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43 Cards in this Set
- Front
- Back
Functions of muscular system
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Movement of body, heat production, posture
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Excitability
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Ability to be stimulated
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Contractility
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Ability to contract, or shorten, and produce body movement
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Extensibility
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Ability to extend, or stretch, thereby allowing muscles to return to their resting length
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Sarcolemma
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Plasma membrane of muscle fibers
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Sarcoplasmic reticulum (SR)
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ER of muscle fibers
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Muscle fiber
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Muscle cell
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T-tubules
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Network of tubules and sacs found within muscle fibers
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Myosin
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Makes up almost all the thick filament
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Actin
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Globular protein that forms two fibrous strands twisted around each other to form the bulk of the thin filament
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Tropomyosin
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Protein that blocks the active sites on actin molecules
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Troponin
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Protein that holds tropomyosin molecules in place
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Myofibrils
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Numerous fine fibers packed close together in sarcoplasm
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Sarcomere
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Segment of myofibril between two successive Z disks
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Triad
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Triplet of tubules; a T-tubule sandwiched between two sacs of SR
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Neuromuscular junction
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Motor neurons connect to the sarcolemma at the motor endplate
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Acetylcholine
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The neurotransmitter released into the synaptic cleft that diffuses across the gap, stimulates the receptors, and initiates an impulse in the sarcolemma
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Red fibers
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Muscle fibers with high levels of myoglobin
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White fibers
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Muscle fibers with little myoglobin
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Aerobic respiration
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Occurs when adequate O2 is available from blood
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Anaerobic respiration
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Very rapid, providing energy during first minutes of maximal exercise
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Motor unit
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Motor neuron plus the muscle fibers to which it attaches
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Myography
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Method of graphing the changing tension of a muscle as it contracts
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Twitch contraction
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A quick jerk of a muscle produced as a result of a single, brief threshold stimulus
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Latent phase
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Phase of twitch contraction where the nerve impulse travels to the SR to trigger the release of Ca++
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Contraction phase
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Phase of twitch contraction where Ca++ binds to troponin and sliding filaments occur
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Relaxation phase
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Phase of twitch contraction where sliding filaments ceases
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Tetanus
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Smooth, sustained contractions
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Multiple wave summation
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Multiple twitch waves added together to sustain muscle tension for a longer time
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Incomplete tetanus
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Very short periods of relaxation between peaks of tension
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Complete tetanus
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Twitch waves fuse into a single, sustained peak
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Treppe
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The staircase phenomenon; gradual, step like increase in the strength of contraction that is seen in a series of twitch contractions that occur 1 second apart
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Tonic contraction
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Continual, partial contraction of a muscle
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Flaccid
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Muscles with less tone than normal
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Spastic
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Muscles with more tone than normal
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Muscle tone
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A small number of muscle fibers within a muscle contract and produce a tightness
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Isometric contraction
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Contraction in which muscle length remains the same while muscle tension increases; Isometric = "same length"
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Isotonic contraction
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Contraction in which the tone or tension within a muscle remains the same as the length of the muscle changes; Isotonic = "same tension"
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Concentric
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Muscle shortens as it contracts
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Eccentric
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Muscle lengthens while contracting
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Syncytium
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Continuous, electrically coupled mass (cardiac muscle)
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Single-unit (visceral) smooth muscle
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Exhibits autorhythmicity and produces peristalsis; most common type, forms a muscular layer in the walls of hollow structures; gap junctions join smooth muscle fibers into large continuous sheets
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Multiunit smooth muscle
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Each fiber responds only to nervous input; does not act as a single unit but as composed of many independent cell units
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