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10 Cards in this Set
- Front
- Back
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Smooth Muscle
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Innervated by autonomic NS, plays role in peristalsis and blood pressure/flow
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Muscle Fiber
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Cells of skeletal muscle, each innervated by one axon branch from the CNS
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Alpha Motor Neurons
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Directly trigger generation of muscular force by releaseing ACh at the neuromuscular junction. Size principle: variations in size conribute to orderly motor neuron recruitment.
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Fast Motor Units vs. Slow Motor Units
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FMUs contain bigger motor neurons and larger-diameter, faster-conducting axons, and rapidly fatiguing white fibers. 30-60 impulses/s sporadically
SMUs: smaller motor neurons, slower axons, larger number of Mitochondria and oxidative enzymes. 10-20 impulses/s more steadily |
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Sarcoplasmic Reticulum
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Extensive intracellular sac that stores Ca2+ and releases it during excitation-contraction coupling
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T (transverse) Tubules
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Permit action potentials access to the SR by means of its voltage-sensitive tetrads (four calcium channels). The tetrads open the calcium release channel in the SR membrane and the newly free Ca+2 within the cytosol makes the myofibril contract.
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Sliding-filament model of sarcomere shortening
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Thick filament myosin binds to thin filament actin in the presence of Ca2+, causing pivot of thick filaments with respect to thin filaments.
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Duchenne Muscular Dystrophy
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Afflicts mainly adolescent boys who lack mRNA encoding dystrophin, which leads to secondary changes in contractile apparatus causing muscle degeneration.
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Muscle spindles and Ia sensory axons
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Spindles, also called stretch receptors, contain muscle fibers in a fibrous capsule with Ia axons wrapped around them which are the largest and fastest axons and synapse on nearly every alpha motor neuron in the neuron pool of a muscle.
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Myotatic (stretch) Reflex
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Sensory feedback mechanism by which Ia axon discharge rate is correlated with the length of the muscle at a point in time. When tension is placed on a muscle, the AMNs respond by increasing action potential frequency, causing a contraction.
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