Georgia Latham, MD January 2016

Anatomically, nervous system divided into :  Central Nervous System (CNS) ▪ main processor of information ▪ includes the brain and spinal cord  Peripheral Nervous System (PNS) ▪ parts of nervous system outside the brain and spinal cord ▪ connects the CNS to the body's organs and extremities ▪ relays commands issued by the CNS ▪ relays information from the body and outside world back to the CNS

 Somatic Nervous System ▪ involved in the control of mostly voluntary activities  Autonomic Nervous System (ANS) ▪ connects CNS to internal organs and glands of the body ▪ involved in regulating involuntary functions such as heartbeat  Subdivisions of ANS: ▪ Sympathetic nervous system  mobilizes energy and resources during times of stress and arousal ▪ Parasympathetic system  conserves energy and resources during relaxed states

Divisions of Human Nervous System

Brain and Spinal Cord  Encased in a series of membranes called MENINGES: ▪ Pia Mater  attached directly to the spinal cord  contains the cord's blood supply ▪ Arachnoid  middle layer  holds CSF in place ▪ Dura mater  tough fibrous outer layer  Cerebrospinal fluid (CSF) ▪ acts to cushion the spinal cord ▪ flows between pia mater and arachnoid

 contains bundles of nerve fibers that extends from the brain down the back  communication cable between the brain and rest of the body, relaying information back and forth  critical part of the nervous system  about 18 inches long and the width of the pinky finger  fairly fragile

29 vertebrae or back bones ▪stack on top of each other to form the spinal column ▪spongy cartilage (disc) between vertebrae, acts as shock absorber View from top Lateral view Vertebra Each vertebra has a hole (foreman ) With vertebrae stacked on top of each other, these foreman form the spinal canal, a bony tunnel that protects the spinal cord

Four major segments: 1.Cervical vertebrae (7)  make up the neck 2.Thoracic vertebrae (12)  extend to about the waist  serve as attachments for ribs 3.Lumbar vertebrae (5)  five vertebrae of lower back 4.Sacrum  flat v-shaped bone  made of 5 fused vertebrae  anchors the spine to the pelvis  Coccyx (tailbone)  attached to bottom of sacrum  also made up of fused vertebrae

Autonomic Nervous System Cervical Upper Thoracic

Autonomic Nervous System Thoracic Lumbar

Sympathetic Nervous System

Autonomic Nervous System

project off left and right sides of the spinal cord to every part of the body

SPINAL NERVES

The spinal cord is shorter than the bony spine, ending just below the 12 th rib, far above the tailbone Long extensions of lumbar, sacral and coccygeal spinal nerves descend through the spinal canal, forming the cauda equina (Latin for “horse’s tail”), exiting the spinal column at the corresponding level of the vertebra or in the sacrum.

SPINAL NERVES 31 pairs  8 cervical (C1 - C8)  12 thoracic (T1 – T12)  5 lumbar (L1 – L 5)  5 sacral (S1-S5)  1 coccygeal (Cx) Cx

Each spinal nerve is formed by a dorsal root carrying sensory information to the CNS and a ventral root carrying motor information from the CNS to muscles and organs.

 deliver information about body position from muscles and joints to the spinal cord  transmit sensations from skin ▪ touch ▪ pressure ▪ pain ▪ temperature  information enters spinal cord through the dorsal root and is transmitted up to the brain

 pass information from the brain to muscles, directing precise voluntary movements Cervical spinal nerves  supply the muscles of the neck, shoulders, arms and hands, and diaphragm ▪ `` Thoracic spinal nerves  supply truck muscles, including intercostal muscles that are involved in breathing Lumbar spinal nerves  supply hip, leg and foot muscles Sacral spinal nerves  supply anal and urethral sphincters

relate to the muscles or group of muscles (and their respective movements) that come from particular levels of the spinal cord CERVICAL MYOTOMES C3 Diaphragm (breathing) C4 Diaphragm (breathing, shoulder shrug) C5 Deltoid (lifts arms) Biceps (bends elbow) C6 Wrist extensors (lifts wrist back) C7 Triceps (straightens elbow) C8 Hands and fingers THORACIC MYOTOMES T1 Hands & fingers T2 Chest muscles T3 Chest muscles T4 Chest muscles T5 Chest muscles T6 Chest & abdominal muscles T7 Chest & abdominal muscles T8 Abdominal muscles T9 Abdominal muscles T10 Abdominal muscles T11 Abdominal muscles T12 Abdominal muscles

 T1-12 power the muscles that lie between the ribs (intercostal muscles). These also help you breathe by drawing the rib cage outwards and upwards, pulling the lungs in the same direction. The lungs expand, helping them fill with air.  The diaphragm and the intercostal muscles are your major breathing muscles.  Your lower thoracic spinal nerves T6-12 provide power to your abdominal muscles. These muscles help you cough and expel matter from your air passages. Abdominal muscles are also important in balance and posture.  injury/what-happens-to-the-spinal-cord-after- injury/spinal-nerves-up-close

Each "nerve" in the body is a collection of many individual sensory and motor nerve cells or neurons.  NEURONS  many different types with different shapes and structures  Three main regions: 1. cell body  metabolic or manufacturing center of the neuron  makes nutrients and structures necessary for the neuron to live and function 2. dendrites  fine tubular extensions that radiate from the cell body like antennae  major receptors of information from other cells 3. axon (also called the nerve fiber)  long stem that extends away from the cell body  conducts signals from the nerve cell to distant targets  SYNAPSE  Junction (gap) between neurons where signals are transmitted from one nerve cell to another

 special insulation surrounds axons of most large neurons  maximizes conduction of the nerve signal down long axons  increases speed and efficiency with which a signal is transmitted  required for proper function MYELIN is formed by glia cells: oligodendrocytes in CNS Schwann cells in PNS NEURON axon

GLIA (Greek for “glue”) are nerve support cells Include ASTROCYTES in CNS, as well as cells that make up myelin: SCHWANN CELLS in PNS OLIGODENDROCYTES in CNS  provide mechanical support and other vital functions for nerve cells Damage or disease to the glia can result in loss of nerve function.

maintain chemical balance supply nutrients for nerve cells clear out debris after neuronal death or injury Outnumber nerve cells by at least 10:1

Spinal Cord Cross-section

UPPER MOTOR NEURONS (UMN) nerves within the CNS that are involved in controlling movement; cell body is located in the brain and the long axon runs through spinal cord LOWER MOTOR NEURONS (LMN) nerves that leave the spinal cord to connect to muscles UMN cross to opposite side at level of medulla

can result from damage to the vertebral column or to the spinal cord itself most commonly occurs when trauma or injury to the vertebral column causes a fracture of bones or tearing of ligaments Bone displacement can result in: spinal-cord bruising (contusion) pinching (compression) stretching (distraction) any combination of above

 rare  most commonly result of gunshot or stab wound  can occur with or without damage to surrounding vertebra Severed Cervical Spine Dislocation of C5 over C6

Ischemia (inadequate blood supply)  can result in death of neurons and glia Potential causes : ▪ injury ▪ disease ▪ surgical procedures  especially with aorta clamping  very rare

0 30 min Time hours hours hours of Injury Initial “primary”” injury  mechanical damage to neurons, glia, and blood vessels Initial “primary”” injury  mechanical damage to neurons, glia, and blood vessels Hemorrhage (bleeding) into central gray matter Hemorrhage (bleeding) into central gray matter Ischemia Inflammatory cells invade Inflammatory cells invade inflammatory cells begin killing damaged cells inflammatory cells begin killing damaged cells edema develops HYPOXIA Apoptosis & Necrosis Apoptosis & Necrosis Secondary Injury

0 30 min Time hours hours hours of Injury Initial “primary”” injury  mechanical damage to neurons, glia, and blood vessels Initial “primary”” injury  mechanical damage to neurons, glia, and blood vessels Ischemia Inflammatory cells invade Inflammatory cells invade edema develops HYPOXIA Apoptosis & Necrosis Apoptosis & Necrosis Secondary Injury TIME LINE Apoptosis (cell death) & Necrosis (tissue death) Apoptosis (cell death) & Necrosis (tissue death) inflammatory cells begin killing damaged cells inflammatory cells begin killing damaged cells Secondary Injury Hemorrhage (bleeding) into central gray matter Hemorrhage (bleeding) into central gray matter

 Upper Motor Neuron (UMN) injury ▪messages from the brain are cut off at the level of SCI  LMNs react without limit or inhibition  uncontrolled muscle contractions  muscle spasms can either be  "alternating" (producing twitching or shaking)  "sustained" (causing rigidity in the limbs)  spasticity (“spastic paralysis”)  Lower Motor Neuron (LMN) damage  muscles of the limbs get cut off from nerves that supply them  muscles become limp or flaccid (“flaccid" paralysis)

 Loss of control  breathing  bladder  bowel  sexual function  subconsciously controlled functions (e.g. blood pressure and sweating)  Loss of sensation  pain  discomfort  Autonomic Dysreflexia (AD)  serious condition that may occur in individuals with SCI at or above T6  potentially life threatening (can lead to stroke)

 LEVEL OF INJURY  defined as "the most caudal” (lowest) segment of the spinal cord with normal sensory and motor function on both sides of the body  the higher the injury of the spinal cord, the more dysfunction can result  TYPE ▪ Complete  no voluntary movement or sensation exists below the injury level ▪ Incomplete  some feeling or voluntary movement remains below injury level

CERVICAL SPINAL CORD INJURIES

Most severe of spinal cord injuries. Can result in:  inability to breathe (requiring mechanical ventilation)  inability to cough  inability to speak or speech impairment  paralysis in neck, arms, hands, trunk, and legs (quadriplegia)  loss of control of bladder and bowels  complete assistance required for activities of daily living (ADL) (e.g. eating, dressing, bathing, and getting in or out of bed)

 able to breathe without mechanical ventilation, but breathing weakened  speech not usually impaired  little or no voluntary control of bowel or bladder  paralysis of trunk and legs typical  the higher the level of injury, the more functional loss  corresponding nerves control arms and hands; muscle control of upper extremities are specific to level

SHOULDER ABDUCTION raise arms at shoulder ELBOW FLEXION bend elbows

WRIST EXTENSION bend wrists back

WRIST FLEXION SOME FINGER EXTENSION SHOULDER ADDUCTION  normal shoulder movements ELBOW EXTENSION  normal elbow movements

FINGER FLEXORS grasp and release

FINGER FLEXORS grasp and release

Spinal Nerve Movements C5Shoulder abduction Elbow flexion C6Wrist extension C7Elbow extension Some finger extension C8Hand movements : Grasp

CERVICAL SENSORY INNERVATION

GradeTypeDescription A Complete No motor or sensory function in sacral segments S4-5 B Incomplete Sensory but no motor function below the neurological level. Extends through sacral segments S4-5 C Incomplete Motor function below the neurological level, and the majority of key muscles have a muscle grade < 3. D Incomplete Motor function is preserved below the neurological level. Most key muscles below this level have a muscle grade ≥ 3. E Recovery Motor and sensory function is normal

 HUMAN SPINAL CORD INJURY: NEW & EMERGING THERAPIES  OVERVIEW: SCI ANATOMY & PHYSIOLOGY