April 26 Organization of Motor Systems

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April 26Organization of Motor Systems
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Areas of Cortex that are Important in Cortical
Control Sensorimotor Association
Cortex Secondary Motor Cortex Primary Motor
Cortex
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Sensorimotor association cortex - motor
planningA. Posterior parietal association
cortexPosition of body and external objects in
space Uses visual, auditory, and
somatosensory information to inform BB.
Dorsolateral prefrontal association cortex
makes decision to initiate response
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Secondary Motor Cortex- Receives input from
association cortex and sends output to primary
motor cortex- receives info. back from primary
motor cortex- sends output to brainstem
areas- programming of movements into complex
sequences
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Primary Motor Cortex- all prior signals related
to movement control converge here- major exit
point for motor control signals from cortex but
other routes also- somatotopically organized -
organized according to a map of the body-
mostly is dedicated to control of hands and
mouth but all of body muscles are controlled here
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Role of Basal Ganglia- modulatory role on
movement quality- no output to descending motor
pathways- modify cortical inputs and send it
back via thalamus to the motor cortex-
Parkinsons Disease due to problems here
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Role of Cerebellum-receives input from primary
and secondary motor cortex, from brainstem
output, and feedback from motor responses -
compares info. and corrects ongoing movements
that deviate from intended course- important in
control of direction, velocity, force, and
amplitude of movement and ability to adapt to
changing conditions- major role in motor
learning
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Descending Motor Pathways- 4 Pathways from
Primary Cortex to Motor Neurons of the Spinal
Cord- all descend through brainstem to spinal
cord- may be direct to spinal cord- may be
indirect - synapse in brainstem then travel on to
spinal cord or control face- many cortical
outputs control the opposite side of the body
some same some both- leave spinal cord to
control muscles
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Dorsolateral SystemsContralateral control -
opposite side Distal muscles of limbs - Arms,
legs, wrists, fingers, toes Reach and grasp
responses Independent control of fingers
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Ventromedial SystemsIpsilateral control -
same sideBilateral control - both
sides Proximal muscles of trunk and limbs
(shoulders hips) Coordinated species-typical
movements - walking running jumping
swimming
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Reflex Circuits- contained within spinal cord
and motor nerve loop- knee jerk reflex-
certain pain reflexes that requires immediate
action (burn prick)
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