin divided into segments into a dermatome map – E.g., horizontal skin around umbilicus supplied by anterior ramus of T10  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. C2 Trigeminal nerve (CN V) C2 C3 C4 C5 C3 C6 C7 C4 C8 C5 T1 T1 T2 T2 C5 C5 T3 T3 T4 T4 T2 T2 T5 T5 T6 T6 T1 T1 Dermatome T7 T8 T7 T8 T9 Maps T9 T10 C7 T11 C7 T10 T12 C6 C6 C8 C8 (Figure C5 T11 T12 C5 L1 L2 L3 14.13) L1 L1 L4 S2 S3 S4 S3 S5 C6 C6 Co L2 L2 L5 L5 C7 C8 C8 C7 L1 S1 S1 L3 L3 S2 S2 L2 L2 L4 L4 L3 L5 L5 S1 S1 L4 S1 S1 L5 L5 Anterior view Posterior view  Hilton’s Law Any nerve serving a muscle that produces movement at a joint, Also Innervates the joint and the skin over that joint.  Spinal Nerves: Overview Dermatomes (continued) – Can indicate potential damage to one or more spinal nerves e.g., loss of sensation on medial arm and forearm C8 may be damaged – Involved in referred visceral pain pain from one organ referred to a dermatome e.g., appendix innervated by axons from T10 appendicitis with referred visceral pain to T10 region  Spinal Nerves: Nerve Plexuses Nerve plexus – Network of interweaving anterior rami of spinal nerves – Anterior rami of most spinal nerves form plexuses on both right and left sides – Main plexuses cervical plexuses brachial plexuses lumbar plexuses sacral plexuses  Spinal Nerves: Nerve Plexuses Nerve plexus organization – Damage to single spinal nerve innervation to muscle or skin region not totally lost  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spinal nerve Posterior ramus Posterior root Anterior root Anterior ramus Posterior root ganglion Rami communicantes Sympathetic trunk ganglion Sympathetic trunk Intercostal Nerves (Figure 14.14)  Cervical Plexus (Figure 14.15) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anterior rami Cervical plexus branches Other nerves (not part of cervical plexus) C1 Atlas Hypoglossal nerve (XII) Accessory nerve (XI) C2 Segmental branches Axis C3 Lesser occipital nerve Great auricular nerve Transverse cervical nerve C4 Superior root Ansa cervicalis Inferior root C5 Branch to brachial plexus Supraclavicular nerves Phrenic nerve Seven Shakras and Acupuncture  Spinal Cord Gross Anatomy Clinical View: Lumbar Puncture – Procedure for obtaining CSF for medical diagnosis – Needle passed through: Skin Back muscles Epidural space Dura mater Arachnoid mater Into the Subarachnoid space to extract CSF  Spinal Cord Clinical View: Spinal Cord Injuries – May leave individuals paralyzed and unable to perceive sensations Prompt use of steroids after injury – may reduce function loss Early antibiotics – have reduced number of deaths due to pulmonary and urinary infections Neural stem cells – may be used in future to regenerate CNS axons  Spinal Nerves: Overview Clinical View: Shingles – Reactivation of chickenpox infection – Virus remaining latent in posterior root ganglia – Reactivated, travels through sensory axons to dermatome – Rash and blisters along the dermatome – Burning and tingling pain – Antiviral medication to reduce severity – Vaccine to prevent or reduce disease severity end