MOTOR SYSTEM MOTOR TRACTS

DESCENDING TRACTS

1. DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
MOTOR
SYSTEM

2. OBJECTIVES
Introduction.
Components of Somatic motor control
system.
Skeletal Muscle : The Effector organ of
somatic motor system.
Reflex activity.
Regulation of posture.
Vestibular apparatus & equilibrium.
Monday, May 16, 2016

3. INTRODUCTION.
Effector organ- Skeletal
muscle.
Muscle activity decided by –
Rate & Pattern of discharge
in Motor neuron.
Motor unit – Single Motor
Neuron & muscle fibre that it
innervates.
Motor Neuronal Pool – All
Motor Neuron for a given
muscle.
Monday, May 16, 2016

4. INTRODUCTION.
Lower Motor Neuron
& Final Common
Pathway – Alpha
motor neuron &
Motor nuclei of
cranial nerves.
Monday, May 16, 2016

5. SOMATIC MOTOR ACTIVITY.
Voluntary Movements –
learns by doing & performance
improves with repetition.
(Synaptic Plasticity)
Reflex Responses.
Rhythmic Motor Activities –
Initiated & terminated
voluntarily.
Control Of Posture &
Equilibrium –Goal & direction
oriented phasic movements.
Monday, May 16, 2016

6. MEDIAL VS LATERAL MOTOR
SYSTEM.
Medial Motor
System.
Anterior Cortico-spinal
tract.
Corticobulbar tract.
Lateral & Medial
Vestibulospinal tract.
Reticulospinal tract.
Lateral Motor
System.
Lateral corticospinal
tract.
Rubro spinal tract.
Corticobulbar tract.
Monday, May 16, 2016

7. CONTROL OF SOMATIC MOTOR
ACTIVITY.
3 Tier System to
control.
Highest level – Cerebral
Cortex for generation of
ideas & giving motor
commands.
Middle level – for
Supervising.
Lower level – for
Execution.
Monday, May 16, 2016

8. ROLE OF SENSORY RECEPTORS IN
MOTOR CONTROL ACTIVITY.
Proprioceptors in skin,
Muscle & joints gives
feedback
&
 Adjust Motor
commands.
Monday, May 16, 2016

9. OVERVIEW TO STUDY MOTOR
CONTROL SYSTEM.
Components of
somatic motor control
system.
Skeletal muscles: the
effector organ.
Reflexes.
Regulation of
posture &
equilibrium.
Monday, May 16, 2016

10. COMPONENTS OF SOMATIC
MOTOR CONTROL SYSTEM.
Highest level of motor control.
Middle level of motor control.
Lowest level of motor control.
Monday, May 16, 2016

11. HIGHEST LEVEL OF MOTOR
CONTROL.
Cerebral cortex.
Motor cortex.
Descending motor
pathways from motor
cortex.
Monday, May 16, 2016

12. CEREBRAL CORTEX
MOTOR CORTEX.
Areas of motor cortex.
Primary motor cortex
(4) – Frontal lobe within
pre-central gyrus.
Premotor cortex
6,8,44,45
Supplementary motor
cortex – Medial surface
behind Primary Motor
Area.
Monday, May 16, 2016

13. FUNCTIONAL ROLE OF MOTOR
CORTEX.
Primary motor cortex 4 –
execution of movements
Premotor cortex-
6 – Proximal & axial movements &
skill
8 – Coordination of eye movements.
44,45 – Coordination of muscle of
speech.
Head rotation,
Supplementary motor cortex –
Responsible for generating idea
for Movement. (With Cerebellum
& BG)
Monday, May 16, 2016

14. PLASTICITY
PROPERTY OF MOTOR CORTEX
Motor cortex learns by
doing.
Performance improves
with Repetition.
Confirmed by PET scan
& fMRI.
Finger area enlargement
in Musician.
Monday, May 16, 2016

15. TOPOGRAPHICAL REPRESENTATION
OF MOTOR AREAS IN CORTEX
Monday, May 16, 2016
MOTOR HOMONCULUS

16. DESCENDING MOTOR PATHWAYS
FROM MOTOR CORTEX.
Pyramidal tracts
Extra-pyramidal
tracts
Monday, May 16, 2016

17. CRITERIA TO DESCRIBE
TRACTS
Synonyms
Origin
Course
Crossing
Termination.
Function.
Applied physiology.
Monday, May 16, 2016

18. PYRAMIDAL TRACTS
Corticospinal tracts –
axons from cortex to
spinal cord.
Origin –
 Primary Motor
Cortex(4) – 30%
Premotor Area – 30%
Somato-sensory Area –
40%
Monday, May 16, 2016

19. COURSE & TERMINATION.
From cortex descend as a
part of Corona Radiata –
post limb if Internal
Capsule – brain stem
forms Pyramid in
Medulla.
Then cross & forms 2
tracts
Lateral corticospinal T.
Anterior T.
Monday, May 16, 2016

20. LATERAL CORTICOSPINAL
TRACT
80% of fibers crossed to
opp side.
Fibres descend terminate
on internuncial
neurons/ventral horn
cells – forms UMN
From ventral horn cells
to skeletal muscle – LMN.
Monday, May 16, 2016

21. ANTERIOR
CORTICOSPINALTRACT.
20% of uncrossed pyramidal
fibres.
Descend in Ant white
funiculus only up to MID-
THORACIC Region.
Then in spinal cord crosses
to opposite side & terminate
on ventral horn cells.
Thus Cortex on one side
connect to ventral horn cells
on opposite side.
Monday, May 16, 2016

22. SALIENT FEATURES.
Fibres are Unmyelinated at
birth.
Myelination begins in 2
nd

postnatal week &
completed by 2 years.
80% - Small & 20% Large
diameter.
Large fibres disappears at old
age causes Automatic
shaking movements.
Monday, May 16, 2016

23. FUNCTIONS.
Control voluntary fine
skilled Movements.
Closely packed in
Internal capsule & brain
stem so small lesion
causes wide Paralysis.
Send collateral to Basal
ganglia, cerebellum. for
coordination
Monday, May 16, 2016

24. EXTRA-PYRAMIDAL TRACTS
Remaining tracts other
than pyramidal.
Rubro-spinal tract.
Vestibulospinal tract.
Reticulospinal tract.
Tecto-spinal tract.
Olivo-spinal tract.
Medial longitudinal
fasciculus.
Monday, May 16, 2016

25. RUBROSPINAL TRACT.
Origin – Red Nucleus in
Midbrain.
Course – From Red nucleus
crosses to opposite side in lower
part of tegmentum & descend
same as Lateral Corticospinal T.
Termination – Inter Neurons
only up to upper 3 cervical
segments of cord.
Function – Facilitatory effect on
flexors & Inhibitory effect on
extensors.
Monday, May 16, 2016

26. VESTIBULOSPINAL TRACT
LATERAL VESTIBULOSPINAL TRACT.
Origin – Lateral vestibular
N(Deiter’s N)
Course – Uncrossed in Ant
Funiculus of Spinal cord.
Termination – Ventral Grey horn
neurons (VII,VIII) – through inter
neurons to α & γ neurons of lamina
IX.
Function – Receives from
vestibular apparatus utricle,
facilitate extensor, inhibit flexors &
maintain Balance. (linear)
Monday, May 16, 2016

27. MEDIAL VESTIBULOSPINAL
TRACT
Origin – Medial Vestibular
Nucleus.
Course – Uncrossed in ant
funiculus.
Termination – Ant motor
neurons or internuncial neurons
of cervical segment.
Function- Afferents from
Semicircular canal of vestibular
apparatus , to Medial
Longitudinal fasciculus control
movements of Head, Neck, Eyes in
response to Visual & Auditory
stimuli.
Monday, May 16, 2016

28. RETICULOSPINAL TRACT.
Medial Reticulospinal Tract
Origin – Medial Pontine
Reticular Formation.
Course – Descend
Uncrossed in ant funiculus.
Termination – Laminae
VII,VIII & through inter
neurons to α & γ neurons of
lamina IX.
Monday, May 16, 2016

29. LATERAL RETICULOSPINAL
TRACT.
Origin – Medullary Reticular
Formation.
Course – Uncrossed in Lateral
funiculus.
Termination – Internuncial
Neurons of Laminae VII,VIII & IX.
Function – Control Movements &
Muscle tone.
Pontine facilitate & medullary
inhibit voluntary & Reflex
Movements & Muscle tone.
Monday, May 16, 2016

30. TECTOSPINAL TRACT.
Origin – Superior Colliculi
Course – Cross midline in lower
part of Tegmentum & Descend
in Ant white funiculus
Termination – Upper cervical
segment in internuncial neurons
of Laminae V & VII.
Function – For Turning Head &
moving arm in response to
Visual, Hearing & other
Exterioceptive stimuli.
Monday, May 16, 2016

31. OLIVOSPINAL TRACT.
Origin – Inferior
Olivary Nucleus.
Course & Termination
– Descend ipsilateraly
on ant horn cells
Function - Movements
arising from
Proprioceptors.
Monday, May 16, 2016

32. MEDIAL LONGITUDINAL FASCICULUS.
Origin – From various nuclei-
vestibular N, reticular formation,
superior colliculus, interstitial N
of cajal.
Course – Closely related to
3,4,6,7 & 12
th
cranial nerve along
with Medial vestibulospinal tract.
Termination – Ventral horn cells
that innervate Neck muscles.
Function – Simultaneous
movements of Eye & Neck to
Vestibular & Auditory stimuli.
Monday, May 16, 2016

33. DESCENDING TRACTS ENDING
IN BRAIN STEM
Cortico-Nuclear tracts.
Cortico-Ponto-
cerebellar tracts.
Cortico-Rubral.
Cortico-olivary.
Cortico-reticular.
All forms part of Extra-
Pyramidal system.
Monday, May 16, 2016

34. Monday, May 16, 2016
THANK YOU.