Control of Motor

System by Brain stem

DR. SUMERA GUL

ASSOCIATE PROFESSOR

DEPARTMENT OF PHYSIOLOGY

Learning Objectives

At the end of the lecture the students should be

able to:

Discuss the physiologically important parts of brain

stem.

Explain the motor functions of the brain stem

Elucidate the excitatory-inhibitory antagonism

Brain stem

Comprises of?

Functions?

Functions

Control functions of :

Respiration

CVS

GIT

Equilibrium

Ocular movements

Relay station

Site of origin of cranial nerve nuclei

Reticular formation

Alertness

Motor Control by Brain stem

RETICULOSPINAL TRACT

Pontine Reticulospinal tract :

Excitatory to Axial extensor muscles

Medullary reticulospinal tract: Inhibitory to axial extensor Muscle

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RETICULOSPINAL TRACT

Pontine Reticulospinal tract :

Excitatory to Axial extensor muscles

Very strong natural stimulus

Receive input from cerebellum and vestibular nuclei

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RETICULOSPINAL TRACT

Medullary reticulospinal tract: Inhibitory to axial extensor Muscle

Receive input from corticospinal tract, rubrospinal tract and other motor pathways

These normally activate the

medullary reticular inhibitory system

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some signals from higher areas of the brain can

“disinhibit” the medullary system when the brain

wishes to excite the pontine system to cause

standing.

The medullary system and the pontine system

work in antagonistic

VESTIBULOSPINAL TRACTFunction - Excitatory to

ipsilateral extensor. Inhibitory to flexors muscles

Regulates muscle tone for maintaining balance in response to head movement

Selectively control the excitatory signals in response to vestibular apparatus

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VESTIBULOSPINAL TRACT

transmit strong excitatory

signals to the antigravity

muscles

Without this support, the

pontine reticular system would

lose much of its excitation

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Decerebrate Rigidity

If brain stem is sectioned below Mid section of

midbrain..

Medullary, pontine and vestibular system

remains inact

There will be rigidity in extensors

Why?