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Chapter 14

NROC64H3 Chapter Notes - Chapter 14: Vestibular Nuclei, Striatum, Lobe (Anatomy)


Department
Neuroscience
Course Code
NROC64H3
Professor
Matthias Niemeier
Chapter
14

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Chapter 14 Brain Control of Movement
Introduction
- Final common pathway for behaviour is alpha motor neuron, and this activity is under the control of sensory
feedback and spinal interneurons, and that reflex movements reveal the complexity of spinal control system
- Central Motor System is arranged as hierarchy of control levels, FOREBRAIN-TOP, SPINAL CRD-BOTTOM
Highest level: Association areas of neocortex and basal ganglia STRATEGY: goal of movement and
movement strategy that best achieves the goal
Middle level: Motor cortex and cerebellum TACTICS: sequences of muscle contractions, arranged in
space and time, required to smoothly and accurately achieve the strategic goal
Lowest level: Represented by stem brain and SC EXECUTION: Activate motor neuron and interneuron
pools to generate goal-directed movement and make necessary adjustments of posture
- i.e. Baseball pitcher. Neocortex has information (senses), strategies need to be devised to move body to make
options, which are filtered through BG and back to cortex until final decision. Motor areas of cortex and cerebellum
make tactical decision and issue instructions to BS and SC. Activation of neurons in BS and SC cause movement to
be executed
Descending Spinal Tracts
- Axons descend brain through SC through 2
major groups of pathways:
1. Lateral pathway: Voluntary movement of
distal musculature, under DIRECT cortical
control
2. Ventromedial pathway: Control of posture
and locomotion, under brain stem control
The Lateral Pathways
- Most important = corticospinal tract: longest
and large CNS tract
2/3 of axons in motor cortex = area 4 and 6
in frontal lobe
Rest of axons in corticospinal tract from
somatosensory areas of parietal lobe to regulate flow of somatosensory information to brain
Axons pass through internal capsule cerebral peduncle (lost of axons in midbrain) pons forms bulge
called medullary pyramid (corticospinal’s tract cross section is triangular is called the pyramidal tract
Pyramidal tract crosses/decussate CONTRALATERAL THINGS axons collect in lateral and form lateral
corticospinal tract terminate in dosrsolateral region of ventral horn and intermediate gray matter (control
distal muscle, particularly flexors)
Rubrospinal tract, which originate in red nucleus of midbrain: named for pinkish hue (Latin rubro-red),
Axons decussate in pons and join to corticospinal tract in lateral column

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Major source of input is frontal cortex
that contributes to cortico spinal tract
The Effects of Lateral Pathway Lesions
- Modern view of function of lateral pathways: late
1960s by Donald Laqrece and Hans Kuypers
- Experiential lesions in corticospinal and
rubrospinal trac tin monkey making them unable
to make fractionate movements of arms and
hands (couldn’t move shoulders, elbows, wrists
and fingers independently(
i.e. could grasp small objects but couldn’t’ move
shoulders only by using all fingers at once
- Lesions caused movement deficit but many
functions gradually reappeared over month of
surgery (only permanent deficit was weakness of
distal flexors and inability to move fingers
independently)
- Corticorubrospinal pathway was able to partially
compensate for the loss of cortico tract input
-Strokes in damage to motor cortex or
corticospinal tract = paralysis on contralateral side,
but considerable recovery of voluntary movements
may occur over time
Box 14.1: Of Special Interest: Paresis, Paralysis, Spasticity and Babinski 488
- Damage to lower parts of motor system alpha motor neurons or motor axons leads to consequences
Partial damage = paresis/weakness
Complete severing of motor nerve = paralysis/loss of movement of affected muscles and areflexia/absence of
spinal reflects
Muscles have no tone/resting tension = flaccid and soft
- Damage to upper parts of motor system motor cortex and motor tracts cause different motor problem
Common after a stroke damages regions of cortex or brain stem, injury or Demyelinating disease
Period of spinal shock: reduced muscle tone/hypotonia, areflexia, and paralysis called hemiplegio/one of side
body, paraplegia/involve only legs, quadriplegia/involved all 4 limbs
Spasticity can set in, often permanently, characterized by dramatic and sometimes painful increase of muscle
tone/hypertonia, and spinal reflexes/hyperreflexia, overactive stretch reflexes cause clonus/rhythmic cycles of
contraction and relaxation
Indicator of motor tract damage is Babinski sign: Babies would curl toes downward when scratching sole
of foot form heel toward
The Ventromedial Pathways
- Contains 4 descending tracts that originate in brain stem and terminate among spinal interneurons controlling
proximal and axial muscles
- Vestibulospinal tracts come from vestibular nuclei in medulla which relay sensory information from
vestibular labyrinth in inner ear
Labyrinth has fluid-filled canals in temporal bone closely related w/ cochlea, motion of fluid activates hair cells
that signal nuclei via cranial nerve VIII
Tract projects bilaterally down SC and activates spinal circuits that control neck and back muscles and guide
head movement (Head stability important)
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