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Spinal Cord Organization. January 9, 2008. Spinal Cord 31 segments terminates at L1-L2 special components - conus medularis - cauda equina no input from the face. Spinal Cord, Roots & Nerves. Dorsal root. Ventral root. Spinal nerve. Dorsal Root Ganglion.

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Spinal Cord Organization

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Spinal Cord Organization

January 9, 2008


Spinal Cord 31 segments terminates at L1-L2 special components - conus medularis - cauda equina no input from the face


Spinal Cord, Roots & Nerves

Dorsal root

Ventral root

Spinal nerve


Dorsal Root Ganglion

Cell bodies of 1st order sensory neurons

Afferent


Spinal Cord Cross Section

Dorsal root

sensory

afferent

motor

efferent

Ventral root


Cross Section of Spinal Cord

White matter

peripheral

Gray matter

central

Central canal


Volume of Gray & White Matter

Gray matter enlarges at cervical and lumbar regions.

White matter increases at higher levels of the cord.


Central Gray Matter

Motor neurons

2nd order sensory neurons

Interneurons

Glial cells

Motor neuron = lower motor neuron

= anterior horn cell

= second order motor neuron


Organization of Gray Matter

Pain

Temperature


Organization of Gray Matter

Position sense

Vibration

Pressure

Touch


Organization of Gray Matter

Position sense

from legs

Between T1 and L2 enlarged

Dorsal nucleus of Clarke

2nd order sensory neuron going to cerebellum

Neck & base of Posterior Horn


Organization of Gray Matter

Interomedio-lateral horn

Between T1 and L2 enlarged

Sympathetic neurons

(preganglionic)

Intermediolateral Horn


Sympathetic Innervation


Organization of Gray Matter

.

At S2, S3, and S4

Parasympathetic neurons

(preganglionic)

Intermediolateral Horn


Parasympathetic Innervation


Organization of Gray Matter

Modulates motor activity via gamma motor neurons

Adjusts briskness of deep tendon reflexes


Organization of Gray Matter

Nuclei of alpha and gamma motor neurons

Innervates muscle spindles and muscles


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


Somatotopic Organization


Coordinating Role of Interneurons


Breathing

Nuclei of alpha and gamma motor neurons

LMNs from spinal levels C3, C4 & C5 innervate the phrenic nerve

Controls diaphragm


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


Sacral cord


Configuration of Gray Matter

Abundant white matter high in the spinal cord

Enlargement of gray matter at the cervical level

Innervates arm muscles


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


Descending Motor Pathway

Upper motor neuron

1st order neuron

synapses on LMN

Crossed pathway

Lateral corticospinal

Uncrossed pathway

Anterior corticospinal


Somatotopic Organization


Spinal Cord Tracts

Unconscious position sense

movement

feedback


↑ 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

Ascending & Descending Tracts


Ascending Tracts

Sensory

Position Vibration

Sensory

Pain Temperature


Spinal Cord Injury

Position

Pain

Brown – Sequard Syndrome


Transverse vs Hemi Cord Syndrome


Anterior vs Posterior Cord Syndromes


Blood Supply to Spinal Cord


Traumatic Spinal Cord Injury

DUI: $100 addt’l fine

South Carolina

Spinal Cord Injury

Research Board


Monday

Brainstem


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