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25 Cards in this Set
- Front
- Back
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Motor Neurons
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Each muscle fiber is supplied by only one motor nerve fiber.
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The Motor Unit
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one nerve fiber and all the muscle fibers it innervates
behaves as a single functional unit Motor units vary in size. Muscles for eye movement have 23 muscle fibers per motor unit. The large thigh muscles have 500-1000 fibers per motor unit. "work in shifts” |
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synapse.
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The point of contact between a neuron and its target cell
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neuromuscular junction
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When the target cell is a muscle cell
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synaptic cleft
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There is a tiny gap between the two cells
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RMP is measured in mV, and is determined by
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1) diffusion of ions down their concentration gradients
2) selective permeability of the plasma membrane 3) electrostatic attraction |
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Electric potential
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potential energy that results from a polarized state.
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action potential.
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When a nerve or muscle cell is stimulated, ion gates in the membrane open, sodium ions rush in, and potassium ions rush out, resulting in changes in membrane voltage called
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Low-level tension and resistance to stretch
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Controlled by the spinal cord
Random, asynchronous motor unit contractions |
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Energy Transfer
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During exercise, muscles use energy produced by aerobic respiration and anaerobic fermentation (when oxygen is limited and lactic acid accumulates).
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For short, quick spurts of energy, muscle tissue relies on ________________ to supply ATP.
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direct phosphorylation
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Muscle fatigue, the progressive weakness and loss of contractility, is due to a variety of causes:
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ATP synthesis declines as glycogen is consumed.
The ATP usage slows down to maintain the resting membrane potential. Lactic acid lowers the pH of the sarcoplasm and impairs the action of enzymes. The accumulation of potassium ions reduces the membrane potential. Motor nerve fibers use up their Ach. The CNS fatigues for unknown reasons |
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Oxygen debt
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the difference between the resting state of oxygen consumption and the elevated rate following an exercise
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Slow-twitch fibers are small and produce twitches _______________
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up to 100 msec long
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Fast-twitch fibers are larger and produce twitches ____________
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as short as 7.5 msec
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Individuals are _______ with different ratios of slow- to fast-twitch fibers
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born
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Athletic conditioning cannot change the __________________
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genetic component of ability
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Training can only what you _________ have
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optimize
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90/10 rule
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90% of your training effort must be invested to reach the last 10% of your genetic capability.
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Muscle strength depends on
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muscle size
fascicle arrangement size of active motor units multiple motor unit summation (recruitment) temporal summation the length-tension relationship fatigue |
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Growth results mostly from ______________
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cellular enlargement
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The central nervous system occasionally triggers painful, spasmodic contractions
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cramps
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Cramps are initiated by..........
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extreme cold, heavy exercise, lack of blood flow, electrolyte depletion, dehydration, hormone imbalances, and low blood glucose
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Muscular Dystrophy
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A group of familial diseases of skeletal muscle
Usually the result of one faulty (mutated) gene Duchenne MD is the most common 1 in 3500 males (usually only in males) Lack of the dystrophin gene |
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Smooth Muscle
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Different anatomy than skeletal muscle
Wraps around blood vessels and digestive organs Controlled by the autonomic NS |
