Spinal Cord
J‐H, Lue
1. Somatosensory (GSA), viscerosensory (GVA) fibers
2. Somatic and visceral motor neurons (GSE, GVE)
3 Spinal reflex
3.
4. Descending tracts that influence the activity of
spinal neurons
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
Filum terminale internum: pia + neuroglia
elements
Denticulate ligaments: pia+ arachnoid tissue
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
Dura sac: between L.V.2 and S.V.2
Filum terminale externum (coccygeal ligament):
y
from S.V.2 to coccyx
Epidural space: between dura mater and
periosteum, fatty tissue
3
Spinal cord segments and spinal nerves
1 Unsegmented
1.
U
d structure intrinsically;
i i i ll but
b
31 external segments: 8 cervical, 12
thoracic, 5 lumbar, 5 sacral and 1
coccygeall segments
t
2. In transverse with the spinal cord varies,
gradually tapering craniocaudally, except
at the level of the enlargement
3. Cervical enlargement (C4-T1) 
b hi l plexus
brachial
l
4. Lumbosacral enlargement (L1-S2) 
lumbosacral plexus
4
1. Ventral median fissure:
branch of ant. spinal artery, pia
matter
2. Dorsal median sulcus: dorsal
septum pia matter
septum,
3. Ventrolateral sulcus
ventral roots leave region
4 Dorsolateral sulcus dorsal
4.
roots enter zone
5. Dorsal (posterior) intermediate sulcus :
between the gracile and cuneate fasciculus
5
Dorsal (posterior) horn
Intermediate zones
Ventral ((anterior)) horn
Gray
y commissure: surround the central canal
Lateral horn
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
•
•
•
•
Proximal- medial group
Proximal
Distal- lateral group
Extensor muscle
muscle- ventral 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
I
Ia
12 20
12-20
annulospinal
l i l ending
di off
muscle spindle
A
A
Ib
12-20
Golgi tendon organ
A
II
6-12
A, A
III
1-6
flower spray ending of
muscle spindle; touch;
pressure
pain; temperature
IV
0.5-1.5
pain; temperature
C
A
11
Division of dorsal rootlet
Lateral division (g
(group
p III and IV fibers)
) dorsolateral tract ((of Lissauer))
Medial division (group I and II fibers) dorsal funiculus
12
Nerve fibers

White matter
Tract

Fasciculus

Funiculus
Lateral funiculus
Dorsal funiculus
Ventral funiculus
Dorsolateral funiculus
Ventrolateral funiculus
13
Dorsal funiculus
Gracile fasciculus: bellow T6
Cuneate fasciculus
discrimination touch,
touch vibratory
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 superficially between
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 (anterior) spinothalamic
tract: light touch and pressure
pathways
21
Ventral funiculus
• Medial longitudinal fasciculus (MLF)
(medial vestibulospinal tract)
• Vestibulospinal tract
22
Ventral funiculus
Tectospinal tract: from
superior collicus
23
Ascending tracts
24
Dorsal funiculus
Spinothalamic tract
25
Anterior spinocerebellar
tract
Posterior spinocerebellar
t t
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
C
Crossed
d extension
t i reflex
fl :
Nociceptive stimulation
III or IV dorsal root
ipsilateral flexor excited and extensor inhibited
excitatory or inhibitory interneurons
33
contralateral flexor inhibited and extensor excited