Spinal Control of Movement (Ekman Ch 12) PDF

Spinal control of movement Ekman ch 12 Course: Neuroscience Dr. Meeyoung Kim Physiotherapy Dept. University of Sharjah Contents Anatomy Reflexes Spinal cord injury  Terminates at L1/2 vertebral level Spinal Cord Anatomy...

Spinal control of movement Ekman ch 12 Course: Neuroscience Dr. Meeyoung Kim Physiotherapy Dept. University of Sharjah Contents Anatomy Reflexes Spinal cord injury  Terminates at L1/2 vertebral level Spinal Cord Anatomy (conus medullaris) Dura extends to S2 vertebral level Filum terminale – fibrous Denticulate ligaments – Conus medullaris – terminal extension of the pia mater; delicate shelves of pia portion of the spinal cord anchors the spinal cord to mater; attach the spinal the coccyx cord to the vertebrae Spinal nerves – 31 pairs attach to the cord by paired roots Cervical and lumbar Cauda equina – collection enlargements – sites where of nerve roots at the Cervical nerves are named for inferior vertebra nerves serving the upper inferior end of the vertebral All other nerves are named for and lower limbs emerge canal superior vertebra Cross-Sectional Anatomy of the Spinal Cord Anterior median fissure – separates anterior funiculi Posterior median sulcus – divides posterior funiculi Structures - Spinal Cord Paired denticulate ligaments: extend from pia mater to dura mater stabilize side-to-side movement Blood vessels: along surface of spinal pia mater within subarachnoid space  Cross-sectional anatomy Gray matter (cell bodies, neuroglia, & unmyelinated processes) Posterior horns (sensory, all interneurons) Lateral horns (autonomic, T1-L2) Anterior horns (motor, cell bodies of somatic motor neurons) Spinal roots Ventral (somatic & autonomic motor) Dorsal (DRG: dorsal root ganglion)  Gray Matter: Organization Dorsal half – sensory roots and ganglia Ventral half – motor roots Dorsal and ventral roots fuse laterally to form spinal nerves Four zones are evident within the gray matter – somatic sensory (SS), visceral sensory (VS), visceral motor (VM), and somatic motor (SM)  White Matter in the Spinal Cord Fibers run in three directions – ascending, descending, and transversely Divided into three funiculi (columns) – posterior, lateral, and anterior Each funiculus contains several fiber tracts Fiber tract names reveal their origin and destination Fiber tracts are composed of axons with similar functions Pathways decussate (cross-over) Most consist of two or three neurons Most exhibit somatotopy (precise spatial relationships) Pathways are paired (one on each side of the spinal cord or brain)  White Matter: Pathway Generalizations dorsolateral system: voluntary movement in limbs includes reticulospinal tract + rubrospinal tract dorsal column pathway carry cognitive proprioception and light touch lateral has decessation at medulla and is bigger carry unconcious proprioception carry pain and temp has 2 tracts eye reflex remember location of: corticospinal tract rubrospinal tract rubrospinal tract helps corticospinal tract and all of ascending assists motor function (UL proximal) reticulospinal tract: coordination and balance ventromedial system: balance and trunk Remember the arrangement- White matter! Spinal Reflexes  5 components of a reflex arc we need those 5 components in order to have a reflex 1. Receptor 2. Sensory neuron info goes through dorsal root into the spinal cord 3. Integration center (CNS) 4. Motor neuron 5. Effector  passive stretch active stretch for a long time has 1B fiber  min 36-37 ! 1A: slim and fat- function is catching rate of change in length + length detection 2: connected to slim one (chain fiber)- function is length detection  1) Stretch Reflex agonist ms spindle ! inhibitory interneuron Reciprocal Inhibition antagonist For flexor reflex to work: the stretch reflex of antagonistic (extensor) muscle must be inhibited (reciprocal inhibition) by interneurons in spinal cord quads contract hamstring (antagonist) would be relaxed  Alpha – Gamma coactivation always activated together!! in order to keep sensitivity to occur relfex  2) Deep (Golgi) tendon reflex = Inverse stretch reflex The Golgi tendon organs sense excessive force in the tendon. They send signals to the spinal cord through sensory nerves. The spinal cord activates inhibitory interneurons that reduce the activity of the muscle (causing relaxation) and may activate its antagonist muscle. Comparison of function of muscle spindle and GTO  3) Withdrawal Reflexes Move body part away from stimulus (pain or pressure): e.g., flexor reflex: pulls hand away from hot stove 4) Crossed Extensor Reflexes Occur simultaneously, coordinated with flexor reflex Intersegmental reflex e.g., flexor reflex causes leg to pull up: crossed extensor reflex straightens other leg to receive body weight and it maintained by reverberating circuits A painful stimulus activates sensory receptors. The sensory signal travels to the spinal cord. Dual response: Ipsilateral side (same side): Activates motor neurons to flex the affected limb. Contralateral side (opposite side): Activates motor neurons to extend the opposite limb. CUTANEOUS REFLEXES PROVIDE PROTECTIVE AND POSTURAL FUNCTIONS Painful cutaneous stimulus transmitted by A afferent fibers induces contraction of flexor muscles in the stimulated limb and inhibition of opposing extensor muscles The stimulus also induces contraction of extensor muscles on the opposite limb, as a reflexive posture-correcting measure Spinal pathways are polysynaptic, utilizing various spinal interneurons Opposing effects on counteracting muscles for a joint referred to as reciprocal innervation Spinal Cord Injury  Spinal Cord Injury ASIA Impairment scale used for spinal cord injury classification graded from A to E criteria: we are checking at S4-5 A is complete injury of spinal cord (worst) Complete (A) – lack of motor/sensory function in sacral roots (S4-5) Incomplete (B) – sensory preservation, motor loss below injury including S4-5 Incomplete (C) – motor preservation below injury, more than ½ muscle groups motor strength 3 = or more than fair grade Normal (E) – all motor/sensory function present Cord Syndromes related to degenerative changes in spinal cord 1) Central Cord Typically fall with hyperextension esp of cervical spine Elderly degenerative changes Decreased strength corticospinal Decreased pain and temperature sensation spinothalamic Variable bowel and bladder dysfunction (Maintain bladder and bowel control) Spastic paraparesis/quadriparesis Prognosis: GOOD Although fine motor recovery of the upper extremities is rare  Cord Syndromes due to second neuron crossing over  Cord Syndromes 2) Anterior Cord Causes Direct injury to anterior spinal cord Primarily a hyperflexion mechanism Flexion injury of cervical spine causing a cord contusion Bony injury causing secondary cord injury Thrombosis of anterior spinal artery  Cord Syndromes Symptoms Anterior segment of spinal cord controls motor function below the injury Damage to the corticospinal and spinothalamic tracts Dorsal column function is intact Loss of: Motor function (Complete paralysis below the level of the lesion with loss of pain and temperature sensation) Pain and temperature sensation Vibration, position and crude touch are maintained function of dorsal column- but dorsal column is not involved  Cord Syndromes 3) Brown-Sequard Caused by: Penetrating injury (Hemisection of the cord) Lateral cord compression from: Disk protrusion Hematomas Bone injury Tumors Ipsilateral loss of: corticospinal tract Motor function Proprioception and vibration sense left or right Contralateral loss of: spinothalamic tract function Pain and temperature sensation Prognosis: GOOD  Cord Syndromes 4) Conus Medullaris L1-2 Presents secondary to disc herniation, spinal stenosis, or a compressive mass at the conus medullaris. may have L1 fracture not able to empty the bladder Areflexic bowel and bladder, flaccid anal sphincter Variable lower extremity loss 5) Cauda Equina Injury to the lumbosacral nerve roots often produced from fracture/disloc ations Areflexia Variable motor and sensory loss in lower extremities Sciatica Bowel and bladder dysfunction Saddle anaesthesia Any questions?