3. SPINAL CORD
Brain and spinal cord are parts of the central
Nervous system , except them everything else
comes under P.N.S.
It performs two main functions
1 -conduction of impulses to and from the
brain
2 -it processes sensory information in a limited
manner, making it possible for the cord to
initiate stereotyped reflex actions ( spinal
reflexes with out input from higher centers in
the brain).
4. SPINAL CORD
Spinal cord weighs about 30 grams
, comprises 2% of the adult brain
weight
1 cm In diameter
Average length
45 cm in male
42 cm in female
5. SPINAL CORD
A. LOCATION
B.ATTACHMENTS
–denticulate ligaments Suspend and Anchor
the spinal cord within the DURAL SAC and
arises from the vascular pia matter
- filum terminale
-spinal nerve roots
8. GENERAL STRUCTURE OF
SPINAL CORD
Conus medullaris = Tip of spinal cord
filum terminale = a pial filament Extending from
C. medullaris to the end of dural sac. With
which it fuses.
Which extend up to the level of L1 and L2
31 pairs of mixed (motor and sensory ) spinal
nerves which passes through intervertebral
forminae except C1
9. GENERAL STRUCTURE OF
SPINAL CORD
Cervical nerves C1-C8
Thoracic nerves T1-T12
Lumbar nerves L1-L5
Sacral nerves S1-S5
Cocygeal nerve
10. GENERAL STRUCTURE OF
SPINAL CORD
Each portion of the cord that gives rise to a pair
of spinal nerves is called a spinal segment
At the end of spinal cord,the descending lumber
and sacral roots has the appearance of a
horse tail and therefore ---- cauda equina
Cervical enlargement ----- upper limb
(C5-T1) Brachial plexus
Lumber enlargment ------ lower limb
(L1-S2) Lumbo sacral plexus
11. SPECIAL CONSIDERATION
-The C1 and the cocceygeal nerves usually have
no dorsal (sensory) roots and no
corresponding dermatome
-C1 passes between the atlas and skull
-C2 between atlas and axis vertebrae
-All cervical spinal nerves passes above the
vertebrae
15. COMPONENTS AND BRANCHES
OF SPINAL NERVE
D. White communicating ramus contains
myelinated Preganglionic sympathetic fibers
and myelinated GVA
-are found only in THORACOLUMBER
segments of the spinal cord T1-L3
16.
17.
18. MENINGES
GREEK=membrane SINGULAR meninex
PIA MATTER
, LATIN=faithful, gentle, pious
ARACHNOID MATTER, GREEK=spider or
web
DURA MATTER, LATIN=tough
21. MENINGES OF THE SPINAL
CORD
ARACHNOID: mater forms a close lining of the dura
mater . The sub arachnoid space contains C.S.F.
It is largest in the region of the cauda equina.
PIA MATER contains a rich network of blood
vessels.
Spinal cord is held in a some what fixed position
with in the meninges by fibrous bridges that cross
the subarachnoid spaces joining pia mater
arachnoid and dura mater. The heaviest of the
bridges are the denticulate ligaments.
22. COMPOSITION OF SPINAL
CORD
Like brain spinal cord consists of areas of
white – myelinated processes of neurons
and gray – nerves cell bodies and unmyelinated
inter neuronal nerve fiber.
Neuroglia the supportive cells are present in both
white and gray mater.
In contrast to cerebrum and cerebellum the gray
mater is centrally located and is surrounded by
white mater.
Gray mater
Letter H or butterfly shape
23. COMPOSITION OF SPINAL
CORD
Gray commisure
Central canal is in the gray commisure
Posterior (dorsal) horns
Anterior (ventral ) horns
In thoracic and lumber regions (T1_L3)
Gray mater also include lateral horns.
24. COMPOSITION OF SPINAL
CORD
Alar plate consist of
post horns composed of axons of sensory
neurons of spinal nerve and inter neurons that
transmit sensory information.
27. COMPOSITION OF SPINAL
CORD
BASAL PLATE consist of
ANTERIOR HORN-somatic motor neurons.
Axon leaves the spinal cord and enter a spinal
nerve.
LATERAL HORN – visceral motor neurons
29. FUNCTIONAL COMPONENTS OF
A SPINAL NERVE
WHITE MATTER OF THE SPINAL CORD:
myelinated axons and travel in three direction
1- UP the spinal cord to higher level in the cord or
brain.
2-DOWN the spinal cord from the brain or higher
levels of the cord.
3-ACROSS the cord , transmitting impulses from
one side to the other.
white matter of each half of spinal cord is divided by
the gray matter into three areas
30. Post funiculus
Lateral funiculus
Ant funiculus
With in the funiculi there are small bundles of
nerve fibers called fasiculi = tracts.
A tract carry similar types of impulses to a
specific destination and are composed of the
conductive processes of neurons.
31. Ascending sensory = to brain
Descending motor = from brain down to the
motor neurons in the anterior or lateral gray
horns of spinal cord.
Most of the tracts have descriptive names that
indicate where they begin and where they
terminate.
Ascending spinal tract (sensory tracts)
These tracts of spinal cord carry afferent
(sensory)
32. Impulses from peripheral sensory receptors to
various centers in the brain.
These tracts generally contain three successive
neurons called
1st order (dorsal root ganglia)
2nd order (spinal cord or medulla)
3rd order (thalamus)
↓ ↓
cerebral cortex
35. Fasciculus gracilis
} proprioception fine touch
Fascilis cuneatus
lateral spinothalamic } pain and temperature
Ant spinothalamic } touch and pressure
37. Descending (motor ) spinal tracts
Brain lower motor neurons
That regulate the activity of skeletal muscles i.e
voluntary skilled motor activity (limbs)
All of these tracts cross form one side of CNS to
the other and they all contain two or three
consecutive neurons .
38. Two types of descending spinal tracts
1-pyramidal tracts
2-extra pyramidal tracts
60. 1-PYRAMIDAL TRACTS
Pyramidal tracts = corticospinal tract = uper motor
neurons
crossing at medulla to form lateral corticospinal
tract 80 % remaining 20 % form anterior
conticospinal tract which are uncrossed .
61.
62. The remaining motor tracts are called extra
pyramidal tracts
They begin from various nuclei in the brain stem
and influence
Muscular action
Co-ordination
Balance
Visual and auditory stimuli and other functions
64. Over lapping of corticospinal ad extra pyramidal
tracts clean separation is not possible.
Pyramidal spinal tract = movement of the body
Extra pyramidal spinal tract = posture and
balance and to modify muscular contraction.
