The document summarizes the structure and function of the spinal cord. It discusses the following key points: - The spinal cord is approximately 45cm long in men and 43cm in women, and is protected by three meninges. It contains 31 segments that contribute nerves to different parts of the body. - Spinal nerves emerge from each segment and contain a dorsal root with sensory fibers and an anterior root with motor fibers. Ascending tracts transmit sensory information to the brain and descending tracts convey motor commands from the brain. - The principal ascending tracts are the posterior white column, anterolateral system, and spinocerebellar tract. The main descending tracts include the pyramidal,

2.  Structure
 Function
 Tracts

3. Long :-
 Men=45cm(18inch)
 Women=43cm(17inch)
Width :-
 Cervical and lumbar = 1/2inch thick
 Thoracic area = 1/4inch thick
 Begins from occipital bone until L1&L2
 the end of spinal cord = filum terminal

7.  Meninges
 Epidural = External of dura(fat-fil)
 Subdural space = Serous fluid
 Subarachnoid = Between pia and arachnoid (CSF filled)
Dura mater (dural
sheath)=outermost
Arachnoid’s mater =
thin,movable
Pia mater=forms filum
terminal,denticulate
ligament
Connective
tissue
membranes
Subdural
space
Subarachnoid
Epidural

9.  Spinal segment = spinal nerve
 Spinal nerve has two roots
 Dorsal root ganglion = swelling like structure
Anterior root= ventral root
Posterior root=dorsal root
SPINAL NERVE

12.  Spinal cord have 31 segment
8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
1 Coccygeal
 The spinal segments that contribute to the nerve
of the upper are enlargement to the form cervical
and lumbar enlargements

13. vertebrae spinal segments
C1 to C4 (upper cervical) same
C4 To C7 (lower cervical) +1
T1 to T7 +2
T7 to T9 +3
T10 L1,L2
T11 L3,L4
T12 L5,S1
L1 sacral and coccygeal nerve

20.  Spinal Arteries :-
 Anterior (1) & Posterior (2) Spinal Artery from
Vertebral artery
 Radicular Arteries :-
 Segmental arteries from Vertebral,Ascending
Cervical,Intercostal and Lumbar Artery
 Venous Drainage veins :-
 Longitudinal & Radicular Veins Intervertebral
veins Internal Vertebral Venous Plexus
external vertebral venous plexus segmental
veins

21.  Tract is a bundle of nerve fibers (within CNS)
having the same :-
 Origin
 Course
 Destination
 Function

23.  The name of the tract = origin
= destination
 The axons within each tract are grouped according
to the body region innervated
 Long tracts at white matter
 Short tracts at gray matter
 There are 2 types of tract :-
 Ascending tract
=Sensory
 Descending tract
=Motor

25.  Decussation is the cross-over of the tract
from one side to the other.
 Therefore,there are instances where the left
side of the body is controlled by the right
brain hemisphere.
 Decussation occurs at different locations for
each tracts.

30. Ascending Spinal Tracts

31.  Contain a sequence of 3 neurons
from the receptor to the cerebral
cortex
 1st order neuron:
Sensory neuron that delivers
information from the receptor to the
CNS.
 2nd order:
 Has cell body in the spinal cord or
medulla oblongata
 Axon decussate
 3rd order neuron:
 Has cell body in thalamus
 Axon terminates on cerebral
cortex ipsilaterally
1
2
3

32. Modality: Discriminative Touch
Sensation Conscious
Proprioception
Receptor: Most receptors except
free nerve endings
Ist Neuron: Dorsal Root Ganglion
(Spinal Ganglion)
Dorsal Column Nuclei (Nucleus
Gracilis
Thalamus (VPLc) ,Corona Radiata
Termination: Primary Somesthetic
Area (S I)
Posterior White Column-Medial
Lemniscal Pathway

33.  Modality:pain and thermal
sensations.
Ist Neuron : dorsal horn
 2nd Neuron: mostly in the
nucleus proprius), decussate
within one segment by passing
through the ventral white
commissure
 3rd Neuron: ventral posterior
nucleus of the thalamus
 Thalamic neurons project to the
somatosensory cortex

34.  Modality:non- discriminative
touch and pressure
 Ist Neuron : dorsal horn
 2nd Neuron: nucleus
proprius,crossing to opposite
side by passing through the
ventral white commissure
 3rd Neuron: in ventral
posterior nucleus of the
thalamus
 Thalamic neurons project to the
somatosensory cortex

35.  Ist Neuron neuron lie in base of
the dorsal horn of the lumbosacral
segments
 cross to opposite side, ascend as
far as the midbrain
 2nd Neuron: terminating in the
cerebellar cortex
Both spinocerebellar tracts convey
sensory information to the same
side of the cerebellum

36.  Info:Present only above
level L3
 Ist Neuron in Clark’s
column
 2nd Neuron: terminate
ipsilaterally in the
cerebellar cortex

38.  2 Sequence of neuron(from cerebral
cortex/brain stem – muscle)
 Upper Motor Neuron(UMN)
o Spinal cord -> brain
o Cell body cross over before terminate on lower
motor neuron
 Lower Motor Neuron(LMN)
o Spinal cord -> muscle
o Cell body pass through posterior root of spinal
nerve

39. DESCENDINIG
TRACT
PYRAMIDAL TRACT
(DIRECT)
ANTERIOR
CORTICOSPINAL
TRACT
LATERAL
CORTICOSPINAL
TRACT
EXTRAPYRAMIDAL
TRACT
(INDIRECT)
RETICULOSPINAL
TRACT
VESTIBULOSPINAL
TRACT
TECTOSPINAL
TRACT
RUBROSPINAL
TRACT

41. Function:voluntary movement
: fine skill movement
 Anterior corticospinal tract
o Origin:motor cortex (4,6)
:somatosensory cortex (1,2,3)
o Course:pass through midbrain(cerebral peduncle)
pyramid of medulla oblongata
o Termination: anterior white column

42.  Lateral corticospinal tract
o Origin: motor cortex (4,6)
:somatosensory cortex (1,2,3)
o Course: pass through midbrain(cerebral peduncle)
(cross over)
pyramid of medulla oblongata
o Termination: lateral white column
o Corticobulbar  innervate cranial nerves
 motor nuclei of CNS

47.  Function: coordination of voluntary and reflex
movement
: control of muscle tone
: control of respiration and diameter of
blood vessel
 Origin: Reticular formation (pontine & medulla)
 Course :pass through medial pontine
lateral medulla
 Termination: ventral funniculus

49.  Function: coordination of head and neck to
the visual & audio stimuli
 Origin : superior colliculus
 Course : pass through periaquductal
(cross)
Dorsal tegmental
 Termination: Anterior median fissure
(cervical area)

51.  Function : controls flexor
muscle tone
 Origin : Red nucleus
 Course :cross to
(lower cervical segment)
 Termination: lateral
white column

52.  Lateral vestibulospinal tract
 Function: control extensor
muscle tone
: antigravity
maintenance
of posture
 Origin : lateral vestibular
(Derter’s) nucleus
 Termination :ventral
funniculus

53. • Medial vestibulospinal tract
Function: control
movement
of head
:maintain
equilibrium
Origin:medial vestibular
nucleus
Termination: ventral
funniculus
+
medial
funniculus