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Published byPiers Harrington Modified over 9 years ago
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Spinal Cord Organization January 9, 2008
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Spinal Cord 31 segments terminates at L1-L2 special components - conus medularis - cauda equina no input from the face
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Spinal Cord, Roots & Nerves Dorsal root Ventral root Spinal nerve
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Dorsal Root Ganglion Cell bodies of 1 st order sensory neurons Afferent
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Spinal Cord Cross Section Dorsal root sensory afferent Ventral root motor efferent
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Cross Section of Spinal Cord White matter peripheral Gray matter central Central canal
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Volume of Gray & White Matter Gray matter enlarges at cervical and lumbar regions. White matter increases at higher levels of the cord.
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Central Gray Matter Motor neurons 2 nd order sensory neurons Interneurons Glial cells Motor neuron = lower motor neuron = anterior horn cell = second order motor neuron
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Organization of Gray Matter Pain Temperature
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Organization of Gray Matter Position sense Vibration Pressure Touch
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Organization of Gray Matter Position sense from legs Between T1 and L2 enlarged Dorsal nucleus of Clarke 2 nd order sensory neuron going to cerebellum Neck & base of Posterior Horn
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Organization of Gray Matter Interomedio- lateral horn Between T1 and L2 enlarged Sympathetic neurons (preganglionic) Intermediolateral Horn
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Sympathetic Innervation
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Organization of Gray Matter. At S2, S3, and S4 Parasympathetic neurons (preganglionic) Intermediolateral Horn
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Parasympathetic Innervation
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Organization of Gray Matter Modulates motor activity via gamma motor neurons Adjusts briskness of deep tendon reflexes
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Organization of Gray Matter Nuclei of alpha and gamma motor neurons Innervates muscle spindles and muscles
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Lower Motor Neurons Alpha motor neurons originate from Rexed lamina IX ventral – dorsal organization ventral extensor muscles dorsal flexor muscles medial – lateral organization medial proximal muscles lateral distal muscles
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Somatotopic Organization
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Coordinating Role of Interneurons
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Breathing Nuclei of alpha and gamma motor neurons LMNs from spinal levels C3, C4 & C5 innervate the phrenic nerve Controls diaphragm
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Control Functions Nuclei of alpha and gamma motor neurons At levels S1 - S4 LMNs form Onuf’s nucleus Innervates anal and urethral spincters; needed for sexual function
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Sacral cord
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Configuration of Gray Matter Abundant white matter high in the spinal cord Enlargement of gray matter at the cervical level Innervates arm muscles
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Configuration of Gray Matter Enlargement in thoracic region for sympathetic neurons Enlargement in lumbar region for motor neurons to the legs Minimal white matter at the lower cord
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Descending Motor Pathway Upper motor neuron 1 st order neuron synapses on LMN Crossed pathway Lateral corticospinal Uncrossed pathway Anterior corticospinal
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Somatotopic Organization
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Spinal Cord Tracts movement feedback Unconscious position sense
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Ascending & Descending Tracts ↑ Sensory –Gracile tract Leg position & vibration –Cuneate tract Arm position & vibration –Dorsal spinocerebellar tract Strength & muscle speed –Ventral spinocerebellar tract Modulation; interneurons –Lateral spinothalamic tract Pain & temperature –Anterior spinothalamic tract Light touch –Spinocervical thalamic tract Kinesthetic movement & discriminative touch ↓ Motor –Corticospinal tract Speed & agility –Reticulospinal tract Differential facilitation of motor neurons –Rubrospinal tract Fix movement errors –Lateral vestibulospinal tract Extensor & posture –Medial vestibulospinal tract Flexor & head position –Tectospinal tract Head turning
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Ascending Tracts Sensory Position Vibration Sensory Pain Temperature
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Spinal Cord Injury Position Pain Brown – Sequard Syndrome
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Transverse vs Hemi Cord Syndrome
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Anterior vs Posterior Cord Syndromes
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Blood Supply to Spinal Cord
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Traumatic Spinal Cord Injury DUI: $100 addt’l fine South Carolina Spinal Cord Injury Research Board
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Monday Brainstem
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