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Voluntary movements
9
...
g
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A decision to move is swiftly followed by
nerve impulses travelling to the appropriate muscles to make that movement
by following the appropriate pathway
...
7
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Motor commands from cells in the grey matter
of the motor cortex initiate all voluntary movements and are modulated by
pathways from other regions, including basal ganglia and cerebellum
...
9
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GREY MATTER
of the motor cortex
WHITE MATTER
corpus callosum
BASAL
GANGLIA
internal capsule
thalamus
axons of motor
neurons
spinal cord
pyramids in
medulla oblongata
decussation in
medulla oblongata
Fig
...
17 Coronal section of the brain showing how motor pathways descend towards
the spinal cord
...
31 Walking involves more
than the simple contraction and
relaxation of antagonistic pairs
of muscles
...
Pathway of the corticospinal tract (pyramidal tract)
• Nerve impulses originate in the motor cortex, are transmitted along motor
nerve fibres and pass through the pyramids of the medulla to the cervical
region of the spinal cord (k Fig
...
18)
• Decussation (crossing over) takes place to some of the fibres before they
reach the spinal cord, while other fibres continue down to the spinal cord
• Synapses in the ventral horns of the lumbar spinal cord transmit impulses
to the spinal nerve that supplies skeletal muscles
...
9
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nerve impulses originate in the
motor cortex of the cerebrum
CEREBRUM
CEREBRUM
MIDBRAIN
MIDBRAIN
CEREBELLUM
CEREBELLUM
PONS
PONS
red nucleus
rubrospinal
tract
MEDULLA
OBLONGATA
MEDULLA
OBLONGATA
CERVICAL
SPINAL
CORD
CERVICAL
SPINAL
CORD
decussation
anterior
corticospinal
tract
skeletal
muscle
skeletal
muscle
skeletal
nerve
spinal nerve
LUMBAR
SPINAL
CORD
LUMBAR
SPINAL
CORD
lower motor neurons
Fig
...
18 Sections of the nervous system at different
levels to show the pathway of the corticospinal tract
...
9
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