Term
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Definition
Single motor neuron and all the muscle fiber it innervates
-Motor neuron may innervate <20 fibers or >1000 fibers
--Ratio of muscle fibers to motor neuron indicates the degree of control
---Large motor units, many muscle fibers per neuron
----Strong, gross muscle force production, but little precise control
----Example: gastrocnemius, biceps brachii
---Smaller motor units, few muscle fibers per neuron
----Weak contraction strength, but very precise control
----Example: external ocular muscles, orbicularis occuli |
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Term
| What is the innervation zone? |
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Definition
Locations where nerve terminations and muscle fibers are connected
-The placement and number of IZs are dependent on the structure and function of muscle |
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Term
| What influence does resistance and endurance training have on motor unit control behaviors? |
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Definition
Resistance- less peak firing rate
Endurance- higher peak firing rate |
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Term
| Understand the two ways we control movement |
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Definition
Recruitment- Control the firing rates of the active motor units
Rate Coding |
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Term
| What is the stretch reflex? |
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Definition
Muscle spindles
-Proprioceptor that detects changes in muscle length
-"Intrafusal" fibers => parallel to regular, extrafusals
--When muscle is stretch, these fibers length and send afferent signals to CNS
---Type la afferent fibers- direct synapse with motor neuron
--Causes the stretched muscle to contract
--When muscle has lengthened (or ceases lengthening), y-efferents contract the spindles to "reset" them
-Contributes to stretch-shortening cycle
-Protective function to prevent overstretching |
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Term
| What are the functions of muscles spindles? |
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Definition
Vibration reduces muscle spindle activity
Play a role in sense of position |
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