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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
9
RETICULOSPINAL TRACT
Pontine Reticulospinal tract :
Excitatory to Axial extensor muscles
Very strong natural stimulus
Receive input from cerebellum and vestibular nuclei
10
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
12
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
15
VESTIBULOSPINAL TRACT
transmit strong excitatory
signals to the antigravity
muscles
Without this support, the
pontine reticular system would
lose much of its excitation
16
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?