You Should Be Able To Exam 4 1 Describe the gross anatomy of the spinal cord a About 18 inches 45 cm long b inch 14 mm wide c Ends between vertebrae L1 and L2 d Bilateral symmetry i Grooves divide the spinal cord into left and right 1 Posterior median sulcus 2 Anterior median fissure on posterior side deeper groove on anterior side e Enlargements of the spinal cord i Caused by 1 Amount of gray matter in segment 2 Involvement with sensory and motor nerves of limbs ii Cervical enlargement iii Lumbar enlargement 1 Nerves of shoulders and upper limbs 1 Nerves of pelvis and lower limbs f The Distal End i Conus medullaris ii Filum terminale iii Cauda equine 1 Thin conical spinal cord below lumbar enlargement 1 Thin thread of fibrous tissue at end of conus medullaris 2 Attached to coccygeal ligament into sacrum g Is it symmetrical along the entire length i Yes unless there is a problem h Spinal cord segments i Based on vertebrae where spinal nerves originate ii Positions of spinal segment and vertebrae change with age 1 Cervical nerves a Inferior vertebra 2 All other nerves a Superior vertebra 1 Nerve roots ventral and dorsal extending below conus medullaris and 2 Explain how spinal nerves are numbered a Spinal nerve generally refers to a mixed spinal nerve which carries motor sensory and autonomic signals between the spinal cord and body b Humans have 31 left right pairs of spinal nerves c They roughly correspond to a segment of the vertebral column i 8 cervical 1 C1 C8 ii 12 thoracic 1 T1 T12 d Spinal nerves are part of PNS 3 Describe the difference between the ventral and dorsal root a Each spinal nerve is formed by the combination of nerve fibers from the dorsal and 4 Describe the meninges covering the spinal cord a Specialized membranes isolate the spinal cord from surroundings b Continuous with cranial meninges c Functions of the spinal meninges include i Viral or bacterial infection of meninges ii Spinal meningitis or cerebral meningitis can disrupt CSF flow damage or kill iii 5 lumbar iv 5 Sacral 1 L1 L5 1 S1 S5 v 1 coccygeal ventral roots of the spinal cord b Dorsal Root i Carry afferent sensory axons ii TO CNS c Ventral root i Carry efferent motor axons ii AWAY CNS i Protect spinal cord ii Carry blood supply d Meningitis neurons and neuroglia e 3 Meningeal Layers i Dura mater 1 Outer 2 Tough and fibrous 3 Cranially a Fuses with periosteum of occipital bone b Is continuous with cranial dura mater 4 Caudally 5 Epidural space a Tapers to dense cord of collagen fibers b joins filum terminale in coccygeal ligament a Between spinal dura mater and walls of vertebral canal b Contains loose connective and adipose tissue c Anesthetic injection site ii Arachnoid mater 1 Middle 2 Arachnoid membrane a Simple squamous epithelia b Covers outer surface of arachnoid mater 3 Subdural space 4 Subarachnoid space a Between arachnoid mater and dura mater a Between arachnoid mater and pia mater b Contains collagen elastin fiber network i Extends into filum terminale c Filled with cerebrospinal fluid i Carries dissolves gases nutrients wastes ii Lumbar puncture or spinal tap withdraws CSF iii Spinal anesthesia 1 Injection of local anesthetics to subarachnoid space spreads as CSF distributes along spinal cord iii Pia mater Inner 1 2 Mesh of collagen and elastic fibers 3 Bound to underlying neural tissue 4 Blood vessels serving the spinal cord run along surface of pia mater within subarachnoid space 5 Describe the difference between the gray and white matter found in the spinal cord a White matter i Superficial ii Contains myelinated and unmyelinated axons iii Organization 1 Organized in columns 2 Tracts or fasciculi a Bundles of axons in white columns b Relay same information in same direction c Ascending tracts i Carry information to brain d Descending tracts i Carry motor commands to spinal cord b Gray matter i Surrounds central canal of spinal cord ii Covered by a thick layer of white matter iii Contains neuron cell bodies neuroglia and unmyelinated axons iv Has projections gray horns v Organization 1 Cell bodies of neurons form functional groups called nuclei remember ganglia are clusters of cell bodies in the PNS a Sensory nuclei i Dorsal posterior ii Connect to peripheral receptors b Motor nuclei i Ventral anterior ii Connect to peripheral effectors vi Sensory or motor nucleus location within the gray matter determines which body part it controls 6 Explain the function of the gray horns of the spinal cord a Posterior gray horns i Contain somatic and visceral sensory nuclei b Anterior gray horns c Lateral gray horns i Contain somatic motor nuclei In thoracic and lumbar segments i ii Contain visceral motor nuclei d Gray commissures i Axons that cross from one side of cord to the other BEFORE reaching gray matter 7 Explain the function of the white columns of the spinal cord a Posterior White columns i Lie between posterior gray horns and posterior median sulcus ii Proprioception fine touch ventral pressure vibrations b Anterior White columns i Lie between anterior gray horns and anterior median fissure ii Anterior white commissure 1 Area where axons cross from one side of spinal cord to the other c Lateral White columns i Located on each side of spinal cord between anterior and posterior columns 8 Describe the connective tissue layers covering the spinal nerves a 3 connective tissue layers of spinal nerves i Epineurium ii Perineurium 1 Outer layer 2 Dense network of collagen fibers 1 Middle layer 2 Divides nerve into fascicles axon bundles iii Endoneurium Inner layer 1 2 Surrounds individual axons 9 Describe the locations and function of the major nerve plexuses a Nerve Plexuses i Complex interwoven networks of nerve fibers ii Formed from blended fibers of ventral rami of adjacent spinal nerves iii Control skeletal muscles of the neck and limbs b 4 Major Nerve Plexuses of Ventral Rami i Cervical Plexus 1 Includes ventral rami of spinal nerves C1 C5 Innervates neck thoracic cavity diaphragmatic muscles 2 3 Major nerve a Phrenic nerve b Damage to this nerve can cause you to stop breathing C3 5 controls diaphragm ii Brachial Plexus Includes ventral rami of spinal nerves C5 T1 Innervates pectoral girdle and upper limbs 1 2 3 Major Nerves flex arm receives sensory info on extensor muscles of arm and forearm receives b Radial nerve a Musculocutaneous nerve lateral surface of forearm sensory info from poserolateral surface anterolateral hand surface of hand c Median nerve e Axillary nerve d Ulnar nerve
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