Term
| Lower Motor Neuron Control |
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Definition
Innervate skeletal muscles.
Directly controlled by Local Circuit Neurons.
Indirectly controlled by Upper Motor Neurons. |
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Term
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Definition
| feedback system that monitors and maintains muscle length |
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Term
| Lower Motor Neurons (LMN) |
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Definition
| neurons which send their axons out of the brainstem and spinal cord to innervate the skeletal muscles of the head and body, respectively |
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Term
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Definition
| all motor neurons innervating a single muscle |
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Term
| Gamma Motor Neurons (yMN) |
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Definition
| small LMNs which innervate specialized muscle fibers; regulate the sensory input by setting infrafusal muscle fibers to an appropriate length. the gain of muscle spindles so they can operate efficiently at any length of the parent muscle |
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Term
| Alpha Motor Neurons (aMN) |
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Definition
| innervates the extrafusal muscle fibers which are the striated muscle fibers that generate forces needed for posture and movement |
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Term
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Definition
| : sensory receptors embedded with connective tissue capsules in the muscle comprised of yMNs and nerve fibers |
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Definition
| a single aMN and its associated muscle fibers which constitute a unit of force activated to produce movement |
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Term
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Definition
the sensory signal originates in the muscle spindles (8-10 intrafusal fibers in parallel with extrafusal fibers making up bulk of muscle)
1. stretch imposed on the muscle deforms the intrafusal muscle fibers
2. initiation of action potentials mechanically gated ion channel activation in afferent axons coiled around spindle |
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Term
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Definition
| Large-diameter sensory fibers coiled around the central part of the spindle; mediate rapid reflex adjustments when the muscle is stretched |
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Term
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Definition
| inhibitory connections with the α motor neurons of antagonistic; results in rapid contraction of stretched muscle and simultaneous relaxation of antagonist muscle |
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Term
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Definition
i. Sensory receptor initiates the stretch reflex
ii. Stretching muscle spindle leads to increased activity in the Ia afferents and increase in aMN activity innervating same and synergist muscles; inhibit aMN that innervate antagonist
iii. negative feedback loop used to maintain muscle length at a desired value |
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Term
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Definition
| the steady level of tension in muscles |
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Term
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Definition
the level of excitability of aMN that serve as the efferent side of reflex loop: v. When aMN stimulated without yMN activation, Ia fiber response decreases as muscle contracts
vi. When both aMN and yMN activated, no decrease in Ia firing during muscle shortening |
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