Muscles

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Muscles are made up largely of protein and consist of a large number of very long cells known as muscle fibresbound together by connective tissue. They contract to do work and when they relax can be pulled back to their original length. Muscles have a good blood supply to provide them with the glucose and oxygen they need for energy. Muscles repspond to stimulation from the nervous system and to chemical stimulation. Muscles can make up to 40% of the body weight and there are 3 types of muscle, striated, smooth and cardiac. You only need to know about striated muscle, which is the muscle attached to the skeleton. It is under the control of the voluntary nervous system and contracts quickly, but tires relatively quickly. Muscle fibres are made up of many myofibrils lying parallel to each other. Each is made up of sarcomeres and the proteins actin and myosin make up a large part of the sarcomeres. The cytoplasm of the myofibrils is called sarcoplasm. It contains a lot of mitrochondria and the sarcoplasmic reticulum. Muscle cells also contain myoglobin which is a protein similar to haemoglobin, but has a much higher affinity for oxygen and so acts as a store in muscles. There are 2 types of skeletal muscle fibres which give different levels of performance. 

  • Slow twitch muscle fibres - adapted for steady action over a period of time. They contract relatively slowly. They maintain your body posture and have a rich blood supply.
  • Fast twitch muscle fibres - contract very rapidly and are…

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