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| Muscular Tissue |
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| Nature, Occurrence and Function: |
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| Muscles of the body are made up of elongated muscle cells also known as muscle fibre. The movement of the body is brought about by the contraction and relaxation of contractile protein present in muscle cells. There are three type of muscle fibres. |
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| Striated muscle fibres |
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| These are striped muscles and are voluntary since their contraction is under the control of the will. The entire muscle fibre shows alternate dark and light patches. They are long cylindrical unbranched cells, with a number of nuclei, which are situated towards the periphery of the muscle fibre. These muscle fibres are found in the muscles of the limbs, body wall, face, neck etc. The function of these muscles is to provide locomotion and all other voluntary movements to the body. |
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| Unstriated muscles |
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| These are smooth, involuntary muscles. Each muscle fibre is a long, narrow, spindle shaped tapering cell. The cell is uninucleate. Delicate threads called myofibrils run longitudinally through the cell. These muscles are found in the walls of the alimentary canal, and internal organs. Unstriated muscles cause slow and prolonged contractions, which are involuntary i.e. not under the control of the will. In the alimentary canal they cause movement of the food and in the blood vessels they help the blood to flow. |
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| Cardiac muscle |
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| Cardiac muscles are extensively present in the heart. They show characteristics of both striated and unstriated muscles. They are composed of non-tapering cells with faint cross striations. Each cell contains one or two nuclei. The cells are cylindrical and branched. The function of the cardiac muscle is to rhythmically contract and relax throughout life without fatigue and to pump the blood and distribute it to the various parts of the body. |
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| Nature, Occurrence and Function |
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| Neuron |
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| The brain, spinal cord and nerves are all composed of nervous tissue. Each nerve cell is called a neuron. These are highly specialized cells. They have the ability to receive stimulus from within or outside and send impulses to different parts of the body. Each cell consists of three parts, the cyton or the cell body, the dendrons which are short processes arising from the cyton and further branch into thin dendrites and the axon which is a single long cylindrical process forming fine branches terminally. Dendrites receive impulses and the axon takes impulses away from the cell body. |
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Tissues in Plants and Animals
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