Download Spinal Cord

Spinal Cord
J‐H, Lue
1. General somatosensory (GSA), viscerosensory (GVA) fibers
2. General somatic and visceral motor neurons (GSE, GVE)
3 Descending tracts that influence the activity of spinal neurons
3.
4. Spinal reflex
1
I. Location and rostrocaudal extent
1. Spinomedullary junction
(foramen magnum )  Conus
medullaris (L.V.1 or L.V.2)
(45cm, 30g)
2. Cauda equina: compose of
lumbosacral roots which
suspend in subarachnoid
space
3. Filum terminale
i t
internum
f
from
conus
medullaris to S.V.2
2
Spinomedullary junction (foramen magnum )
Conus medullaris (L.V.1 or L.V.2) (45cm, 30g)
Spinal meninges
1.
Pia mater
Denticulate ligaments: pia+ arachnoid tissue, 21
pairs
Subarachnoid space: cerebrospinal fluid
Lumbar cistern : between L.V.2 and S.V.2 ;
lumbar puncture: L.V.3
L V 3 and L.V.4,
L V4
2. Arachnoid
3. Dura
mater
mater
Filum terminale externum (coccygeal ligament):
f
from
S
S.V.2
V 2 to coccyx
3
Spinal cord segments and spinal nerves
1. Unsegmented structure
intrinsically; but 31 external segments: 8
cervical, 12 thoracic, 5 lumbar, 5 sacral
and 1 coccygeal segments
2. In transverse with the spinal cord varies,
gradually tapering craniocaudally, except
at the level of the enlargement
3. Cervical enlargement
g
(C4-T1)
 brachial plexus
4. Lumbosacral enlargement
(L1 S2)  lumbosacral
(L1-S2)
l b
l plexus
l
4
1. Ventral
median
fissure: branch of ant. spinal
artery,
t
pia
i matter
tt
2. Dorsal median sulcus:
d
dorsal
l septum,
t
pia
i matter
tt
3. Ventrolateral sulcus
ventral roots leave region
4 Dorsolateral sulcus
4.
dorsal roots enter zone
5. Dorsal (posterior) intermediate sulcus :
between the gracile and cuneate fasciculus
5
Dorsal (posterior) horn
Intermediate zones Lateral horn
Ventral (anterior) horn
Gray commissure: surround the central
canal
6
C
Component
t
Intermediate zones
Lateral horn
Tract cell
Motor
Motor neuron
Interneuron
Neuroglia
7
Neuronal architecture of spinal gray matter
Laminar organization (Rexed
(Rexed’ss laminae)
Laminae I-IV: the head of dorsal horn
Laminae V-VI: the base of dorsal horn
Laminae VII: intermediate zone
Intermediolateral cell column (T1 to L2)
Sacral autonomic nucleus (S2 to S4)
Laminae VIII-IX: ventral horn
Laminae X: surround the central canal
8
Lamina IX (motor neuron)
Spatial organization
F
E
P
Proximal-distal rule
Flexor-extensor rule
•
•
•
•
Proximali l medial
di l group
Distal- lateral group
Extensor musclel ventrall group
Flexor muscle- dorsal group
9
10
Cl ifi i off somatic
Classification
i dorsal
d
l root fibers
fib
Number
Diameter (m)
Examples of receptors
Letter equivalent
Ia
12-20
annulospinal ending of
muscle spindle
A
Ib
12 20
12-20
Golgi tendon organ
A
II
6-12
A, A
III
1-6
flower spray ending of
muscle
l spindle;
i dl touch;
h
pressure
pain; temperature
p
p
A
IV
0.5-1.5
pain; temperature
C
11
Division of dorsal rootlet
Lateral division (group III and IV fibers) dorsolateral tract (of Lissauer)
M di l division
Medial
di i i (group
(
I and
d II fib
fibers)
) dorsal
d
l funiculus
f i l
12
Nerve fibers

White matter
Tract

Fasciculus

Funiculus
Dorsal funiculus
Lateral funiculus
Dorsolateral funiculus
Ventral funiculus
Ventrolateral funiculus
13
Dorsal funiculus
Gracile fasciculus: bellow T6
Cuneate fasciculus
discrimination touch,, vibratoryy
sense, and conscious muscle
joint sense
14
Lateral funiculus
Dorsolateral funiculus
Dorsolateral tract (of Lissauer):
situate between the tip of the dorsal
horn and dorsal root
15
Lateral funiculus
Dorsolateral funiculus
Posterior (dorsal) spinocerebellar
tract: locate
l t superficially
fi i ll between
b t
dorsolateral sulcus and denticulate
ligament; unconscious proprioception
16
Lateral funiculus
Dorsolateral funiculus
Lateral corticospinal tract:
medial to dorsal spinocerebellar tract
17
Corticospinal tract
18
Lateral funiculus
Dorsolateral funiculus
Rubrospinal fibers
19
Lateral funiculus
Ventrolateral funiculus
Ventral (anterior) spinocerebellar
tract: between denticulate ligament
and ventrolateral sulcus; unconcious
proprioception
20
Spinothalamic
p
tract
Lateral spinothalamic tract:
medial to ventral spinocerebellar
tract: pain, temperature
pathways
Ventral spinothalamic tract:
light touch and pressure
pathways
h
21
Ventral funiculus
• Medial longitudinal fasciculus
(MLF) (medial vestibulospinal tract)
• Lateral vestibulospinal tract
22
Ventral funiculus
Tectospinal tract: from
superior
i collicus
lli
23
Ascending tracts
24
Dorsal funiculus
Spinothalamic tract
25
Anterior
spinocerebellar
tract
Posterior
spinocerebellar
tract
26
Descending spinal tracts
27
Descending spinal tracts
• Lateral Pathways
– Corticospinal tract
• From motor cortex, via
int. capsule,
p
, cerebral
peduncle, decussate in
the medulla, pyramidal
tract
– Rrubrospinal tract
• From red nucleus
decussate in the pons
28
• The Ventromedial Pathways
– Vestibulospinal tract
• control neck and back muscles and thus guide head
movement
– Tectospinal tract
• direct the head and eye
y to move to appropriate
pp p
image
g
on the fovea
29
Regional characteristics
•Largest cross-sections are presented in the cervical and lumbar enlargements
•White substance decreases in progressively caudal sections
30
Spinal reflex
Tendon (knee-jerk, stretch)
reflex: monosynaptic reflex arch
Slight stretching stimulation
on muscle spindle
Ia sensory fiber
 motor neuron
stretched muscle contract
31
Nociceptive stimulation
Flexor (withdrawal, nociceptive)
reflex: polysynaptic reflex
III or IV dorsal root
excitatory or inhibitory interneurons
32
flexor or extensor  motor neuron
flexor muscle contract and extensor muscle relax
Spinal reflex
Crossed
extension
reflex :
Nociceptive stimulation
III or IV dorsal root
ipsilateral flexor excited and extensor inhibited
excitatory or inhibitory interneurons
33
contralateral flexor inhibited and extensor excited
Spinal cord
Dr. Lue J.-H. Neuroantomy
A. Organization of the spinal cord: an overview
1. Somatosensory (GSA), viscerosensory fibers (GVA)
2. Somatic and visceral motor neurons (GSE, GVE)
3. Spinal reflex
4. Descending tracts that influence the activity of spinal neurons
B. Gross features of the spinal cord and nerve roots
I. Location and rostrocaudal extent
1. Spinomedullary junction (foramen magnum ) Conus medullaris (L.V.1 or
L.V.2) (45cm, 30g)
2. Cauda equina: compose of lumbosacral roots which suspend in subarachnoid
space
3. Filum terminale internum from conus medullaris to S.V.2
II. Spinal meninges
1. Pia mater
a. Filum terminale internum: pia + neuroglia elements
*
Denticulate ligaments: pia-arachnoid tissue, 21 pairs
*
Subarachnoid space: cerebrospinal fluid;
Lumbar puncture: L.V.3 and L.V.4, lumbar cistern
2. Arachnoid mater
*
Subdura space: foramen magnum to the S.V.2
3. Dura mater
a. Dura sac: between L.V.2 and S.V.2
b. Filum terminale externum (coccygeal ligament): from S.V.2 to coccyx
*
Epidural space: between dura mater and periosteum, fatty tissue
III. Spinal cord segments and spinal nerves
1. Unsegmented structure intrinsically; but 31 external segments: 8 cervical, 12
thoracic, 5 lumbar, 5 sacral and 1 cocygeal segments
2. In transverse with the spinal cord varies, gradually tapering craniocaudally,
except at the level of the enlargement
3. Cervical enlargement (C4-T1) brachial plexus
4. Lumbosacral enlargement (L1-S2) lumbosacral plexus
IV. Fissure and sulci of the spinal cord
1. Ventral median fissure: branch of ant. spinal artery, pia matter
2. Dorsal median sulcus: dorsal septum, pia matter
3. Ventrolateral sulcus ventral roots leave region
1
4. Dorsolateral sulcus dorsal roots enter zone
5. Dorsal (posterior) intermediate sulcus : between the gracile and cuneate
fasciculus
C. Internal organization of the spinal cord
I. Gray matter: H shaped outline
*
Dorsal (posterior) horn
*
Ventral (anterior) horn
*
Gray commissure: surround the central canal
*
Intermediate zones
Lateral horn
* Component
* Tract cell
* Interneuron
* Motor neuron
* Neuroglia
1. Neuronal architecture of spinal gray matter
(1). Columnal organization
(2). Laminar organization (Rexed’s laminae)
 General
 Laminae I-IV: the head of dorsal horn
 Laminae V-VI: the base of dorsal horn
 Laminae VII: intermediate zone
 Intermediolateral cell column (T1 to L2)
 Sacral autonomic nucleus (S2 to S4)
 Laminae VIII-IX: ventral horn
 Lamina IX (motor neuron)


Spatial organization
 Proximal-distal rule
 Proximal- medial group
 Distal- lateral group
 Flexor-extensor rule
 Extensor muscle- ventral group
 Flexor muscle- dorsal group
 Interneurons
 Renshaw cells, glycine
Laminae X: surround the central canal
2

Lamina I
 Caps the tip of the dorsal horn



Posteromarginal nucleus
 Propriospinal tract
 Spinothalamic tract
Lamina II (substantia gelantinosa)

wealth of small neurons and unmyelinated fibers
Laminae III and IV






Nucleus proprius
 Spinothalamic tract
Laminae V and VI
 the base of the dorsal horn
lamina VI is present only in the enlargement
Lamina VII (intermediate zone)
 Intermediolateral cell column (T1 to L2)
 Sacral autonomic nucleus (S2 to S4)
 Clarke’s column (C8 to L3) dorsal spinocerebellar tract
Lamina VIII
 Dorsoventral direction (enlargement)
 Largest extent in thoracic levels
 Interneurons and propriospinal neurons
Lamina IX
 Motor neuron
 Alpha () motor neuron fiber (12-20m) extrafusal muscle
fibers
 Gamma () motor neuron fiber (4-8m) intrafusal muscle fibers
 Somatic motor cell columns
 Dorsolateral, ventrolateral, central column muscles of limb
 Ventromedial column (C1 to L4) muscles of neck & trunk
2. Dorsal root entry zone
 Classification of somatic dorsal root fibers
Number Diameter (m) Examples of receptors
Letter equivalent
Ia
12-20
annulospinal ending of
muscle spindle
A
Ib
II
12-20
6-12
Golgi tendon organ
flower spray ending of
muscle spindle; touch;
pressure
A
A, A
3
III
IV

1-6
0.5-1.5
pain; temperature
pain; temperature
A
C
Division of dorsal rootlet
 Lateral division (group III and IV fibers) dorsolateral tract (of
Lissauer)
 Medial division (group I and II fibers) dorsal funiculus
3. Chemoarchitecture
 Dorsal root
 Small diameter (group III and IV: substance P (SP), calcitonin generelated peptide (CGRP)
 Large diameter (group I and II): glutamate
 Dorsal horn
 Substance P, dopamine, GABA
 Ventral horn
 Serotonin, noradrenaline, Glycine(Renshaw cells)
 Motor function: ACh
II. White matter
1. Dorsal funiculus: discrimination touch, vibratory sense, and conscious muscle
joint sense
 Gracile fasciculus: bellow T6
 Cuneate fasciculus
2. Lateral funiculus
 Dorsolateral funiculus
 Dorsolateral tract (of Lissauer): situate between the tip of the dorsal
and dorsal root
 Dorsal (posterior) spinocerebellar tract: locate superficially between
dorsolateral sulcus and denticulate ligament; unconscious
proprioception
 Lateral corticospinal tract: medial to dorsal spinocerebellar tract
 Rubrospinal fibers
 Ventrolateral funiculus
 Ventral (aterior) spinocerebellar tract: between denticulate ligament
and ventrolateral sulcus; unconcious proprioception
 Lateral spinothalamic tract: medial to ventral spinocerebellar tract:
pain, temperature pathways
 Spinoreticular tract
 Reticulospinal fibers
4
3. Ventral funiculus
 Medial longitudinal fasciculus (MLF) (medial vestibulospinal tract)
 Ventral (anterior) spinothalamic tract: light touch and pressure
pathways
 Vestibulospinal tract
 Tectospinal tract: from superior collicus
 Ventral (anterior) corticospinal tract: uncrossed pyramidal tract
 Recticulospinal fibers
III. Regional characteristics
General
 Largest cross-sections are presented in the cervical and lumbar enlargements
 White substance decreases in progressively caudal sections
1. Sacral levels
 Small amount of white matter
 Substnatia gelainosa pronounced
 No dorsal spinocerebellar tract
2. Lumbar levels
 Enlarged cross-section area
 Lumbar enlargement (lateral group of motor)
3. Thoracic levels
 Gray matter reduced
 Lateral horn (intermediolateral nucleus): T1-L2
4. Cervical levels:
 Size increased
 Cervical enlargement (lateral group of motor)
V. Spinal reflexes
1. Tendon (knee-jerk, stretch) reflex: monosynaptic reflex arch
 Slight stretching stimulation on muscle spindle Ia sensory fiber 
motor neuron stretched muscle contract
2. Flexor (withdrawal, nociceptive) reflex: polysynaptic reflex
 Nociceptive stimulation III or IV dorsal root excitatory or inhibitory
interneurons flexor or extensor  motor neuron flexor muscle contract
and extensor muscle relax
3. Crossed extension reflex
 Nociceptive stimulation III or IV dorsal root excitatory or inhibitory
interneurons ipsilateral flexor excited and extensor inhibited
 contralateral flexor inhibited and extensor excited
5
D. Overview
1. Sensory neurons have cell bodies in the periphery and central processes that do
not cross the midline. Lower motor neurons have cell bodies in the central
nervous system and axons that do not cross the midline
2. Sensory pathways to the cerebral cortex involve a chain of at least three neurons,
the second having an axon that typically cross the midline.
3. Pathways serving conscious sensations are largely’crossed”.
4. Motor neurons project directly to skeletal muscle, whereas autonomic control
involves a two-neuron chain.
5. The stretch reflex involves only one synapse, whereas the flexor reflex involves
interneurons and multiple spinal cord segments.
E. Clinical notes
I. Dermatomes
 C3: Neck
 C5: Detoid region
 C6: Radial forearm and thumb
 C8: Ulnar border and little finger
 T4-T5: Nipple
 T10: Umbilicus
 L1: Groin
 L3: Knee region
 L5: Dorsal side of foot and great toe
 S1: Lateral side of foot and little toe
 S3-S5: Genito-anal region

Disc prolase
annulus fibrosus and posterior longitudinal ligament are degenerate
nucleus pulposus prolapsing in a posterolateral direction
 L4-L5 and L5-S1
 C5-C6 and C6-C7
 Herpes zoster: often in thoracic region
chickenpox virus causes inflammation of dorsal root ganglia
II Spinal cord disorders
 Tabes dorsalis: syphilitic infection of the dorsal root ganglia and dorsal roots
 Syringomyelia: softening and cavitation around the central canal
 Poliomyelitis: lesion of the ventral horns and ventral roots
 Amyotrophic lateral sclerosis: degeneration of lower and upper motor neurons

Brown-Sequard syndrome: spinal cord hemisecton
6