6. Spinal Cord
Part of the CNS
About 18 Inches (45 cm) long in male, and 43
cm in female with the diameter of ¾(2 cm)
Extends from the foramen magnum to the end
of L1 (adults) and L3-L4 (infants)
Main pathway for information flow to and from
the brain
Spinal cord is made up of a core of gray matter
surrounded by white matter
9. Meninges of Spinal Cord
Pia mater (pia=delicate,mater=mother)
(deep)
◦ delicate
◦ highly vascular,Adheres spinal cord tissue
Arachnoid mater (arachne=spider) (middle)
◦ impermeable layer = barrier
Spinal Dura Mater (dura=tough)
(most superficial)
◦ single dural sheath
Subarachnoid Space
◦ between arachnoid and pia mater
◦ contains CSF
Epidural Space
◦ Between dura mater and vertebra
◦ Contains fat and veins
Subdural space
Between dura and arachnoid mater
11. Cross Section of Spinal Cord
Anterior median fissure
and posterior median
sulcus
◦ deep clefts partially
separating left and right
halves
Gray Matter
◦ “H” shaped Inner core
◦ Gray Commissure =
crossbar of “H”
◦ Central Canal = in gray
commissure
◦ Posterior/Dorsal horns
◦ Anterior/Ventral horns
Composed of
◦ Cell bodies
◦ Unmyelinated axons
◦ Dendrites
◦ Neuroglia
12.
13. Gray Matter
Posterior Horn is made up of interneurons which transmit
information from cell bodies situated outside of spinal cord
into the spinal cord.
◦ Dorsal Root contains Sensory Fibers
Somatic Sensory (SS)
Visceral Sensory (VS)
◦ Dorsal Root Ganglia-swelling in the dorsal root through which
these interneurons pass.
Anterior Horn is made up of cell bodies of motor neurons
that send axons out of spinal cord to muscles and glands.
◦ Ventral Root contains Motor Fibers
Visceral Motor
Somatic Motor
14. Nuclei of spinal cords
Nuclei in Anterior Gray Horn: The nuclei in the anterior horn innervate the skeletal
muscles. The nuclei of anterior horn are divided into 3 groups.
Medial Group : Present throughout entire extent of spinal cord & innervates axial
muscles of the body
Lateral Group: is present in cervical & lumbar enlargements & supplies
musculature of limbs. It is further divided into 3 subgroups:
(a) Anterolateral supplying proximal muscles of limb [shoulder & arms / gluteal
region & thigh]
[b] Posterolateral supplying intermediate muscles of limbs [forearm / leg]
[c] Post posterolateral: innervates distal segment {hand / foot]
Central Group: Only in cervical region as phrenic nerve nucleus and nucleus of
accessory nerve
15.
16. Nuclei in Lateral column
Inter mediomedial nucleus
Intermediolateral nucleus
Nuclei in Posterior column
Posteromarginal Nucleus : Thin Layer of neurons
1. Substantia Gelatinosa: acts as relay station for pain & temperature fibres & gives
rise to lateral spino-thalamic tract.
2. Nucleus Proprius : Concerned with sensory associative mechanism
3. Nucleus Dorsalis : Also k/s Thoracic nucleus. It relays nuclear column for reflex
or unconscious proprio-ceptive impulses to cerebellum & its axons give rise to
spino-cerebellar tract
17. White Matter
◦ Surrounds gray matter
◦ White columns
Posterior funiculus
Anterior funiculus
Lateral funiculus
◦ Axons in white matter are:
Myelinated axons
Unmyelinated axons
Function: Allows communication between parts of spinal cord, and between brain
+ spinal cord
Two main types of nerve fibers
◦ Ascending: carry SENSORY info from body to brain
(eg) touch, pressure, pain, temperature,
◦ Descending: carry MOTOR info from brain to spinal cord
(eg) control precise, skilled movement = writing, maintain balance, create
movement
18. Tracts in Spinal Cord
Group of nerve fibres passing through spinal cord are k/s Tracts. They
are divided into two main groups:
1 . Short tracts : Fibers of this tracts connect fibers of spinal cord
itself.
[a] Association or intrinsic tracts which connect adjacent segments of
spinal cord on the same side.
[b] Commissural tracts which connect opposite halves of same segment
of spinal cord.
2. Long tracts : Also k/s Projection tracts. They connect the spinal
cord with other parts of CNS. They are of 2 types:
[a] Ascending tracts
[b] Descending tracts
20. Ascending (afferent) spinal tracts
• Pathways that carry sensory information to a conscious level
Basic principle of information flow:
• receptor
(e.g. pain receptor in skin)
• primary sensory neurone
(cell body in dorsal root ganglia)
• second order neurone
(in the spinal cord or brainstem)
• third order neurone
(in thalamus)
• target area: cortex
somatosensory (somatic sensory) area
(postcentral gyrus) of the cortex
Note:- All the ascending tracts are formed by second order neuron except posterior white
funiculus which are formed from first order neuron
21. Major Sensory or Ascending Tracts
Name Location Function
Fasciculus
gracilis
Posterior
Column
Discriminative touch,
proprioception
Weight discrimination
Fasciculus
Cuneatus
Posterior
Column
Same as FG
Lateral
Spinothalamic
Lateral
Column
Pain and Thermal
sensations
Anterior
Spinothalamic
Anterior
Column
Itch, Tickle, Pressure,
Crude touch sensations
Posterior and
Anterior
Spinocerebellar
Lateral
Column
Proprioceptors
22. Anterior spinothalamic tract: Crossed ,
Unilateral lesion Loss of crude touch in opposite side, B/L lesion loss of crude
touch & sensations like itching & tickling both sides.
Lateral spinothalamic tract : Crossed,
Unilateral lesion Loss of pain & temp. sensation in opposite side below the level
of lesion , B/L lesion loss of pain & temp.sensations on both sides below the level of
lesion
Ventral Spinocerebellar tract : k/s Grower tract ,Crossed
Lesion leads to loss of subconscious kinesthetic sensations in the opposite side.
Dorsal Spinocerebellar tract: Uncrossed,
Unilateral loss of the subconscious kinesthetic sensations on the same side
Spinotectal tract: Crossed,
Concerned with spinovisual reflex
Fasciculus Dorsolateralis: k/s tract of lissauer, Uncrossed.
Carries impulses of pain & thermal sensations
Spinoreticular tract: Crossed
Components of ascending RAS, concerned with consciousness and awareness
23. Spino- Olivary tract : Crossed
Concerned with proprioception
Spinovestibular tract :
Concerned with proprioception
Fasciculus Gracilis (Tract of Goll ] And
Fasciculus Cuneatus [Tract of Burdach] :Uncrossed ,
Loss of tactile sensation, localization, point discrimination, vibrations,
astereognosis,proprioception,Sensory ataxia on the same side below the lesion
Comma tract of Schultze :
To establish intersegmental communications and to form short reflex arc.
26. Descending tracts
They are formed by nerve fibers arising from the brain and decend into the spinal cord.
They carry motor impulses from brain to the spinal cord. They are of 2 types:
[1] Pyramidal Tracts: Also k/s Corticospinal tract which descend from cerebral cortex to
spinal cord. They are concerned with voluntary movements of the body and are
responsible for fine skilled movements. They form upper motor neurons. There are 2
coticospinal tracts :-
Anterior corticospinal tract, Crossed &
Lateral corticospinal tract, Uncrossed
Effects of lesion at different level:
Cerebral cortex: Causes hypertonia, spasticity & contralateral monoplegia or
contralateral hemiplegia
Internal capsule: Contralateral hemiplegia
Brainstem: Contralateral hemiparesis along with VI and VII nerve palsies,
Spinal cord: Unilateral lesion in upper cervical region ipsilateral hemiplegia B/L
lesion causes quadriplegia with paralysis of respiratory muscles
27. B/L lesion of these fibres in thoracic and lumbar region causes paraplegia with
paralysis of respiratory muscles.
Extrapyramidal tracts:
Medial longitudinal fasciculus: Uncrossed
Lesion affects reflex ocular & reflex neck movements
Anterior & Lateral Vestibulospinal tract: Uncrossed
Lesion affects muscle tone & posture, adjustment of position of head & body
becomes difficult during acceleration
Reticulospinal tract: Uncrossed
Lesion causes disturbances in respiration, B.P , movements of body & muscle
tone
Rubrospinal tract: Crossed
They exhibit facilitatory influence upon flexor muscle tone.
Tectospinalspinal tract: Crossed
It is responsible for movement of head in response to auditory & visual reflex.
Olivospinal tract: Uncrossed
Invoved in reflex movements arising from proprioreceptors.
28.
29. Spinal Nerves (31 pairs)
Each pair of nerves located in particular segment
(cervical, thoracic, lumbar, etc.)
Each nerve pair is numbered for the vertebra sitting
above it (i.e. nerves exit below vertebrae)
◦ 8 pairs of cervical spinal nerves; *C1-C8
◦ 12 pairs of thoracic spinal nerves; T1-T12
◦ 5 pairs of lumbar spinal nerves; L1-L5
◦ 5 pairs of sacral spinal nerves; S1-S5
◦ 1 pair of coccygeal spinal nerves; C0
30.
31. Nerve Plexuses
Ventral rami (branches)
of various spinal nerves
blend together to form
an interwoven network
of nerves, nerve plexus
Four major plexuses
◦ Cervical
◦ Brachial
◦ Lumbar
◦ Sacral
32. Cervical plexus
Ventral rami of C1-C4 with a few fibers from C5
Innveration of muscles of the neck, shoulder and upper breast
Phrenic nerve – innervation of diaphragm
Brachial plexus
Axillary nerve
Radial nerve
Musculocutaneous nerve
Median nerve
Ulnar nerve
36. Spinal Cord Trauma and Disorders
• Severe damage to ventral root results in flaccid paralysis
• Skeletal muscles cannot move either voluntarily or involuntarily
• Without stimulation, muscles atrophy.
• When only UMN of primary motor cortex is damaged
• Spastic paralysis occurs - muscles affected by persistent spasms and exaggerated
tendon reflexes
• Muscles remain healthy longer but their movements are no longer
subject to voluntary control.
• Muscles commonly become permanently shortened.
• Transection (cross sectioning) at any level results in total motor and
sensory loss in body regions inferior to site of damage.
• If injury in cervical region, all four limbs affected (quadriplegia)
• If injury between T1 and L1, only lower limbs affected (paraplegia)
•Spinal shock - transient period of functional loss that follows the injury
• Results in immediate depression of all reflex activity caudal to lesion.
• Bowel and bladder reflexes stop, blood pressure falls, and all muscles (somatic and
visceral) below the injury are paralyzed and insensitive.
• Neural function usually returns within a few hours following injury
38. Spinal Cord Trauma and Disorders
•Amyotrophic Lateral Sclerosis (aka, Lou Gehrig’s disease)
• Progressive destruction of anterior horn motor neurons and fibers of the
pyramidal tracts
• Lose ability to speak, swallow, breathe.
• Death within 5 yrs
• Cause unknown (90%); others have high glutamate levels
• Poliomyelitis
• Virus destroys anterior horn motor neurons
• Victims die from paralysis of respiratory muscles
• Virus enters body in feces-contaminated water (public swimming pools]
•Syringomyelia
• Dilatation in central canal of spinal cord mainly in cervical region.
• Decussating fibres of pain and temp are affected but touch and
proprioception is present
39. Upper Motor Neuron (UMN) vs Lower Motor Neuron (LMN)
Syndrome
UMN syndrome LMN Syndrome
Type of Paralysis Spastic Paresis Flaccid Paralysis
Atrophy No (Disuse) Atrophy Severe Atrophy
Deep Tendon Reflex Increase Absent DTR
Pathological Reflex Positive Babinski Sign Absent
Superficial Reflex Absent Present
Fasciculation and Absent Could be
Fibrillation Present
