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Definition
| a tissue composed of fibers capable of contracting to effect bodily movment. |
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Definition
| a contractile organ consisting of a special bundle of muslce tissue, which moves a particular bone, part or substance of the body: the heart muscle; the muscles of the arm. |
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| How are muscles cells arranged? |
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Definition
| parallel in a "muscle belly." |
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| Each muscle cell is surrounded by a covering called... |
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Definition
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Definition
| the muscle cell proper -- contains common cell properties (nucleus, mitochondria etc); contains myofibrils which contain filaments and is covered by sarcolemma. |
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Definition
| threadlike structures inside myofibril |
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| What are the components of contractile elements? |
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Definition
| filaments, made of proteins that can be thick (myosin) or thin (actin), and elastic tissue |
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Term
| what are extrafusal muscle fibers? |
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Definition
| class of muscle fibers innervated by alpha motor neurons. |
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Term
| What are alpha motor neurons? |
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Definition
| AKA lower motor neurons that control GROUPS of motor fibers. Nuclei located in cranial nerve nuclei in brainstem or nuclei located in anterior hor of spinal cord. |
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Term
| Extrafusal muscle fibers connect with alpha motor neuron called the ... |
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Definition
| neuromotor junction or motor endplate |
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Term
| extrafusal muscle fibers generate _______, do mechanical work & allow movement by contracting |
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Definition
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Definition
| the minimum unit of contraction. |
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| all ______ _____ leading to skeletal muscles have branching axons, each of which terminates in a neuromuscular junction with a single muscle fiber. |
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Definition
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Definition
| allows gradation in the force of whole muscle contractions. |
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Definition
| force is increased by increasing rate of motor unit firing. |
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Definition
| force is increased by recruiting a greater number of motor units to fire. |
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Term
| strenth of response of muscle is determined by |
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Definition
| the number of motor units activated. |
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Term
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Definition
| at rest, most skeletal muscles are in a state of partial contraction. |
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Definition
| by activating a few motor units at all times. As one set of motor units relax, another set takes over. |
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Term
| what is the function of the gamma motor neuron |
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Definition
| innervates muslce spindles (AKA: intrafusal muscle fibers)It is crucial for maintaining muscle tone |
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Term
| Where are the gamma motor neurons located? |
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Definition
| parallel to the extrfusal muscle fibers. |
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Term
| T/F; Gamma motor neurons are faster conductors |
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Definition
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Term
| What ares of the brain strongly influence the gamma motor neuron? |
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Definition
| basal ganglia, cerebellum, & indirect pathways of the CNS |
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Term
| Because of _____ ____ when a muscle is at rest, it appears neither taught nor flabby |
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Definition
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Term
| muscle tone ia manifestation of a.... |
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Definition
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Definition
| ask pt. to relax. Passively move each limb at sevveral joints to get a feeling for any resistance or rigidity that may be present. |
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Term
| gamma motor neurons (function) |
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Definition
| conatined in motor nerves; when it fires, muscle spindles shorten |
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Term
| What is the composition of a gamma loop? |
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Definition
| gamma motor neuron, muscle spindle, stretch receptor, sensory neuron, lower motor neuron, exrafusal muscle fibers. |
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Term
| What is the function of a gamma loop? |
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Definition
| adjusts muscle length reflexively relative to length of muscle spindle. |
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Term
| Damage to motor unit may include... |
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Definition
| prevents normal activation of muscle fibers, paresis, paralysis, atrophy, fasciculations, and fibrilations. |
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Definition
| loss of innervation leading to loss of muscle bulk |
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Term
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Definition
| surface twitches secondary to spontaneous motor unit discharges & lower firing thresholds: seen in motor unit disease. |
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Definition
| unable to see these, but can be detected through EMG; slow repetative firings with regular contractions secondary to lack of Lower motor neuron input. |
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Definition
| weakness; when all the alpha motor neurons supplying a single muscle are not damaged |
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Term
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Definition
| when all innervation from the LMN to the muscle are absent. |
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