DR NILESH KATE

MBBS,MD ASSOCIATE PROF

DEPT. OF PHYSIOLOGY

MOTOR SYSTEM

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 1, 2023

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 1, 2023

INTRODUCTION. Lower Motor Neuron

& Final Common Pathway – Alpha motor neuron & Motor nuclei of cranial nerves.

Monday, May 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

ROLE OF SENSORY RECEPTORS IN MOTOR CONTROL ACTIVITY.

Proprioceptors in skin, Muscle & joints gives feedback

& Adjust Motor

commands.

Monday, May 1, 2023

OVERVIEW TO STUDY MOTOR CONTROL SYSTEM.

Components of somatic motor control system.

Skeletal muscles: the effector organ.

Reflexes. Regulation of posture

& equilibrium.

Monday, May 1, 2023

COMPONENTS OF SOMATIC MOTOR CONTROL SYSTEM.

Highest level of motor control. Middle level of motor control. Lowest level of motor control.

Monday, May 1, 2023

HIGHEST LEVEL OF MOTOR CONTROL.

Cerebral cortex. Motor cortex. Descending motor

pathways from motor cortex.

Monday, May 1, 2023

CEREBRAL CORTEXMOTOR 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 1, 2023

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 1, 2023

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 1, 2023

TOPOGRAPHICAL REPRESENTATION OF MOTOR AREAS IN CORTEX

Monday, May 1, 2023

MOTOR HOMONCULUS

DESCENDING MOTOR PATHWAYS FROM MOTOR CORTEX.

Pyramidal tracts Extra-pyramidal

tracts

Monday, May 1, 2023

CRITERIA TO DESCRIBE TRACTS

Synonyms Origin Course Crossing Termination. Function. Applied physiology.

Monday, May 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

VESTIBULOSPINAL TRACTLATERAL 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 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

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 1, 2023

OLIVOSPINAL TRACT. Origin – Inferior

Olivary Nucleus. Course & Termination

– Descend ipsilateraly on ant horn cells

Function - Movements arising from Proprioceptors.

Monday, May 1, 2023

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 1, 2023

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 1, 2023

Monday, May 1, 2023

THANK YOU.