- sensory info goes into spinal cord via dorsal roots of spinal nerves - motor “commands” leave spinal cord via ventral roots of spinal nerves

Internal Anatomy Of The Spinal Cord Flashcards by Lindsay Kirkpatrick

Functions of Spinal cord

relay centre for incoming sensory info through dorsal roots & horn
conduit for ascending (afferent) & descending (efferent) pathways
origin of lower motor neurons “final common pathway of Sherrington” and thus “commands” to skeletal muscles of the body through ventral horns & roots

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Bell-Magendie Law

sensory info goes into spinal cord via dorsal roots of spinal nerves
motor “commands” leave spinal cord via ventral roots of spinal nerves

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Upper motor neurons origin

Start in higher centres (cortex)

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UMNs send commands to ___

LMNs

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Lesion to UMN leads to ____ or ____

Spastic paresis (hyperreflexia & hypertonia) or paralysis

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LMN origin

Start in spinal cord (ventral horn cells) & brainstem (cranial nerve nuclei)

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LMNs command

Directly command muscles to contract via spinal & cranial nerves

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LMN lesion leads to ____

Flaccid paresis/paralysis (hyporeflexia & hypotonia)

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Pericornual cells

Relay centre for pain & temperature

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Substantia gelatinosa

Involved in ‘editing’ pain
- inhibits pain nuclei

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Nucleus proprius

Contains cell bodies of neurons in several tracts
(Pain, temperature, tickle, itch)

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Nucleus dorsalis (Clarke’s column)

C8-L2,3 only
Involved in proprioception of lower body

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Intermediolateral cell column

T1-L2: preganglionic sympathetic neuron cell bodies
S2-4: preganglionic parasympathetic cell bodies

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Motor nuclei (ventral horn cells)

Contain cell bodies of LMNs, both alpha & gamma, which innervate skeletal muscle

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Cell columns in gray matter

Pericornual cells
Substantia gelatinosa
Nucleus proprius
Nucleus dorsalis
Intermediolateral cell column
Motor nuclei

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Rexed Laminae I

Pericornual cells

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Rexed Laminae II

Substantia gelatinosa

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Rexed Laminae III-VI, part of VI

Nucleus proprius

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Rexed Laminae VII

Intermediate zone, includes nucleus dorsalis & Intermediolateral column

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Rexed Laminae VIII

Part of ventral horn, projections to lamina IX

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Rexed Laminae IX

Motor nuclei

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Rexed Laminae X

Ventral & dorsal gray commisures

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Ascending pathways carry information from ____ to ____

Lower centres (or peripheral body) to higher centres

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The first neuron in an ascending pathway is the ____

Primary afferent neuron

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Functions of dorsal columns/medial lemniscus pathway

- vibration sense - conscious proprioception - discriminatory touch (fine touch) - stereognosis (3D knowledge)

Dorsal columns (dorsal funiculus) carry ____

Primary afferent neurons

Fasciculus gracilis: From ____ Ends in ____ Exits at ____

From ipsilateral lower body Ends in nucleus gracilis in medulla Exits at all spinal cord levels

Fasciculus Cuneatus: From ____ Ends in ____ Exits at ____

From ipsilateral upper body Ends in nucleus cuneatus of medulla Exits from T6 and above

Somatopy

Organization of many tracts, nuclei, and brain areas reflects the body’s organization - adjacent body parts are represented in adjacent parts of the tract, etc.

Spinocerebellar tracts carry ____ information

Proprioception

Spinocerebellar tracts carry proprioceptiive information from ____ to ____

From lower body to ipsilateral cerebellum

Lesion to Spinocerebellar tracts leads to ____

Ataxia (unsteady, wide gait)

Anterolateral system (spinolathamic tracts) 1° and 2° afferents run through….

- dorsolateral fasciculus - lateral spinothalamic tract

Dorsolateral fasciculus: - neuron type - cell body location - ____ to stimulus - ends in ____

- primary pain & temperature afferents - cell bodies in DRG - ipsilateral to stimulus - ends in ipsilateral nucleus proprius, 2 levels above where it entered SC

Lateral spinothalamic tract: - neuron type - cell body location - ____ to stimulus - ends in ____

- secondary pain & temp afferents - cell bodies in nucleus proprius - axons cross in ventral white commissure to enter lateral spinothalamic tract, becoming **contralateral** - ends in thalamus

Cervical spinal cord appearance

Bigger ventral horn (gray) More white matter

Thoracic spinal cord appearance

Distinct intermediolateral horn More white matter than lumbar

Lumbar spinal cord appearance

Larger ventral horn (gray) Less white matter

Pathway responsible for light and poorly localized/crude touch

Ventral spinothalamic tract

Ventral spinothalamic tract: - neuron type - _____ to sensation - ends in____

- secondary afferents - contralateral to sensation - ends in thalamus

Pathway responsible for pain & temperature

Anterolateral system (spinothalamic tracts)

White matter descending pathways

- Lateral Corticospinal Tract (LCST) - Ventral Corticospinal Tract (VCST)

LCST & VCST are both part of the ____

Corticospinal Tract (pyramidal tract)

LCST & VCST both contain ____ neurons mostly involved in _____ movement

UMN voluntary movement

Corticospinal fibers begin at the ____

Cerebral cortex

Corticospinal fibers proceed through….

Corona radiata Internal capsule Crus cerebri (midbrain) Basilar pons Pyramids of medulla

# LCST At the lower medulla ____% of fibers cross the pyramidal decussation and enter the lateral Corticospinal tract

85%

fibers that enter the LCST affect ____ muscles

Ipsilateral muscles

LCST fibers synapse onto ____MNs in the ____ horn

LMNs Ventral horn

LCST fibers effect…

Distal mostly flexor muscles

____% of fibers that do NOT cross the pyramidal decussation enter the Ventral Corticospinal tract

15%

Fibers of VCST cross in the ____

Ventral white commissure

Fibers of VCST synapse onto interneurons or directly onto ____

LMNs

VCST fibers effect…

Core musculature

Ascending pathways

- fasciculi gracilis & cuneatus - Spinocerebellar tracts - dorsolateral fasciculus & lateral spinothalamic tract (with ventral spinothalamic tract)

Descending pathways

- lateral Corticospinal tract - Ventral Corticospinal tract

Brown- sequard syndrome: lesion

Lesion of white matter on one side (hemisection)

Brown-sequard syndrome results in….

- loss of ipsi deep sensibility from level of lesion down (dorsal columns: FG, FC) - loss of contra P&T from 2 levels below lesion down (LSTT) - ipsi spastic paralysis from level of lesson down (LCST) - loss of proprioception from lower limb -> ataxia (Spinocerebellar Tracts) - ipsi loss of P&T at level of lesion and possibly 2 below (Dorsolateral fasciculus of Lissauer)

Syringomyelia

- expansion of central canal into spinal cord destroys ventral white commissure first, the progress laterally & dorsally - bilateral segmental loss of P&T 2 levels below lesion only

# general rule lesion above pyramidal decussation

contralateral

# general rule lesion below pyramidal decussation

ipsilateral

# general rule lesion to ventral root/horn (LMN)

flaccid paralysis

# general rule lesion to LCST

spastic paralysis

name the ascending pathways

1. Dorsal columns/medial Lemniscus: fasciculi gracilis & cuneatus 2. spinocerebellar tracts 3. Spinothalamic: dorsolateral fasciculus & lateral spinothalamic tract (with ventral spinothalamic tract)

motor neurons in dorsal ramus go to...

back

motor neurons in the ventral ramus go to...

front & extremities

pain in the neck or back travels through the ____ ramus

dorsal ramus

What lesions result in Brown-Sequard syndrome?

Lesion of white matter on one side: - dorsal columns: FG, FC - LSTT - LCST - Spinocerebellar tracts - Dorsolateral Fasciculus of lissauer