spinal cord, ascending tracts of the the spinal cord, spinocortical tracts, gray matter of spinal cord, white mater of spinal cord, organization of neuron, first order second order and third order neuron, anterolateral spinal tract anteroposterior spinal tract, spinolivary tract, visceral sensory tract, dorsal column tract, spino cerebellar tract , spinorectal pathway, spino olivary pathway, cerebellar peduncles,

1. ASCENDING TRACTS
DR SANA YASEEN
ANATOMY DEPARTMENT

2. GREY MATTER OF SPINAL CORD
 In the spinal cord, gray mater is
centrally located.
 Its shape resembles a letter H or
a butterfly.
 The gray matter may be
subdivided into the following
components:
 anterior horns
 lateral horns
 posterior horns
 the gray commissure

3. WHITE MATTER OF SPINAL CORD
 myelinated (and unmyelinated) fibers carrying information (impulses) between brain
and spinal cord and from one level to another within spinal cord
 organized as white columns = funiculi
 dorsal (posterior) funiculus or columns
 ventral (anterior) funiculus
 lateral funiculus
 columns (funiculi) may contain both ascending and descending tracts
 A funiculus is a small bundle of axons (nerve fibres), enclosed by
the perineurium
 several funiculi collected together into larger bundles known as fasciculi

4. WHAT IS TRACT?
 A collection of nerve cell fibers
within the central nervous
system, that are segregated
and sorted into nerve bundles
or tracts in the white matter

6. ASCENDING SPINAL TRACTS
Transmit impulses:
 Concerned with specific sensory modalities: pain, temperature, touch,
proprioception, that reach a conscious level (cerebral cortex)
1. Dorsal column medial tracts
2. Spinothalamic tracts
 From tactile and stretch receptors to subconscious centers (cerebellum)
1. Spinocerebellar tracts

7. ASCENDING SPINAL TRACTS
 Dorsal white column
 Anterolateral spinothalamic
 Anterioposterior Spinocerebellar
 Cuneocerebellar
 Spinotectal
 Spinoreticular
 Spino-olivary
 Visceral sensory tracts

8.  Three major pathways carry sensory information
Dorsal/Posterior column pathway (gracile & cuneate fasciculi)
Anterolateral pathway (spinothalamic)
Spinocerebellar pathway

9. ANATOMICAL ORGANIZATION
Ascending pathway to consciousness
consist of 3 neurons
1. 1st order neuron…cell body in
posterior root ganglion of spinal
nerve. A peripheral process
connects with sensory receptor
ending where as central process
enters spinal cord through post
root to synapse on 2nd order
neuron

10. Cell body of 2nd
order neuron…in
spinal cord & its
axons always
decussate

11. Cell body of 3rd order
neuron:
always in thalamus…it gives
rise to projection fibers that
pass to sensory area of
cerebral cortex

13. DORSAL COLUMN – MEDIAL LEMNISCUS PATHWAY
FAST PAIN , DISCRIMINATIVE TOUCH, VIBRATION, PROPRIOCEPTION
 First Order Neuron:
 Cell body is in the posterior root ganglion (PRG)
 Axon ascends directly in posterior columns (fasciculus gracilis or fasciculus
cuneatus)
(input from Pacinian corpuscles,joint receptors,muscle spindles ,meissner’s
corpuscles, golgi tendon organ)

14.  Fasciculus gracilis is present
throughout the length of spinal
cord & contains long ascending
fibers from sacral, lumbar, &
lower six thoracic spinal nerves
 Fasciculus cuneatus is situated
laterally in upper thoracic &
cervical segments of spinal cord
& contains fibers from upper 6
thoracic & all the cervical spinal
nerves.

15.  Second Order Neuron:
 Cell body is in nucleus gracilis or
nucleus cuneatus in the medulla
 Axons of 2nd order neuron called
as internal arcuate fibers which
arch medially & decussates at the
level of medulla on the same plane
and reaches to anterior aspect of
medulla.
 Fibers then ascend as a single
bundle, known as medial
lemniscus, through the brain stem.

17.  Third Order Neuron
 Cell body is in VPL nucleus of the
thalamus
 Axons of 3rd order neuron or VPL
pass through posterior limb of
internal capsule & corona radiata to
reach somesthetic area in the
postcentral gyrus of cerebral cortex
(Area 3,1 and 2)
 The contralateral half of
body is represented as
inverted with hand and
mouth situated inferiorly

20. CLINICAL ASPECT OF DOSAL COLUMN

21. LATERAL SPINOTHALAMIC TRACT
 PAIN AND TEMPERATURE
 FIRST ORDER NEURON :
 cell body is in the posterior root ganglion (PRG)
 Axons entering spinal cord from posterior root ganglion
travels for a distance of one or two segments of spinal
cord and form POSTEROLATERAL TRACT OF LISSAUER
 (input from free nerve endings ,thermal receptors)
 Fast conduction delta A type fibers carries sharp pain
 Slow conducting C type fibers carries the sensation of prolonged
burning & aching pain.
 Heat & cold also travel by delta A & C fibers

22.  SECOND ORDER NEURON :
 Cell body is in substantia gelatinosa
in the posterior horn
 Axon crosses the midline within
one spinal segment of the cord
and ascends contralaterally in white
column as lateral spinothalamic
tract.
 In the medulla oblongata it is
accompanied by anterior spinothala
mic tract and now it is known as
SPINAL LEMNISCUS

23.  It continues running in the
posterior part of pons
 In mid brain it lies in tegmentum
lateral to medial lemniscus.
 THIRD ORDER NEURON :
 Cell body is in VPL nucleus of the
thalamus
 Axons ascend through internal
capsule to somatosensory cortex,
post central gyrus (Area 3, 1 and
2)

24. SPINAL LEMINISCUS
 A lemniscus (Greek for ribbon or band) is a bundle of secondary sensory
fibres in the brainstem
 As lateral spinothalamic tract ascends it is accompanied by anterior
spinothalamic tract and spinotectal tract ,these are collectively known as
SPINAL LEMINISCUS

25. ANTERIOR SPINOTHALAMIC PATHWAY
 CRUDE TOUCH AND PRESSURE
 Exactly the same as Lateral spinothalamic pathway except ascends in the anterior
white column
 FIRST ORDER NEURON:
 cell body is in the posterior root ganglion (PRG)
 SECOND ORDER NEURON:
 Cell body is in substantia gelatinosa in the posterior horn
 Axon crosses the midline obliquely in the anterior gray and white
commissure within several segments of spinal cord. and ascends in
contralateral anterior white column as anterior spinothalamic tract .

26.  As the tract ascends in medulla it
accompanies fibers of latera
spinothalamic tract and now known as
SPINAL LEMNISCI.
 It follows the same course reaching
thalamus.
 THIRD ORDER NEURON :
 Cell body is in VPL nucleus of the
thalamus
 Axons ascend through internal
capsule as corona radiata to
somatosensory cortex in post central
gyrus of cerebral cortex

29. MUSCLE JOINT SENSE PATHWAY TO CEREBELLUM
 Anterior spinocerebellar
tract
 Posterior spinocerebellar
tract

30. POSTERIOR SPINOCEREBELLAR PATHWAY
 unconscious proprioception from caudal part of body & legs, like muscle spindles,
tendon organ, joint receptors of trunk and lower limb.
 It is concern with the cordination of limb movement and maintainance of posture.
 Neuron 1:
 Cell body is in PRG
 Axon travels in f. gracilis up to L2
 Neuron 2:
 Cell body is in Clarke’s nucleus
 Axon ascends as posterior spinocerebellar tract in lateral white column, goes
to cerebellum via the inferior cerebellar peduncle
 Does not cross the midline

32. ANTERIOR SPINOCEREBELLAR PATHWAY
 unconscious proprioception caudal part of body & legs. From muscles spindles, tendon
organ joint receptors of upper and lower trunk.
 Neuron 1:
 Cell body is in PRG
 Axon travels in f. gracilis up to L2
 Neuron 2:
 Cell body is in Clarke’s nucleus
 Axon crosses to opposite side then ascends as anterior spinocerebellar tract in contralateral white
column, some fibers runs ipsilaterally in anterior spinocerebellat tract.
 These fibers runs through medddulla and pons and enter cerebellum via the superior cerebellar
peduncle.
 It is said the fibers which crossed at the level of spinal cord they crosses back within the cerebellum

34. OTHER ASCENDING PATHWAYS
Spinoreticular tract:
 Carries dull aching pain from peripheral
type C fibers.
 There are many synapses in reticular
formation of brainstem, but the pathway
then projects to the intralaminar nuclei
of the thalamus.
Spinotectal tract:
 Provides somato-sensory input for
visual reflexes.
Spino-olivary tract:
 Indirect pathway to the cerebellum
Spinovestibular tract:
 Carries information about posture and
body orientation to the vestibular nuclei in
the brainstem.
 It travels with the posterior spinocerebellar
tract.

35. Spino-olivary
Spinoreticular
Spinotectal

36. SPINO TECTAL PATHWAY
 Axons enter spinal cord from posterior root ganglion
 Travel to gray matter where they synapse on 2nd order neurons (un
known)
 Axons of 2nd -order neurons cross median plane & ascend as Spinotectal
tract in anterolateral white column.
 After passing through medulla & pons, they terminate by synapsing with
neurons in superior colliculus of midbrain.
 This pathway provides afferent information for spinovisual reflexes &
brings about movements of eyes & head toward the source of
stimulation

37. SPINO RETICULAR PATHWAY
 Axons enter spinal cord from posterior root ganglion
 Terminate on 2nd order neurons in gray matter.
 Axons of 2nd -order neurons ascend in spinal cord as spinoreticular tract in the
lateral white column.
 Most fibers are uncrossed and terminate by synapsing with neurons of reticular
formation in medulla oblongata, pons and mid brain.
 Spinoreticular tract plays an important role in influencing levels of
consciousness.

39. SPINO-OLIVARY PATHWAY
 Axons enter spinal cord from posterior root ganglion
 Terminate on 2nd -order neurons in posterior gray column.
 Axons from the 2nd order neurons cross midline & ascend as spino-olivary
tract in the white matter
 Axons end by synapsing on 3rd -order neurons in inferior olivary nuclei in
medulla oblongata.
 Axons of 3rd -order neurons cross midline & enter cerebellum through inferior
cerebellar peduncle.
 Spino-olivary tract conveys information to cerebellum from cutaneous and
proprioceptive organs.