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Published byBenedict Norman Thomas Modified over 6 years ago
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Muscle Contraction I Department of Biology, WCU
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Motor unit spinal cord, motor nerve, axons, axonal terminals, muscle fiber motor neuron and muscle fibers
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Motor unit Number of fibers per motor unit Small motor units
fine control (fingers, eyes) Large motor units course control (arms, legs)
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Muscle contraction 1. Muscle twitch single threshold stimulus myograph
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Muscle twitch Periods i. Latent period
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Muscle twitch ii. Period of contraction iii. Period of relaxation
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Frequency of stimulation
Short bursts Increase in frequency Further increase in frequency
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Muscle contraction 2. Isotonic contraction Muscle contracts (shorten)
muscle tension vs load Muscle contracts (shorten) Tension mostly constant (biceps curl)
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Muscle contraction 3. Isometric contraction 4. Combination
tension without contraction e.g. posture, immovable object 4. Combination movement requires both isotonic and isometric contraction
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Energetics Muscles store limited energy ATP generation
1. Creatine phosphate quick energy
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Energetics 2. Aerobic respiration O2 from Hb, myoglobin Mitochondria
slow, high energy
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Energetics 3. Anaerobic respiration Glucose from glycogen, blood
Pyruvic acid quick, low energy
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Fatigue Psychological Physiological ATP production less than usage
depletion of neurotransmitter (later lecture)
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Types of skeletal muscle
1. Red Slow contractions Color - myoglobin (more O2) Aerobic pathway Slow oxidative fibers e.g. abdominal and back muscles (posture), marathon runners
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Types of skeletal muscle
2. White Fast contractions Color - few mitochondria (only glycolysis) Anaerobic pathway Fast glycolytic fibers e.g. movement muscles (arms, legs), sprinters
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