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21 Cards in this Set
- Front
- Back
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What happens at the spinal cord?
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Output to muscles, integration of motor system components, reflex, circuitry for stereotyped motor program
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What happens at brainstem nuclei?
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Rudimentary motor control for posture, movement of trunk, head, and neck
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What happens at the motor cortex?
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Sensory information and volition is converted to a motor plan and execution
Fine motor control, conscious aspects of motor learning |
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What happens at the cerebellum?
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Coordination and motor learning, where planned movements are compared to executed movements
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What happens at the basal ganglia?
What happens if there is a lesion here? |
Overall level of motor activity is set
Results in too much or too little movement |
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How are motor neuron pools arranged?
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Ventral horn, over many spinal levels
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How does the type of muscle being controlled determine the placement of the motorneuron pool in the ventral horn?
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Proximal muscles = medial
Distal muscles = lateral Extensors = ventral Flexors = dorsal |
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What is a muscle unit?
What is a motor unit? |
Matched extrafusal muscle fibers
muscle unit innervated by an alpha motoneuron |
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What do gamma motoneurons innervate?
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intrafusal muscle fibers of spindles
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What are intrafusal muscle fibers of spindles?
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Proprioceptors that detect stretch of a muscle
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What are some muscle unit properties that characterize motor unit types?
What are these properties a function of? |
Contractile speed, fatigability
Function of myosin isotype, metabolic enzyme profile |
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What is force of a motor unit a function of?
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Numbers of muscle fibers in dfferent types of motor units
Activation frequency |
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Type S fibers
a. Speed of contraction b. Fatigability c. Force |
a. slow
b. resistant c. small |
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Type FR
a. Speed of contraction b. Fatigability c. Force |
a. Fast
b. Resistant c. More force |
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Type FF
a. Speed of contraction b. Fatigability c. Force |
a. Fast
b. Fatigable c. Most force |
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What do small motoneurons innervate?
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relatively few muscle fibers --> make up type S motor units
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How does size of motorneuron determine type of motor unit?
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Larger motoneuron innervates more fibers, makes up larger force-producing motor units
S < FR < FF |
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How does motoneuron size determine how it responds to synaptic input?
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Smaller motoneurons have higher resistance --> more depolarized for a given current --> reaches threshold faster, fires first
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When will a motoneuron begin to fire reptitively?
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At 1.5x the synaptic current necessary for recruitment
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What is motoneuron rate modulation?
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Frequency spectrum of motoneuron firing varies between its twitch force and its max tetanic tension
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What are 3 clinical hallmarks of lower motoneuron disease?
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1. Focal atrophy and wasting of muscles
2. Fasciculations (small amplitude involuntary twitch) 3. Weakness, decreased tendon reflex |
