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Muscle Physiology Skeletal muscle function

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Muscle Strength A motor unit is one motor neuron and all of the muscle fibers it controls The force with which a whole muscle contracts depends on how many motor units the nervous system stimulates.

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All or None.. A muscle will either completely contract, or not at all. This means the stimulus only needs to pass the threshold.

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What is the threshold? The minimum amount of stimulation that will cause a muscle fiber to completely contract. The amount of work that a muscle is being asked to perform is directly proportional to the threshold of the stimulus.

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Types of muscle contractions Isometric: Muscle increases in tension but does not shorten Isotonic: The muscle shortens and the amount of tension is constant. Most muscle movement is a combination of both types of contractions.

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Muscle Fatigue Fatigue is the decrease in ability to do work Psychological fatigue is when a person thinks he/she cannot do any more muscular work Muscle fatigue means the muscles have trouble, or are unable to respond to stimuli

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Energy for muscle contraction Creatine phosphate can be used as an energy source for ATP production. Most ATP is produced during aerobic respiration

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Oxygen and exercise Heavy exercise creates EPOC excess post- exercise oxygen consumption The time spent in EPOC depends on each persons level of fitness Fat metabolism is also a factor because more oxygen is required to generate energy from fats

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Hypertrophy and Atrophy Hypertrophy is an increase in a muscles size Most hypertrophy is due to exercise Atrophy is a decrease in muscle size This is usually due to disuse.