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Spinal Cord Spinal Nerves Chapter 10 Spinal Cord Part of the CNS About 16-18 inches long Extends from the foramen magnum to the end of L1 Main pathway for information flow to and from the brain Gross Anatomy of the Spinal Cord Cord is divided into 31 segments: cervical, thoracic, lumbar and sacral Cervical and lumbar diameter enlargements Covered by same membranes as the brain At about L1 the cord divides into many long ventral and dorsal roots called the cauda equina (horses tail) Internal structure 2 grooves divide spinal cord in ½ : (anterior median fissure and posterior median sulcus) Spinal Cord White Matter White matter is divided into columns Columns contain TRACTS; composed of axons of similar structure/function All axons in a tract relay information in the same direction Specific tracts convey either sensory or motor commands: ASCENDING TRACTS relay sensory information toward the brain DESCENDING TRACTS relay motor information into the spinal cord Spinal Cord Gray Matter Gray matter is organized into nuclei – neuron cell bodies, dendrites, unmyelinated axons, neuroglia “Horns” (anterior, posterior, lateral): Anterior: Motor nuclei send out commands to peripheral effectors, skeletal muscles Posterior: Sensory nuclei receive and relay sensory information Lateral: autonomic motor neurons (smooth muscle, cardiac muscle, glands) Nerve Distribution - sensory Nerve Distribution - motor Spinal Cord and Meninges Spinal cord and meninges (layers of connective tissue) Outer= Dura mater (“tough mother”) Middle= Arachnoid mater (“spider mother”) Inner= Pia mater (“delicate mother”) Ganglia and roots Each spinal segment has a pair of dorsal root ganglia (sensory neuron cell bodies). Dorsal root enters cord; ventral root leaves cord Dorsal root ganglia – sensory neuron cell bodies (bulge) Ventral root – motor output Dorsal root – sensory input Spinal nerve - mixed Spinal nerves extend out through the intervertebral foramen. After passing through the intervertebral foramen a spinal nerve divides into several branches = plexus (cervical, brachial, lumbar, sacral) Cervical Plexus Brachial plexus Brachial plexus Lumbar plexus and Sacral plexus Epidural Epidural analgesia Pain medication placed into the epidural space Often used to block pain associated with child birth Continuous infusion Blocks pain not muscle activity Some of the reasons your doctor may want to do a spinal tap include the following: ◦ To look for infection (bacteria) ◦ To check to see if there is bleeding around the brain (small amounts of blood will be found in the fluid) ◦ To look for causes of unexplained seizures ◦ To look for causes of headaches ◦ To evaluate for uncommon diagnoses such as multiple sclerosis, Lyme disease, GuillainBarré syndrome, and several others. ◦ To administer certain types of chemotherapeutics medications in the treatment of some cancers Spinal Tap: removal of CSF Spinal Cord Injuries Two general types of injuries Complete - no function below the affected area of the cord – C1 - C3 injury breathing affected - respirator – C4 - C7 quadriplegia (arms and legs) Incomplete - some function below the affected area of the cord – Thoracic area and below - paraplegia (legs) Types of paralysis Cause of Spinal Cord Injuries Sudden traumatic blow to spine that fractures or dislocates vertebrae Bone fragments, disc material bruise or tear the spinal cord tissue Cord swells, blood supply cells can stop, neurons die, cord is damaged beyond repair Treatment of Spinal Cord Injuries Minimize further injury – Realign spine and immobilize (surgery) – Steroid medication to reduce swelling – Methylprednisolone in first 8 hours reduces swelling, inflammation and nerve cell damage Rehabilitation Dealing with long term complications