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Lecture 2

KIN 155 Lecture Notes - Lecture 2: Supplementary Motor Area, Premotor Cortex, Substantia Nigra

Course Code
KIN 155
Fran Allard

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Lecture Two – Motor Cortex
neural signals --> muscle contraction --> movement
signals comes from Brain => spinal cord => motor neurons => muscle
variations of movements comes from different levels of contraction + change in
muscle length
CNS = brain + spinal cord
oVoluntary movements are produced by CNS
oimportant component for movement are:
cerebral cortex
basal ganglia
spinal cord
CNS generates control signals to muscle (efference);
and evaluates sensory feed back (afference)
cerebral cortex --> 2 hemispheres: each divided into 4 lobes:
1. frontal lobe
2. parietal lobe
3. occipital lobe
4. temporal lobe
cortical areas responsible for motor control are:
omotor cortex
opremotor cortex
osupplementary motor area
all located in the frontal lobe
motor cortex and somatosensory show topographic or somatopic organization
electrical stimulation of motor cortex results in movement of the body part
controlled @ that location --> neurons of motor cortex communitcates w/ motor
neurons in spinal cord
damage in motor cortex produces weakness in the muscle controlled by that area
the size of the area of motor cortex controlling a particular limb can change w/
oie. expert badminton player's forearm
Somatosensory cortex is located behin the motor cortex and is:
responsible for sensing touch + position of body
also organized somatopically but homuculus is different from motor cortex
Also modifiable be experience: ie. Left hand area of violin player

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Lecture Three - Sub-cortical Structures
Somatosensory Cortex (S1)
located behind the motor cortex in the parietal lobe
responsiblefor perceiving sensory information from touch ad proprioception
arranged somatopically, with different sized areas for sections of the body than
found in the motor cortex; shown in a homuculus diagram
ostring player's somatosensory area found larger at the left hand area; area
also increases as the player starts from an earlier age (learning can modify
the somatosensory cortex)
Premotor cortex
located in front of primary motor cortex
important role in selection and preparation of a movememt (planning of a
oif damaged --> inability to plan strategy for a movement [condition in
human: apraxia]
mirror neurons – important fo the ability to learn a skill by watching another
person and understanding their intention; important for social abilities
Supplementary Motor Area (SMA)
located infront of primary motor cortex, above premotor cortex
responsible for programming sequences of movements
coordination of both hands
odamage to SMA causes inabilily for hands to work togther
the premotor and supplementary motor areas both work THROUGH the motor
obut cannot produce movements on their own
Additional Cortical motor control centres are
Premotor cortex, important for movement selection and preparation, especially
imvolved in when movement involves a response to visual cue
othe location of mirror neutons
osupplementry motor area (SMA), important in production of movement
Next -> subcortical motor control structures the cerebellum and the basal ganglia

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Lecture Four - More Subcortical Structures
1. the cerebellum means “little brain” in latin
o10% of the brain by weight, but contains more than half the neurons
oworks as an indirect controller of movement: does not directly produce
movement like motor cortex, but is important in both production and
ohas 3 major function sections
1. vestibulocerebellum: important in control of eye movement and
body equillibrium during stance and gait
2. Spinocerebellum: important in execution of an on-going movement
– it adjusts movements so that they occur as planned
3. cerebrocerebellum: important in the timing and initiation of
ocerebella diseases or damaged can produce
1. disruption to the comtrol of limb and eye movements
2. impaired balance
3. decreased muscle tone
4. tremor(osillation) while moving, especially at the end of a
oThus the cerebellum makes a movement happen as planned.
oIt can do this because:
it gets information about the plan/ intention of the movment from
the cortex
it gets sensory info from ongoing movement
it projects to the descending motor control system and can
influence how a movement is produced
recent research suggests the cerebellum is important for motor
2. the basal ganglia
omade up of 5 subcortical nuclei:
1. caudate
2. putamen
3. subthalamic
4. globus pallidus
5. substantia nigra
osimilar to cerebellum, acts as an indirect controller: nuclei get input from
the entire cortex and send otputs into prefrontal and premotor cortex
through the thalamus
odisorder here produce major movement problems: huntinton's disease and
parkinson's diease
parkinson's is caused by a deficiency in the neurotransmitter
dopamine b/w thr substantia nigra and the striatum
symtoms are rhythmic tremor at rest
increased muscle tone or rigidity
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