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Brain Control of Movement - Coggle Diagram
Brain Control of Movement
How does the brain communicate with the motor neurons of the spinal cord? What parts of the brain communicate with one another to produce motor output?
brain → spinal cord
lateral pathways
involved in
voluntary
movement of the distal musculature and are under direct
cortical
control
corticospinal tract
:!!:
2/3 of the axons originate in areas 4 and 6 of the frontal lobe, collectively called
motor cortex
1/3 (mostly) from the somatosensory areas of the parietal lobe (to regulate the flow of somatosensory information to the brain)
pathway
motor cortex
internal capsule
cerebral peduncle (large collection of axons in the midbrain)
pons
1 more item...
rubrospinal tract :red_circle:
contributes importantly to motor control in many mammalian species, in humans it appears to be reduced
input from frontal cortex
the red nucleus of the midbrain
axons decussate in the pons
medulla
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ventromedial pathways
involved in the control of
posture
and locomotion and are under
brain stem
control.
vestibulospinal tracts
originate in the vestibular nuclei of the medulla
two components
one projects bilaterally down the spinal cord and activates the cervical spinal circuits
control neck and back muscles and thus guide head movement
another projects ipsilaterally as far down as the lumbar spinal cord
helps us maintain an upright and balanced posture by facilitating extensor motor neurons of the legs.
tectospinal tract
originates in the superior colliculus of the midbrain :world_map:
receives: direct input from the retina & projections from visual cortex & SS/Auditory afferents
After leaving the colliculus, axons quickly decussate
project close to the midline into cervical regions of the spinal cord
help to control muscles of the neck, upper trunk, and shoulders.
reticulospinal tracts
pontine
(medial)
by facilitating the extensors of the lower limbs
enhances the antigravity reflexes of the spinal cord
helps maintain a standing posture
≠
medullary
(lateral)
liberates the antigravity muscles from reflex control
arise mainly from the
reticular formation
of the brain stem
Activity in both reticulospinal tracts is controlled by descending signals from the
cortex
→ (proximal and axial muscles)
almost all of the
neocortex
involved in the control of voluntary movement
Motor Cortex
cortical areas 4 and 6
4:
primary motor cortex or M1
6:
specialized
for skilled voluntary movement (planning!)
premotor area (PMA)
connects primarily with reticulospinal neurons that innervate proximal motor units.
supplementary motor area (SMA)
sends axons that innervate distal motor units directly
pathway by which motor cortex activates lower motor neurons originates in
cortical layer V
project to cause excitation & inhibition
may generate coordinated effects on antagonist muscles
M1 neurons: encode two aspects of the movement
force and direction
population coding
Posterior Parietal Cortex
Two areas of interest
area 5
target of inputs from the primary somatosensory cortical areas 3, 1, and 2
area 7
target of higher order visual cortical areas such as MT
extensively interconnected with “
prefrontal
” areas
together represent the highest levels of the motor control hierarchy: where decisions are made about what actions to take and their likely outcome
both send axons that converge on cortical area 6
contributes most of the axons to the descending corticospinal tract
The Basal Ganglia
loop where information cycles from the cortex → the basal ganglia → thalamus → back to the cortex (SMA in area 6)
direct pathway
Cerebral Cortex
Striatum
putamen
GPi
VLo (thalamus)
indirect pathway
Substantia nigra
Subthalamic nucleus
≠
consist of
the
caudate nucleus
, the
putamen
, the
globus pallidus
(i & e) and the
subthalamic nucleus
:heavy_plus_sign:
the
substantia nigra
, a midbrain structure that is reciprocally connected with the basal ganglia of the forebrain
caudate and putamen together are called the
striatum
target of the cortical
input
to the basal ganglia
globus pallidus is the source of the
output
to the thalamus
Cerebellum
lateral cerebellum: important for limb movements.
simplest circuit
layer V pyramidal cells in the sensorimotor cortex
areas 4 and 6, somatosensory areas on the postcentral gyrus, and the posterior parietal areas
form a massive projection to clusters of cells in the pons,
the pontine nuclei
in turn feed the cerebellum
lateral cerebellum then projects back to the motor cortex
via a relay in the ventral lateral nucleus of the thalamus (
VLc
).
critical for the proper execution of planned, voluntary, multijoint move- ments.