Skeletal Muscle
• Long cylindrical cells• Many nuclei per cell• Striated• Voluntary• Rapid contractions
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Cardiac Muscle
• Branching cells
• One or two nuclei per cell
• Striated
• Involuntary
• Medium speed contractions
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Smooth Muscle
• Fusiform cells
• One nucleus per cell
• Nonstriated
• Involuntary
• Slow, wave-like contractions
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Muscle Contraction Summary
• Nerve impulse reaches myoneural junction
• Acetylcholine is released from motor neuron
• Ach binds with receptors in the muscle membrane to allow sodium to enter
• Sodium influx will generate an action potential in the sarcolemma
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Muscle Contraction Continued
• Action potential travels down T tubule
• Sarcoplamic reticulum releases calcium
• Calcium binds with troponin to move the troponin, tropomyosin complex
• Binding sites in the actin filament are exposed
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Muscle Contraction Continued
• Myosin head attach to binding sites and create a power stroke
• ATP detaches myosin heads and energizes them for another contaction
• When action potentials cease the muscle stop contracting
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Motor Unit Ratios
• Back muscles– 1:100
• Finger muscles– 1:10
• Eye muscles– 1:1
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Creatine
• Molecule capable of storing ATP energy
Creatine + ATP Creatine phosphate + ADP
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Creatine Phosphate
• Molecule with stored ATP energy
Creatine + ATPCreatine phosphate + ADP
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Muscle Fatique
• Lack of oxygen causes ATP deficit
• Lactic acid builds up from anaerobic respiration
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Muscle Atrophy
• Weakening and shrinking of a muscle
• May be caused– Immobilization– Loss of neural stimulation
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Muscle Hypertrophy
• Enlargement of a muscle
• More capillaries• More mitochondria• Caused by
– Strenuous exercise
– Steroid hormones
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Tetany
• Sustained contraction of a muscle
• Result of a rapid succession of nerve impulses
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Refractory Period
• Brief period of time in which muscle cells will not respond to a stimulus
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Isometric Contraction
• Produces no movement
• Used in– Standing– Sitting– Posture
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