Motor system

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.
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11. HIGHEST LEVEL OF MOTOR
CONTROL.
 Cerebral cortex.
 Motor cortex.
 Descending motor
pathways from motor
cortex.
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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.
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15. TOPOGRAPHICAL REPRESENTATION
OF MOTOR AREAS IN CORTEX
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MOTOR HOMONCULUS

16. DESCENDING MOTOR PATHWAYS
FROM MOTOR CORTEX.
 Pyramidal tracts
 Extra-pyramidal
tracts
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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 2nd
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 & 12th
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.