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Lecture 13

SPHR 2106 Lecture Notes - Lecture 13: Convolution, Cerebellar Vermis, Withdrawal Reflex


Department
Speech and Hearing Science
Course Code
SPHR 2106
Professor
Schulz
Lecture
13

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Movement Control
Spinal Control of Movement: contralateral
Bulbar Control of movement: bilateral
Limb movement: determined by agonist/antagonist muscle pairs
Motor Control Hierarchy
Lowest: spinal cord and brain stem
Middle: motor cortex, cerebellum
High: Association areas of cortex, basal ganglia
Major muscles of elbow joint
When contract bicep, arm flexes
Contract tricep, arm extends
Muscle innervation by lower motor neuron
Corticospinal tract neurons come down and synapse with spinal motor nerves out of ventral
horn to innervate striated muscle of arms and legs
Lower motor neurons: peripheral nerve that come out of ventral root
Alpha motor neurons
Each muscle fiber is innervated by a single axon
Motor unit is defined as an alpha motor neuron and all muscle fibers it innervates
Motor neuron pool: all the alpha motor neurons that innervate one muscle
To control fine motor movement: more motor units
Innervation Ratio=number of muscle cells per motor neuron
Low for fine motor control and high for gross motor control
Fewer muscle fiber innervated by a single axon: more discrete kinds of movement
Muscle that need to be quickly and finely moved have very few muscle fibers innervated per
alpha motor neuron
High innervation ratio: forceful movements
From muscle twitch to sustained contraction
Excitatory postsynaptic potential: neurotransmitters open gates to let in positive ions,
have to reach threshold to generate action potential
A single action potential in an alpha motor neuron causes a twitch and not a full
contraction
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