spinal cord tracts by dr prc

1. Nervous system
 Functional point of view it consist ofFunctional point of view it consist of
1.1. Sensory partSensory part
2.2. Motor partMotor part
3.3. Higher functionHigher function

2.  There is a continuous flow of information between theThere is a continuous flow of information between the
brain, spinal cord, and peripheral nerves.brain, spinal cord, and peripheral nerves. ThisThis
information is relayed by sensory (ascending) andinformation is relayed by sensory (ascending) and
motor (descending) ‘pathways’.motor (descending) ‘pathways’.
 Generally the pathways:Generally the pathways:
 Consists of a chain ofConsists of a chain of tracts,tracts, associatedassociated nucleinuclei andand
varying number of relays (varying number of relays (synapsessynapses))
 Consist of two or three neuronsConsist of two or three neurons
 Involve both the brain and spinal cordInvolve both the brain and spinal cord

3. CENTRAL NERVOUS SYSTEM
integration / processing / modulating
stimulus
receptor neurone
motor / descending tracts
effector organ / response
PNS
transmission
lower motor neurone
sensory / ascending tracts

4. SOMATO SENSORY
PHYSIOLOGY

5. It consist of mainlyIt consist of mainly
1.1.ReceptorsReceptors
2.2.Various ascending tractVarious ascending tract
3.3.Somatosensory cortexSomatosensory cortex

6. Sensory PathwaysSensory Pathways

7. Sensory Pathways
 Monitor conditions both inside the body and in theMonitor conditions both inside the body and in the
external environmentexternal environment
 Sensation-stimulated receptor passes informationSensation-stimulated receptor passes information
to the CNS via afferent (sensory) fibersto the CNS via afferent (sensory) fibers
 Most sensory information is processed in the spinalMost sensory information is processed in the spinal
cord , thalamus, or brain stem. Only 1% reachescord , thalamus, or brain stem. Only 1% reaches
the cerebral cortex and our conscious awarenessthe cerebral cortex and our conscious awareness
 Processing in the spinal cord can produce a rapidProcessing in the spinal cord can produce a rapid
motor response (stretch reflex)motor response (stretch reflex)
 Processing within the brain stem may result inProcessing within the brain stem may result in
complex motor activities (positional changes in thecomplex motor activities (positional changes in the
eye, head, trunk)eye, head, trunk)

8. Sensory Pathways
 Contain a sequence ofContain a sequence of THREETHREE
neuronsneurons from the receptor to thefrom the receptor to the
cerebral cortexcerebral cortex
 First order neuron:First order neuron: SensorySensory
neuron that delivers informationneuron that delivers information
from the receptor to the CNS.from the receptor to the CNS.
 Cell body located in the dorsalCell body located in the dorsal
root ganglion. The Axon (centralroot ganglion. The Axon (central
process)process) passes to the spinalpasses to the spinal
cord through the dorsal root ofcord through the dorsal root of
spinal nervespinal nerve gives manygives many
collaterals which take part incollaterals which take part in
spinal cord reflexesspinal cord reflexes runsruns
ipsilaterallyipsilaterally and synapses withand synapses with
second-order neurons in thesecond-order neurons in the
cord and medulla oblongatacord and medulla oblongata
11
22
33

9. dorsal root
dorsal root
ganglion spinal
nerve
dorsal
horn
FIRST ORDER NEURON

10.  Second orderSecond order
neuron:neuron:
 Has cell body in the spinalHas cell body in the spinal
cord or medulla oblongatacord or medulla oblongata
 AxonAxon crosses the midlinecrosses the midline
decussatedecussate &&
 Terminate on 3rd orderTerminate on 3rd order
neuronneuron in VPL nucleus ofin VPL nucleus of
thalamusthalamus

11. SECOND ORDER NEURON
• cross the mid line
• in front of central canal
VPL
1st
2nd

12.  Third order neuron:Third order neuron:
 Has cell body inHas cell body in
thalamusthalamus
 Axon terminates onAxon terminates on
cerebral cortexcerebral cortex
ipsilaterallyipsilaterally

13. Ascending Spinal Tracts
Transmit impulses:
 Concerned with specific sensory modalities: pain,
temperature, touch, proprioception, that reach a
conscious level (cerebral cortex)
 Dorsal column or Lemniscal system
 Antero-lateral Spinothalmic tracts
- ASTT
- LSTT
 From tactile and stretch receptors to subconscious
centers (cerebellum)
 Spino-cerebellar tracts
- Dorsal Spino-cerebellar tracts
- Ventral Spino-cerebellar tracts

15.  Three major pathways carry sensory informationThree major pathways carry sensory information
 Posterior column pathway (gracile & cuneatePosterior column pathway (gracile & cuneate
fasciculi)fasciculi)
 Anterolateral pathway (spinothalamic)Anterolateral pathway (spinothalamic)
 Spinocerebellar pathwaySpinocerebellar pathway

16. Dorsal ColumnDorsal Column or Lemniscal system.
 Contains two tracts,Contains two tracts, FasciculusFasciculus
gracilis (FG)gracilis (FG) && fasciculusfasciculus
cuneatus (FC)cuneatus (FC)
 It carries sensations of fine touch,It carries sensations of fine touch,
position, viberation, two pointposition, viberation, two point
discrimination & stereognosis.discrimination & stereognosis.
 Contain the axons ofContain the axons of primaryprimary
afferent neuronsafferent neurons that havethat have
entered cord through dorsalentered cord through dorsal
roots of spinal nervesroots of spinal nerves
FG contains fibers received at sacral, lumbar and lower
thoracic levels, FC contains fibers received at upper
thoracic and cervical levels

17. 17

18. 18

19.  Fibers ascend withoutFibers ascend without
interruption where theyinterruption where they
terminate uponterminate upon 22ndnd
orderorder
neuronsneurons inin nucleus gracilis andnucleus gracilis and
nucleus cuneatusnucleus cuneatus
 The axons of the 2The axons of the 2ndnd
orderorder
neuronsneurons decussatedecussate in thein the
medulla asmedulla as internal arcuateinternal arcuate
fibersfibers and ascend through theand ascend through the
brain stem asbrain stem as medialmedial
lemniscuslemniscus..
 The medial lemniscusThe medial lemniscus
terminates in theterminates in the ventralventral
posterior nucleus of theposterior nucleus of the
thalamusthalamus uponupon 33rdrd
orderorder
neuronsneurons, which project to the, which project to the
somatosensory cortexsomatosensory cortex
(thalamocortical fibers)(thalamocortical fibers)

22. Spinothalamic TractsSpinothalamic Tracts
 Located lateral and AnteriorLocated lateral and Anterior
horn of spinal cordhorn of spinal cord
 Anterior spinothalamic tractAnterior spinothalamic tract
carries crude touch andcarries crude touch and
pressure,pressure,
 Lateral spinothalamic tractLateral spinothalamic tract
carries pain and temperature.carries pain and temperature.
 In brain stem, constitute theIn brain stem, constitute the
spinal lemniscusspinal lemniscus
 Fibers are highly somato-Fibers are highly somato-
topically arranged, with thosetopically arranged, with those
for thefor the lower limblower limb lying mostlying most
superficially and those forsuperficially and those for
the upper limb lying deeplythe upper limb lying deeply Information is sent to the
primary sensory cortex on
the opposite side of the body

23. Lateral Spinothalamic TractLateral Spinothalamic Tract
 Carries impulses concernedCarries impulses concerned
withwith painpain andand thermalthermal
sensations.sensations.
 Axons of 1Axons of 1stst
order neuronsorder neurons
terminate in the dorsal hornterminate in the dorsal horn
 Axons of 2Axons of 2ndnd
order neuronorder neuron
(mostly in the(mostly in the nucleusnucleus
proprius), decussate withinproprius), decussate within
one segmentone segment of their origin,of their origin,
by passing through the ventralby passing through the ventral
white commissure & terminatewhite commissure & terminate
on 3on 3rdrd
order neurons in ventralorder neurons in ventral
posterior nucleus of theposterior nucleus of the
thalamusthalamus
 Thalamic neurons project toThalamic neurons project to
thethe somatosensory cortexsomatosensory cortex

24. 24

25. Anterior Spinothalamic TractAnterior Spinothalamic Tract
 Carries impulses concernedCarries impulses concerned
withwith non- discriminative touchnon- discriminative touch
andand pressurepressure
 Axons of 1Axons of 1stst
order neuronsorder neurons
enter cord terminate in theenter cord terminate in the
dorsal horndorsal horn
 Axons of 2Axons of 2ndnd
order neuronorder neuron
(mostly in the(mostly in the nucleusnucleus
proprius) may ascend severalproprius) may ascend several
segments before crossingsegments before crossing toto
opposite side by passingopposite side by passing
through the ventral whitethrough the ventral white
commissure & terminate on 3commissure & terminate on 3rdrd
order neurons inorder neurons in ventralventral
posterior nucleusposterior nucleus of theof the
thalamusthalamus
 Thalamic neurons project toThalamic neurons project to
thethe somatosensory cortexsomatosensory cortex

26. 26
DORSAL COLUMNDORSAL COLUMN
PATHWAYPATHWAY
 CARRIES FINE TOUCH,CARRIES FINE TOUCH,
POSITION, PRESSURE,POSITION, PRESSURE,
VIBRATION, TWO POINTVIBRATION, TWO POINT
DESRIMINATIONDESRIMINATION
stereognosisstereognosis
 AFFERENT SENSORYAFFERENT SENSORY
FIBERS AFIBERS Aββ TYPE.TYPE.
 VERY FAST VELOCITYVERY FAST VELOCITY
30 – 70 m/s30 – 70 m/s
 3 NEURON SYSTEM3 NEURON SYSTEM
(SEE THE DIAGRAM)(SEE THE DIAGRAM)
ANTEROLATERAL PATHWAYANTEROLATERAL PATHWAY
 CARRIES PAIN &CARRIES PAIN &
TEMPRATURE (lat. Sp.Th)TEMPRATURE (lat. Sp.Th)
 CRUDE TOUCH & PRESSURECRUDE TOUCH & PRESSURE
( VENT, Sp. Th)( VENT, Sp. Th)
 AFFERENT SENSORY FIBERSAFFERENT SENSORY FIBERS
AAδδ (MYELINATED) FAST PAIN(MYELINATED) FAST PAIN
 C FIBERS( UNMYELINATED)C FIBERS( UNMYELINATED)
SLOW PAINSLOW PAIN
 RELATIVELY SLOWRELATIVELY SLOW
VELOCITY AVELOCITY Aδδ – 6 – 30 m/s. C– 6 – 30 m/s. C
– 0.5 – 2 m/s.– 0.5 – 2 m/s.
 3 NEURON SYSTEM3 NEURON SYSTEM
(SEE THE DIAGRAM)(SEE THE DIAGRAM)

27. Spino-cerebellar TractsSpino-cerebellar Tracts
 The spinocerebellar systemThe spinocerebellar system
consists of a sequence ofconsists of a sequence of
onlyonly two neuronstwo neurons
 Two tracts:Two tracts: Posterior / dorsalPosterior / dorsal
&& Anterior/ VentralAnterior/ Ventral
 Located near theLocated near the
dorsolateral anddorsolateral and
ventrolateral surfaces of theventrolateral surfaces of the
cordcord
 Contain axons of theContain axons of the secondsecond
order neuronsorder neurons
 It Carry information(nonIt Carry information(non
conscious) arising from theconscious) arising from the
muscle spindles, Golgimuscle spindles, Golgi
tendon organs and tectiletendon organs and tectile
receptors to the cerebellumreceptors to the cerebellum
for the control of posture andfor the control of posture and
coordination of movementscoordination of movements

28. Posterior SpinocerebellarPosterior Spinocerebellar
TractsTracts
 Present only above level L3Present only above level L3
 11stst
order neuron enter spinalorder neuron enter spinal
cord via DRGcord via DRG
 The cell bodies of 2The cell bodies of 2ndnd
orderorder
neuron lie inneuron lie in Clark’sClark’s
column(nucleus dorsalis)column(nucleus dorsalis)
 Axons of 2Axons of 2ndnd
order neuronorder neuron
terminateterminate ipsilaterallyipsilaterally
(uncrossed) in the(uncrossed) in the cerebellarcerebellar
cortexcortex by entering throughby entering through
thethe inferior cerebellarinferior cerebellar
pedunclepeduncle

29. Ventral SpinocerebellarVentral Spinocerebellar
TractsTracts 11stst
order neuron enter spinal cordorder neuron enter spinal cord
via DRG and relay in dorsal horn.via DRG and relay in dorsal horn.
 The cell bodies of 2The cell bodies of 2ndnd
order neuronorder neuron
lie inlie in base of the dorsal hornbase of the dorsal horn of theof the
lumbosacral segmentslumbosacral segments
 Axons of 2Axons of 2ndnd
order neuronorder neuron crosscross toto
opposite side, ascend as far asopposite side, ascend as far as
the midbrain, and then make athe midbrain, and then make a
sharp turn caudally and enter thesharp turn caudally and enter the
superior cerebellar pedunclesuperior cerebellar peduncle
 The fibers cross the midline for aThe fibers cross the midline for a
second time within the cerebellumsecond time within the cerebellum
before terminating in thebefore terminating in the
cerebellar cortexcerebellar cortex
 Both spinocerebellar tracts conveyBoth spinocerebellar tracts convey
sensory information to the samesensory information to the same
side of the cerebellumside of the cerebellum

31. sensation receptors pathways destination
Pain and temperature Free nerve
endings
Lateral STT
Spinal lemniscus
Postcentra
l gyrus
Light touch and
pressure
Free nerve
endings
Anterior STT
Spinal lemniscus
Postcentra
l gyrus
Discriminative touch,
vibratory sense,
conscious
muscle joint sense
Meissner’s
corpuscle,
pacinian
corpuscles,
muscle spindles,
tendon
organs
Fasciculus gracilis and
cuneatus
Medial lemniscus
Postcentra
l gyrus
Main somatosensory pathways

32. Sensory Homonculus

33.  Sensory cortex / postSensory cortex / post
central gyrus / S-I orcentral gyrus / S-I or
A=3,1,2A=3,1,2
 Homonculus = map ofHomonculus = map of
the manthe man
 Sensory homonculusSensory homonculus
= map of the sensory= map of the sensory
area in manarea in man

34.  Different area of the bodyDifferent area of the body
have a Tropographicalhave a Tropographical
representation in the postrepresentation in the post
central gyrus.central gyrus.
 Body appears upside-Body appears upside-
down in PCGdown in PCG
 Foot area occupies in mostFoot area occupies in most
medial part of cortexmedial part of cortex
 Face area located in lateralFace area located in lateral
part of cortexpart of cortex
 Tongue occupies furtherTongue occupies further
down than facedown than face

35.  Area of body occupy a muchArea of body occupy a much
bigger space irrespective ofbigger space irrespective of
the actual size of the organthe actual size of the organ
 Index finger ,face &lowerIndex finger ,face &lower
lips occupy large area wherelips occupy large area where
as actual size of the smallas actual size of the small
organ.organ.
 Area of thigh & trunk (bigArea of thigh & trunk (big
organ) for smallorgan) for small
 It represent the opposite halfIt represent the opposite half
of the body for DC/ALSTTof the body for DC/ALSTT
becoz crossedbecoz crossed the midlinethe midline

36. 36
Different Sensations
TOUCH
 Touch receptors are more numerous in the skin of fingers, lipsTouch receptors are more numerous in the skin of fingers, lips
& less in the skin of trunk.& less in the skin of trunk.
 Many receptors are around hair follicles, subcutaneous tissuesMany receptors are around hair follicles, subcutaneous tissues
& hairless areas.& hairless areas.
 Touch receptors transmits impulses via ATouch receptors transmits impulses via Aββ sensory fibers tosensory fibers to
CNS.CNS.
 Their diameter is 5 – 12Their diameter is 5 – 12 μμm, conduction velocity is 30 – 70m, conduction velocity is 30 – 70
m/sec.m/sec.
 Some touch goes via C fibers.Some touch goes via C fibers.
 Touch information is transmitted by Dorsal column (fine), andTouch information is transmitted by Dorsal column (fine), and
ventral spinothalamic tract (crude)ventral spinothalamic tract (crude)

37. 37
 It is awareness of position of body in space. Information isIt is awareness of position of body in space. Information is
carried by dorsal column, input goes to cerebellum & sensorycarried by dorsal column, input goes to cerebellum & sensory
cortex.cortex.
 Disease of dorsal column produces Ataxia( due to interruptionDisease of dorsal column produces Ataxia( due to interruption
of proprioception input to cerebellum).of proprioception input to cerebellum).
 Sense organ for proprioception – spray endings, pacinianSense organ for proprioception – spray endings, pacinian
corpuscle in synovia & ligaments, touch receptors in skin &corpuscle in synovia & ligaments, touch receptors in skin &
other tissues, muscle spindle – these sensation are synthesizeother tissues, muscle spindle – these sensation are synthesize
in the cortex into conscious picture of position of body inin the cortex into conscious picture of position of body in
space.space.
Different Sensations
PROPRIOCEPTION

38. 38
 When vibrating tuning fork is applied to bony partWhen vibrating tuning fork is applied to bony part
we feel thrill.we feel thrill.
 Receptor – pacinian corpuscleReceptor – pacinian corpuscle
 Sensation is carried by dorsal column.Sensation is carried by dorsal column.
 Vibration sensation decreases in diabetesVibration sensation decreases in diabetes
mellitus, pernicious anemia due to degenerationmellitus, pernicious anemia due to degeneration
of dorsal columnof dorsal column..
Different Sensations
VIBRATORY SENSE

39. 39
 The minimal distance by which two touch stimuli must beThe minimal distance by which two touch stimuli must be
separated to be perceived as separate is called two pointseparated to be perceived as separate is called two point
threshold.threshold.
 It depends on touch receptors and cortical component.It depends on touch receptors and cortical component.
 Its magnitude varies from place to place on body.Its magnitude varies from place to place on body.
 Distance is smaller when touch receptors are most abundant e.g.Distance is smaller when touch receptors are most abundant e.g.
fingers where two stimuli can be felt if they are separated byfingers where two stimuli can be felt if they are separated by
3mm.3mm.
 But at the back points must be separated by 65mm or moreBut at the back points must be separated by 65mm or more
before they can be identified as separate.before they can be identified as separate.
Different Sensations
TWO POINT DISCRIMINATION

40. 40
 The ability to identify objects by hand withoutThe ability to identify objects by hand without
looking at them is called as stereognosis.looking at them is called as stereognosis.
 Normal person can identify objects like coin, key.Normal person can identify objects like coin, key.
 It depends on touch & pressure sensation, dorsalIt depends on touch & pressure sensation, dorsal
column & sensory cortex.column & sensory cortex.
 Impaired stereognosis is an early sign of damage toImpaired stereognosis is an early sign of damage to
the cerebral cortex. (parietal lobe lesion)the cerebral cortex. (parietal lobe lesion)
Different Sensations
STEREOGNOSIS

41. 41
 Skin has cold sensitive area & heat sensitive area.Skin has cold sensitive area & heat sensitive area.
Receptors are free nerve endings.Receptors are free nerve endings.
 Cold receptors are 4 – 10 times more than warmCold receptors are 4 – 10 times more than warm
sensitive spots.sensitive spots.
 Cold receptor responds from 10 – 38Cold receptor responds from 10 – 38 oo
C.C.
 Warm receptor responds from 30– 45Warm receptor responds from 30– 45 oo
C.C.
 Afferent from cold receptors – AAfferent from cold receptors – Aδδ & C fibers.& C fibers.
 Afferent from warm receptors – C fibers.Afferent from warm receptors – C fibers.
 Temperature sensation is carried via lateralTemperature sensation is carried via lateral
spinothalamic tract.spinothalamic tract.
Different Sensations
TEMPERATURE

42. 42
THERMORECPTOR
NOCICEPTORS

43. 43
 Pain receptors or nociceptors – free nerve endings.Pain receptors or nociceptors – free nerve endings.
 Pain sensation are carried by two types of nerve fibers.Pain sensation are carried by two types of nerve fibers.
 AAδδ (myelinated) -2 – 5(myelinated) -2 – 5 μμm.in diameter, conduction velocity – 12m.in diameter, conduction velocity – 12
– 30 m/sec.– 30 m/sec.
 For fast pain (sharp localized)For fast pain (sharp localized)
 C fibers (unmyelinated) 0.4 – 1.2C fibers (unmyelinated) 0.4 – 1.2μμm. in diameter, conductionm. in diameter, conduction
velocity – 0.5 – 2 m/sec.velocity – 0.5 – 2 m/sec.
 For slow pain (dull, diffuse)For slow pain (dull, diffuse)
 Both ABoth Aδδ & C fibers terminate in dorsal horn.& C fibers terminate in dorsal horn.
Pain is carried via lateral spinothalamic tract.Pain is carried via lateral spinothalamic tract.
Different Sensations
PAIN

44. Somatic Motor PathwaysSomatic Motor Pathways

45. Motor PathwaysMotor Pathways
 CNS issues motor commands in response toCNS issues motor commands in response to
information provided by sensory systems, sent byinformation provided by sensory systems, sent by
the somatic nervous system (SNS) and thethe somatic nervous system (SNS) and the
autonomic nervous system (ANS)autonomic nervous system (ANS)
 Conscious and subconscious motor commandsConscious and subconscious motor commands
control skeletal muscles by traveling over 3control skeletal muscles by traveling over 3
integrated motor pathwaysintegrated motor pathways
 TheThe corticospinalcorticospinal pathwaypathway – voluntary control of– voluntary control of
motor activitymotor activity
 Corticobulbar tractsCorticobulbar tracts
 Corticospinal tractsCorticospinal tracts
 TheThe medialmedial andand laterallateral pathwayspathways – modify or direct– modify or direct
skeletal muscle contractions by stimulating,skeletal muscle contractions by stimulating,
facilitating, or inhibiting lower motor neuronsfacilitating, or inhibiting lower motor neurons

46. Motor PathwaysMotor Pathways
• Contain a sequence ofContain a sequence of TWOTWO
neuronsneurons from the cerebralfrom the cerebral
cortex or brain stem to thecortex or brain stem to the
musclesmuscles
• Upper motor neuronUpper motor neuron : has cell: has cell
body in the cerebral cortex orbody in the cerebral cortex or
brain stem, axonbrain stem, axon decussatesdecussates
before terminating on thebefore terminating on the
lower motor neuronlower motor neuron
• Lower motor neuronLower motor neuron: has cell: has cell
body in the ventral horn of thebody in the ventral horn of the
spinal cord, axon runs in thespinal cord, axon runs in the
ipsilateralipsilateral ventral root of theventral root of the
spinal nerve and supply thespinal nerve and supply the
muscle.muscle.
UMN
LMN

47. Descending Spinal Tracts
 OriginateOriginate from thefrom the cerebral cortexcerebral cortex && brainbrain
stemstem
 ConcernedConcerned with:with:
 Control of movementsControl of movements
 Muscle toneMuscle tone
 Spinal reflexes & equilibriumSpinal reflexes & equilibrium
 Modulation of sensory transmission toModulation of sensory transmission to
higher centershigher centers
 Spinal autonomic functionsSpinal autonomic functions

48.  The motor pathways areThe motor pathways are
divided into two groupsdivided into two groups
 Direct pathwaysDirect pathways
(voluntary motion(voluntary motion
pathways) -pathways) - thethe
pyramidal tractspyramidal tracts
 Indirect pathwaysIndirect pathways
(postural pathways)(postural pathways),,
essentially all others -essentially all others -
the extrapyramidalthe extrapyramidal
pathwayspathways

49. Direct (Pyramidal) SystemDirect (Pyramidal) System
 Regulates fast and fine (skilled) movementsRegulates fast and fine (skilled) movements
 Originate in the pyramidal neurons in theOriginate in the pyramidal neurons in the
precentral gyri,precentral gyri,
 Impulses are sent through theImpulses are sent through the corticospinalcorticospinal
tractstracts and synapse in the anterior hornand synapse in the anterior horn
 Stimulation of anterior horn neurons activatesStimulation of anterior horn neurons activates
skeletal musclesskeletal muscles
 Part of the direct pathway, calledPart of the direct pathway, called corticobulbarcorticobulbar
tractstracts, innervates cranial nerve nuclei, innervates cranial nerve nuclei

50. Indirect (Extrapyramidal)Indirect (Extrapyramidal)
SystemSystem
 Complex and multisynaptic pathwaysComplex and multisynaptic pathways
 The system includes:The system includes:
• Rubrospinal tractsRubrospinal tracts: control flexor muscles: control flexor muscles
• Vestibulospinal tractsVestibulospinal tracts: maintain balance and: maintain balance and
postureposture
• Tectospinal tractsTectospinal tracts: mediate head neck, and eye: mediate head neck, and eye
movementmovement
• Reticulospinal tractsReticulospinal tracts

51. Descending Spinal TractsDescending Spinal Tracts
 PyramidalPyramidal
 CorticospinalCorticospinal
 ExtrapyramidalExtrapyramidal
 RubrospinalRubrospinal
 TectospinalTectospinal
 VestibulospinalVestibulospinal
 OlivospinalOlivospinal
 ReticulospinalReticulospinal
 DescendingDescending
Autonomic FibersAutonomic Fibers

52. Corticospinal Tracts
 ConcernedConcerned withwith
voluntary, discrete, skilledvoluntary, discrete, skilled
movements, especiallymovements, especially
those of distal parts ofthose of distal parts of
the limbs (fractionatedthe limbs (fractionated
movements)movements)
 InnervateInnervate thethe
contralateral side of thecontralateral side of the
spinal cordspinal cord
 ProvideProvide rapid directrapid direct
method for controllingmethod for controlling
skeletal muscleskeletal muscle

53.  OriginOrigin: motor and sensory: motor and sensory
corticescortices
 Axons pass throughAxons pass through coronacorona
radiataradiata,, internal capsuleinternal capsule,, cruscrus
cerebricerebri andand pyramidpyramid ofof
medulla oblongatamedulla oblongata
 In the caudal medulla aboutIn the caudal medulla about
75-90%75-90% of the fibersof the fibers
decussatedecussate and form theand form the
lateral corticospinal tractlateral corticospinal tract
 Rest of the fibers remainRest of the fibers remain
ipsilateralipsilateral and formand form anterioranterior
corticospinal tractcorticospinal tract. They. They
also decussate beforealso decussate before
terminationtermination

54.  DistributionDistribution::
 55% terminate at55% terminate at
cervicalcervical regionregion
 20% at20% at thoracicthoracic
 25% at25% at lumbosacrallumbosacral
levellevel
 TerminationTermination:: Ventral hornVentral horn
neuronsneurons (mostly through(mostly through
interneurons, a few fibersinterneurons, a few fibers
terminate directly)terminate directly)
 Corticobulbar tracts endend
at the motor nuclei of CNsat the motor nuclei of CNs
of the contralateral sideof the contralateral side

55. Rubrospinal TractRubrospinal Tract
 ControlsControls the tone of limbthe tone of limb
flexor muscles, beingflexor muscles, being
excitatory to motor neuronsexcitatory to motor neurons
of these musclesof these muscles
 OriginOrigin: Red nucleus: Red nucleus
 Axons course ventro-Axons course ventro-
medially, cross inmedially, cross in ventralventral
tegmental decussationtegmental decussation,,
descend in spinal corddescend in spinal cord
ventral to the lateralventral to the lateral
corticospinal tractcorticospinal tract
 Cortico-rubro-spinal pathwayCortico-rubro-spinal pathway
(Extrapyramidal)(Extrapyramidal)

56. Tectospinal Tract
 Mediates reflex movements ofMediates reflex movements of
the head and neck in responsethe head and neck in response
to visual stimulito visual stimuli
 OriginOrigin: Superior colliculus: Superior colliculus
 Axons course ventro-mediallyAxons course ventro-medially
around the periaqueductal grayaround the periaqueductal gray
matter, cross inmatter, cross in dorsaldorsal
tegmental decussationtegmental decussation,,
descend in spinal cord near thedescend in spinal cord near the
ventral median fissure,ventral median fissure,
terminate mainly interminate mainly in cervicalcervical
segmentssegments
 Cortico-tecto-spinal pathwayCortico-tecto-spinal pathway
(Extrapyramidal)(Extrapyramidal)

57. Vestibulospinal Tracts
 Lateral VestibulospinalLateral Vestibulospinal
TractsTracts
 OriginOrigin:: lateral vestibularlateral vestibular
(Deiter’s) nucleus(Deiter’s) nucleus
 Axons descendAxons descend ipsilaterallyipsilaterally inin
the ventral funiculusthe ventral funiculus
 Terminate on ventral hornTerminate on ventral horn
cells throughout the length ofcells throughout the length of
spinal cordspinal cord
 Has excitatory influencesHas excitatory influences
upon extensor motor neurons,upon extensor motor neurons,
control extensor muscle tonecontrol extensor muscle tone
in the antigravity maintenancein the antigravity maintenance
of postureof posture

58. Vestibulospinal Tracts
 Medial vestibulospinalMedial vestibulospinal
tracttract
 OriginOrigin:: medial vestibularmedial vestibular
nucleusnucleus
 Axons descendAxons descend bilaterallybilaterally inin
the ventral funiculus, with thethe ventral funiculus, with the
medial longitudinal fasciculusmedial longitudinal fasciculus
 Most of the fibers end in theMost of the fibers end in the
cervical region, some reachingcervical region, some reaching
upper thoracic segmentsupper thoracic segments
 Involved in movements of theInvolved in movements of the
head required for maintaininghead required for maintaining
equilibriumequilibrium

59. Reticulospinal Tracts
 InfluenceInfluence voluntary movement,voluntary movement,
reflex activity and muscle tone byreflex activity and muscle tone by
controlling the activity of bothcontrolling the activity of both
alpha and gamma motor neuronsalpha and gamma motor neurons
 Mediate pressor and depressorMediate pressor and depressor
effect on the circulatory systemeffect on the circulatory system
 Are involved in control of breathingAre involved in control of breathing
 OriginOrigin: pontine & medullary: pontine & medullary
reticular formationreticular formation
 Medial (pontine) reticulospinalMedial (pontine) reticulospinal
tract descendstract descends ipsilaterallyipsilaterally
 Lateral (medullary) reticulospinalLateral (medullary) reticulospinal
tract descendstract descends bilaterallybilaterally
 Both tracts located in the ventralBoth tracts located in the ventral
funiculusfuniculus

60. Descending Autonomic Fibers
 The higher centersThe higher centers
associated with the control ofassociated with the control of
autonomic activity areautonomic activity are
situated mainly in thesituated mainly in the
hypothalmaushypothalmaus
 The fibers run in theThe fibers run in the
reticulospinal tractsreticulospinal tracts
 Terminate on theTerminate on the autonomicautonomic
neuronsneurons in the lateral horn ofin the lateral horn of
thoracic & upper lumbarthoracic & upper lumbar
(sympathetic) and sacral(sympathetic) and sacral
segments (parasympathetic)segments (parasympathetic)
levels of the spinal cordlevels of the spinal cord

61. UMNPUMNP
 Lost ( skilled activities)Lost ( skilled activities)
 Increased.(spastic typeIncreased.(spastic type
paralysis, clasp knifeparalysis, clasp knife
rigidity)rigidity)
 LostLost
 Babinski’s sign +iveBabinski’s sign +ive
 ExaggeratedExaggerated
 PresentPresent
 NilNil
LMNPLMNP
 LostLost
 Lost , FlaccidityLost , Flaccidity
(flaccid type of(flaccid type of
paralysis)paralysis)
 Lost when particular neuronLost when particular neuron
supplying the muscle issupplying the muscle is
damageddamaged
 Normal flexor planterNormal flexor planter
response.response.
 LostLost
 AbsentAbsent
 Marked wastingMarked wasting
Sign & symp
1.Voluntary
muscle power
2.Tone of the
Muscle
3.Superficial
reflex
4.Planter reflex
5.Tendon Jerk
6.Clonus
7.Muscleatrophy

62. LoveLove
naturenature