Internal Anatomy Of The Spinal Cord Flashcards
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
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
Upper motor neurons origin
Start in higher centres (cortex)
UMNs send commands to ___
LMNs
Lesion to UMN leads to ____ or ____
Spastic paresis (hyperreflexia & hypertonia) or paralysis
LMN origin
Start in spinal cord (ventral horn cells) & brainstem (cranial nerve nuclei)
LMNs command
Directly command muscles to contract via spinal & cranial nerves
LMN lesion leads to ____
Flaccid paresis/paralysis (hyporeflexia & hypotonia)
Pericornual cells
Relay centre for pain & temperature
Substantia gelatinosa
Involved in ‘editing’ pain
- inhibits pain nuclei
Nucleus proprius
Contains cell bodies of neurons in several tracts
(Pain, temperature, tickle, itch)
Nucleus dorsalis (Clarke’s column)
C8-L2,3 only
Involved in proprioception of lower body
Intermediolateral cell column
T1-L2: preganglionic sympathetic neuron cell bodies
S2-4: preganglionic parasympathetic cell bodies
Motor nuclei (ventral horn cells)
Contain cell bodies of LMNs, both alpha & gamma, which innervate skeletal muscle
Cell columns in gray matter
- Pericornual cells
- Substantia gelatinosa
- Nucleus proprius
- Nucleus dorsalis
- Intermediolateral cell column
- Motor nuclei
Rexed Laminae I
Pericornual cells
Rexed Laminae II
Substantia gelatinosa
Rexed Laminae III-VI, part of VI
Nucleus proprius
Rexed Laminae VII
Intermediate zone, includes nucleus dorsalis & Intermediolateral column
Rexed Laminae VIII
Part of ventral horn, projections to lamina IX
Rexed Laminae IX
Motor nuclei
Rexed Laminae X
Ventral & dorsal gray commisures
Ascending pathways carry information from ____ to ____
Lower centres (or peripheral body) to higher centres
The first neuron in an ascending pathway is the ____
Primary afferent neuron
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
- Dorsal columns/medial Lemniscus: fasciculi gracilis & cuneatus
- spinocerebellar tracts
- 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
