1. Brain Stem Motor Function
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brain stem

2. Neural centers for control of movements
Motor cortex
Basal ganglia
Brain Stem
cerebellum
Spinal Cord
Skeletal muscles
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brain stem

3. Functional Anatomy
Brain stem in the physiological sense is comprised of
Medulla, Pons, Mesencephalon (midbrain)
Neuronal circuits within this area control many physiological functions
BP, respiration, body temp, sleep & wakefulness, GIT
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brain stem

4. Functional Anatomy Control of physiological functions
Stereotyped movements of the body
Equilibrium and balance
Eye movement
In addition Reticular formation (RF) and Vestibular Nuclei
Important components of motor control system
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brain stem

5. Functional Anatomy Serves as a way station for
Command signals from higher neural centres that command the brain stem to
Initiate, modify specific control functions throughout the body
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brain stem

6. Brain Stem Motor Centers
Red nucleus
Midbrain
Vestibular nucleus
Pons
Pontine Ret. formation
Medullar Ret. formation
Medulla oblongata
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brain stem

7. Brain Stem Motor centres Red nucleus
Lateral vestibular nucleus (Deiter’s nucleus)
Certain parts of reticular formation in pons and medulla oblongata
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brain stem

8. Motor centres Have efferent fibres that influence motor pathways in
Spinal cord
Cranial motor nerves
Form part of efferent pathways from higher motor centres
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brain stem

9. The Red Nucleus Lie in the midbrain Receive signals from the
Motor cortex, Cerebellum
Project signals to the spinal cord: Rubro-Spinal Tract (RUST)
Stimulation of the system
Excitation of Flexors
Inhibition of extensors
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brain stem

10. Red Nucleus RUST crosses over the opposite side
Runs through the spinal cord close to CST
Connect to MN
Inhibit extensors
Excite flexors
Red nucleus
RUST
Extensors
+ Flexors
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brain stem

11. Reticular Formation Brain stem reticular formation
Two areas with motor control activity
Pontine reticular nucleus
Medullar reticular nucleus
Give rise to reticulospinal tracts
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brain stem

12. Reticular formation The two sets of nuclei
Function antagonistically to each other
Pontine exciting the Antigravity muscles
Medullary inhibiting them
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brain stem

13. Pontine Reticular Nucleus
Located in the pons, extends to midbrain
Transmit excitatory signals down the spinal cord
Pontine (medial) Reticulospinal tract (M-REST)
Terminate on MN
Excite extensors (antigravity)
Inhibit flexors
+ Extensors
- Flexors
M-REST
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brain stem

14. Pontine Reticular Nucleus
Pontine (medial) Reticulospinal tract (M-REST)
Also excite
Axial muscles which support body against gravity
Muscle of the vertebral
Extensor muscles of limbs
+ Extensors
- Flexors
M-REST
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brain stem

15. Pontine Reticular Nucleus
Cells of the Pontine R.N have
High degree of excitability (inherent)
Excitability is held in check by
Inhibitory signals
Cerebral cortex
Basal ganglia
Cerebellum
Cerebral cortex, basal ganglia, cerebellum
Vestibular N., Cerebellum
Inhibitory signals
Excitatory signals ++
- -
Pontine R.N
Muscle spaciticity
+ +
α MN, γ MN excitability increases
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brain stem

16. Pontine Reticular Nucleus
Receive excitatory signals from
Vest. Nucleus
Cerebellum (deep nucleus)
If unopposed by medullary syst
Causes powerful excitation of antigravity muscles
SPACITICITY
Cerebral cortex, basal ganglia, cerebellum
Vestibular N., Cerebellum
Inhibitory signals
Excitatory signals ++
- -
Pontine R.N
Muscle spaciticity
+ +
α MN, γ MN excitability increases
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brain stem

17. Medullary Reticular Nucleus
Medullar reticular Nucleus
Located in the reticular area of medulla
Transmit inhibitory signals down the spinal cord
Medullar (lateral) Reticulospinal tract (L-REST)
Connect to MN
Inhibit extensors
Excite flexors
L-REST
Extensors
+ Flexors
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brain stem

18. Medullar Reticular System
Receive strong imputes by way of collaterals from CST, RUST, other motor pathways
These normally activate the medullar inhibitory system
This counteracts the excitatory effects of Pontine reticular system
Pontine R.N
CST, RUST, other motor pathways ++
Medullar R.N
- - ++
α MN, γ MN
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brain stem

19. Medullar Reticular System
Medullar R.N
Can also receive inhibitory imputes by way of collaterals from CST, RUST, cerebellum
These normally inhibit medullar inhibitory system
When the brain wishes to cause excitation of Pontine reticular system, to facilitate standing
Pontine R.N
CST, RUST, other motor pathways ++
- -
CST, RUST cerebella ++
α MN, MN
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brain stem

20. Vestibular Nucleus Located in the pons and medullar
Project to spinal cord
Vestibulospinal tract (VEST)
Connect to MN
Excite extensors
Inhibit flexors
+ Extensors
- Flexors
VEST
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brain stem

21. Vestibular Nucleus
Vestibular Nucleus
Provide strong excitatory signals to antigravity muscles
Selectively control the excitation of different antigravity muscles
To maintain equilibrium and balance in response to vestibular apparatus
+ Extensors
- Flexors
VEST
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brain stem

22. Brain Stem Motor Effects
CST
RUST
L - REST
VEST
Flexors excited
Extensors inhibited
M- REST
Flexors inhibited
Extensors excited
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brain stem