The reacting mechanism - the muscles and glands comprise this reacting mechanism. A. Muscles are of three kinds: 1. Voluntary, stripe, skeletal or unstriated 2. Involuntary, visceral, smooth or unstriated 3. Cardiac or heart The characteristics of muscles are: 1. Contractility is the power of muscles to shorten 2. Tonicity is the power to be in partial contraction 3. Extensibility is the power of muscles to stretch. 4. Elasticity is the power to resume its original shape. The functions of muscles are: 1. To lend share to the body as the skeletal or voluntary muscles of the arms and legs do. 2. To propel food and waste products along the intestinal pathway as smooth muscles in the digestive tract do 3. For movement as when the arms and legs move or when we move the mouth to form the sounds of speech. 4. To control the flow of blood, automatically opening and closing the blood vessels in response to body needs. 5. To convert mechanical energy into mechanical work. 6. To generate heat. Facts about muscles: 1. Muscle fibers connot be manufactured - the growth of a muscle results from an increase in the size of individual muscle cells - hence, the kind of exercise is important. 2. The principal source of muscle energy is glucose - obtained from sugar, starches and carbohydrates. 3. The flow of acetylcholine ions stimulate muscular contraction. 4. Repeated movements requiring less than maximum strength increase the blood supply, and therefore the endurance but not the size of the muscle. The speed of reaction of muscles depends upon certain factors: 1. Condition of nerve pathways - whether blocked or open 2. Condition of the muscles - whether relaxed or fatigued 3. Strength of the stimulus B. Glands are special secreting organs which soup their secretions either directly or indirectly into the bloodstream.
Posted on: Tue, 25 Jun 2013 21:52:33 +0000
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