Muscle Responses Twitch and Tetanus If a single electrical stimulus is

Muscle responses twitch and tetanus if a single

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Muscle Responses
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Twitch and Tetanus . If a single electrical stimulus is delivered to a muscle fiber, the fiber contracts and then fully relaxes. This single muscle response is called a twitch Sustained muscle contraction is called tetanus. Tetanic muscle contraction of many muscle fibers helps maintain posture. If the muscles that maintain our upright posture merely twitched. Recruitment - As described previously, recruitment of additional motor units increases the contractile force of a muscle. Recruitment is characteristic of the whole muscle, not a single muscle fiber. Muscle tone. Muscle tone , or tonus, refers to a normal, continuous state of partial muscle contraction. Tone is caused by the contraction of different groups of muscle fibers within a whole muscle. To maintain muscle tone, one group of muscle fibers contracts first. As these fibers begin to relax, a second group contracts. This pattern of contraction and relaxation continues to maintain muscle tone Steps in the Electrical Stimulation of Skeletal Muscle and its Contractile Response (1) The electrical signal (nerve impulse) travels down the nerve to the terminal and causes the release of the neurotransmitter ACH. (2) The ACH diffuses across the neuromuscular junction and binds to the receptor sites (3) Stimulation of the receptor sites causes an electrical impulse to form in the muscle membrane. The electrical impulse travels along the muscle membrane and penetrate deep into the muscle through the t-tubular system. (4) The electrical impulse stimulates the sarcoplasmic reticulum to release calcium into the sarcomere area. (5) The calcium allows the actin, myosin, and ATP to interact, causing cross- bridge formation and muscle contraction. This process continues as long as calcium is available to the actin and myosin (6) Muscle relaxation occurs when calcium is pumped back into the sarcoplasmic reticulum, away from the actin and myosin. When calcium moves in this way, the actin and myosin cannot interact, and the muscle relaxes. Energy Source for Muscle Contraction Muscle contraction requires a rich supply of energy (ATP). As ATP is consumed by the contracting muscle, it is replaced in three ways: 1. Metabolism of creatine phosphate. The resting muscle produces excess ATP and uses some of it to make creatine phosphate. Creatine phosphate is a storage form of energy that can be used to replenish ATP quickly during muscle contraction.
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Glycolysis . Glycolysis is a series of chemical reactions that break down glucose anaerobically (without oxygen), generating ATP. The glucose is obtained from two sources: blood glucose and the glycogen that is stored in skeletal muscle. Glycolysis provides enough energy (ATP) for an additional 30 to 40 seconds of intense muscle activity. In addition to ATP production, glycolysis also produces lactic acid. Some of the lactic acid is picked up by the blood and transported to the liver, where it is used to make glucose.
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  • Fall '19
  • muscle weakness, muscle atrophy, functions of muscles

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