Term
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Definition
the combination of the motor nerve cell (neuron) and all the muscle cells it innervates
a. When an electrical impulse travels down the axon, all muscle cells attached to the motor unit contract simultaneously
2. Recruitment: the more muscle units recruited, the more force can be generated
B. Fine Motor Control
1. Ratio of neuron to muscle cell is smaller for fine motor control
a. Ex. Muscles of eye: 1(neuron):23(muscle cells)
2. Ratio of neuron to muscle cell is larger for general/coarse
a. Ex. Gastrocnemius: 1(neuron):1000(muscle cells) |
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Term
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Definition
| individual stimulus results in a twitch |
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Term
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Definition
| temporal summation/recruitment |
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Term
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Definition
a. Incomplete/Unfused Tetanus: stays maximally contracted, but little moments of relaxation; APs are synchronized
b. Complete/Fused Tetanus: maximally contracted and muscle does not completely relax, but graph comes out smooth; APs are unsynchronized |
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Term
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Definition
1. Isotonic: muscle contracts, shortens, and creates enough force to move the load
a. Moving load in smooth even manner
b. Constant tension with shortening
2. Isometric: muscle contracts but does not shorten
a. Tension without shortening, force still generated
3. Concentric: shortened in the same direction of the contraction
4. Eccentric: lengthens/extending in the opposite direction of contraction |
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Term
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Definition
1. A muscle fiber contains only enough ATP to power a few twitches
2. The body take about 2 min to adjust O2/glucose delivery at the beginning of exercise
3. Its ATP “pool” is replenished as needed from several supplemental sources. |
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Term
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Definition
1. Creatine Phosphate
a. Enough to provide about 10-20 seconds worth of contractions
b. Creatine phosphate + ADP ↔ creatine + ATP
2. Glycogen Breakdown (anaerobic)
a. Skeletal muscle fibers contain about 1% glycogen
b. Glycogen broken down via glycogenolysis
3. Cellular Respiration (in the mitochondria of the fibers)
a. Sustained supply of ATP during exercise
b. 30-32 ATP produced per glucose, max is 38
i. Glycolysis(in cytosol): 2 ATP by substrate-lever phosphorylation
ii. Krebs Cycle (in mitochondria): 2 ATP by substrate-level phosphorylation
iii. Electron Transport Chain (in mitochondria): ~ 34 ATP by oxidative phosphorylation |
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Term
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Definition
1. Single-unit smooth muscle is connected by gap junctions and the cells contact as a single unit
2. Multi-unit smooth muscle cells are not electrically linked and must be stimulated independently |
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Term
| Smooth Muscle Contraction (overview) |
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Definition
1. Actin and myosin are loosely arranged around the periphery of the cell, held in place by protein dense bodies
2. The arrangement of the fibers causes the cell to become globular when it contracts
a. Some do not need external stimulus; some stimulate itself
3. Myosin can slide along actin for long distances without encountering the end of a sarcomere.
4. Smooth muscle myosin has hinged heads along its length |
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Term
| Smooth Muscle Contraction (in depth) |
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Definition
1. Intracellular Ca2+ concentrations increase when Ca2+ enters cell and is released from SR
2. Ca2+ binds to calmodulin (CaM)
a. Calmodulin acts as a regulatory protein; no troponin or tropomyosin present
3. Ca2+–calmodulin activates myosin light chain kinase (MLCK)
4. MCLK phosphorylates light chains in myosin heads and increases myosin ATPase activity
5. Active myosin crossbridges slide along actin and create muscle tension |
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Term
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Definition
a. Time it takes for AP to be received from CNS
b. AP from CNS → muscle AP → development of tension during one muscle twitch |
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Term
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Definition
a. Skeletal: fastest
b. Cardiac: slight lag time
c. Smooth: longest lag time, but tension sustained the longest |
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