Nolte Chapter 10 – Spinal Cord
Dorsal is arrival(afferent), Ventral is exit(efferent) – Bell-Magendie law
Rostral to Caudal: Cervical, Thoracic, Lumbar, Sacral
There are two enlargements: cervical (upper extremities) and lumbosacral(lower extremities)
The caudal end of the cord is anchored to the end of the dural tube by the filum terminale
Gray matter is known as “horns” and white matter is known as “funiculi”
The thin zone of white matter connecting the two lateral halves is the anterior white commissure.
Motor neurons are in the anterior horns and their axons leave in the ventral roots.
Spinal Gray Matter
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Posterior Horn – Sensory Interneurons and Projection neurons
o contains the “body” and “substantia gelatinosa”
 substantia caps the posterior horn.
 between substantia and the surface of the cord is Lissauer’s tract which
contains finely myleinated and unmyelinated fibers
 the body consists of mainly interneurons and projection neurons.
Anterior horn – Motor neurons
o reffered to as lower motor neurons / alpha motor neurons
o destruction of these neurons causes paralysis of a muscle (flaccid paralysis) and leads to
atrophy.
o The clusters that innervate limb muscles are more lateral.
o fusimotor neurons innervate muscle spindles and are gamma motor neurons.
Spinal Accessory nucleus
o extends from caudal medulla to C5
o the axons emerge from the lateral surface of the spinal cord as rootlets that form the
accessory nerve.
Phrenic nucleus
o innervates the diaphragm and is located in the medial portion of the anterior horn.
Intermediate Gray
o contains autonomic neurons
o Clarke’s Nucleus
 on the medial surface of the base of the posterior horn
 a relay nucleus for the transmission of information to the cerebellum and
proprioceptive info from the leg to the thalamus.
o the whole body’s preganglionic sympathetic neurons are in T1-L3 in a column of cells
called the intermediolateral cell colum which forms a pointy lateral horn on the spinal
gray matter
Layers
o I – Marginal Zone
 thing layer of gray that covers the substantia gelatinosa
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II – Substantial Gelatinosa
III – VI – Body of the posterior horn
VII – intermediate gray area (including Clarke’s)
VIII – interneuronal sonzes of the anterior horn
IX – clusters of motor neurons in anterior horn
X – zone of gray matter surrounding the central canal
White Matter
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Can be either ascending, descending, or propriospinal (ineterconnecting different spinal cord
levels)
o propriospinal tract is a thin shell surrounding the gray matter
Medial Lemniscus (Posterior Column prior to decussation) – Touch and Limb Position
o information from low-threshold cutaneous joints and muscle receptors that reach the
cerebral cortex
 complex discrimination, proprioception, kinesthesia. damage causes atxia
(incoordination) which is largely pronounced when the eyes are closed.
 people that try to stand erect with their eyes closed show Romberg’s
sign.
o have their cell bodies in ipsilateral dorsal root ganglia
o There is a medial and alteral division
 medial is heavily myelinated
 lateral is finely myelinated.
o Caudal to T6 it is an individed bundle called the Gracile Tract
 because this is representing the lower part of the body only.
o Rostral to T6, the Cuneate Tract gets added laterally.
 keeps adding laterally as we move rostrally
o These synapse appropriately in the cuneate/gracile nucleus in the caudal medulla.
 after synapsing, the fibers cross the midline and form the medial lemniscus
o Visceral pain may travel between the gracile and cuneate.
o end up in the VPL
Spinothalamic Tract / Anterolateral Pathway conveys information about Pain and
Temperature
o Nociceptive, thermoceptive, and some mechanoreceptive fibers enter the spinal cord in
the lateral division of the dorsal root and project branches into the posterior horn.
o Synapse immediately onto Lamina I and project into substantial gelatnios
 send their axons across the midline immediately
 collaterals of the primary afferents may ascend one or more segments in
Lissauer’s tract before synapsing and then decussating and joining the
spinothalamic tract.
o the ones on their way to the reticular formation are just called spinoreticular and don’t
contain any somatotopic information, but are concerned with demanding attention to
pain.
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o destruction of this tract causes contralateral analgesia
o End up in VPL
Spinocervical tract
o conveys information from hair receptor and synapse on projection neurons in the
posterior horn
o terminates in the small lateral cervical nucleus and then cross the midline to join the
medial lemniscus and ascend to VPL
Spinocerebellar tracts
o this is the direct input to the cerebellum from the spinal cord.
o mechanoreceptive afferents will come along the gracile tract and then synapse on
Clarke’s nucleus(unless rostral to Clarke’s where they synapse on cuneate and become
the cuneocerebellar tract), whose cells give rise to the posterior spinocerebellar tract
 travels just lateral to the posterior horn
 enters the inferior cerebellar peduncle into the vermis.
 concerned with the ipsilateral leg
o the anterior spinocerebellar tract gets inputs from muscles and cutaneous and fibers of
descending tracts so it is related to “attempted” movement.
 crosses at the level of the spinal cord
 ascends to the rostral pons, cross again then turns caudally and enters in the
superior peduncle to the vermis and anterior lobe
 runs up lateral to the ventral horn.
o the rostral spinocerebellar tract is the forelimb equivalent and goes through both the
inferior and superior cerebellar peduncles.
Corticospinal tract mediates voluntary movement
o lateral corticopsinal tract / pyramid tract that originates in the precentral gyrus and
descends through the cerebral peduncle.
o in the spinal cord it is medial to the spinocerebellar tract
o ends in the anterior horn/intermediate gray matter to connect with alpha motor
neurons.
 upper motor neurons show that resting tension is increased and there can be
paralysis or weakness or spastic paralysis.
o there are 15% that don’t cross in the pyramids and just continue ipsilaterally
 this is the anterior corticospinal tract. They instead cross in the anterior white
commissure.
 most end in the cervical and thoracic segments to innervate the neck and
shoulder muscles.