Preksha Dhyana Human Body Part 2

Author(s): Jethalal S Zaveri
Publisher: Jain Vishva Bharati

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more often left its young victims crippled for life with paralyzed limbs and withered muscles. The development of effective vaccines against the polio virus has nearly wiped out the disease. Parents are advised to get their children immunized against polio in good time to prevent the onslaught of the disease.
For an understanding of such disorders of the muscular system, the following concept is of key importance. The functioning unit of a muscle is not the individual muscle-cell but rather the motor unit-the combination of a motor nerve and the muscle fibres that it innervates. Anything that damages either the muscle or the nerve may result in a loss of muscle-function. Thus polio is not a disorder of the muscles in the first place, but a disease of the nervous system in which the virus infection can destory the neurons. The muscle atrophy (wasting or withering) that often follows the disease is a result of the disuse of the muscle innervated by the damaged neurons or controlled by a damaged centre in the brain stem. The treatment includes regular exercising of the affected muscles.
Atrophy, Hypertrophy and Dystrophy
Muscles tend to atrophy (waste away) with disuseeither in paralysis or due to continued inactivity. When muscles are subjected to prolonged vigorous contractions, the opposite occurs. They hypertrophy i.e. grow larger. As far as the skeletal muscles are concerned, gradual enlargement is not a disorder but a positive change making them stronger and more effective. The key to body-building is to progressively increase the load on the muscles; regular exercise will not produce hypertrophy, if maximum contractions are not involved. The aim of exercise is to condition the muscles and keep them ready for use and not to tire them.
Hypertrophy is a pathological condition for the heartmuscle. Heart tends to enlarge when it is overworked, e.g. when arteries are clogged with fatty deposits. The resulting increased force of contraction may cause great discomfort.
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