Thursday, November 11, 2010
Nervous and Muscle tissue
Thursday, November 11, 2010 by Faizan Bhatti
It is composed of several different types of cells but two are important named Neuron and neuroglia. Neurons are impulse conducting cells and consist of three parts, dendrites, cell body and axon. Dendrite receives nerve impulses and pass on to the cell body. The cell body is thickest area that contains muscles and other cell organelles of the cell. Axon is long thread like extension of cell body which conducts nerve impulse away from the cell body. In some peripheral nerves, the axon is enclosed by Schwann cells that act as insulating material. Neurons are specialized to transmit signals called nerve impulses from one neuron to the other, from sense organs to the brain, from brain to effectors that is the muscles and glands. Neuroglia is non nervous cell that insulates the membranes of neurons, provides protection support and nourishment to the neurons. Nervous tissue is located in brain, spinal cord and nerves.
Muscle tissues are composed of long, excitable cells capable of considerable contraction. In the cytoplasm of muscle cells are present large number of parallel arranged structures called microfilaments that are made up of contractile proteins actin and myosin. Muscle is the most abundant tissue in animals and the contraction of muscle accounts for much of the energy consuming cellular working in an active animal. There are three types of tissues called Smooth muscle, skeletal muscle and Cardiac muscle.
(1) Smooth Muscle Tissue:
Smooth muscles lack cross striations and are spindle shaped containing single nucleus. These are involuntary in action and are thus named as involuntary muscles. The contract slowly than the skeletal muscles but for longer periods of time than skeletal muscles. These cells are arranged closely to form sheets and are mostly located in the walls of hollow organs like gut, blood vessels, and ducts of reproductive and excretory systems. It helps in the movement of substances like food, urine.
(2) Skeletal Muscle Tissue:
Skeletal fibre is composed of striated muscle fibres that are long, cylindrical and contains many peripheral nuclei. They are voluntary in nature and are attached with bones by tendons. The contraction helps in the bone to move and hence it helps in locomotion of animal.
(3) Cardiac Muscle Tissue:
It consists of striated branched spindle shaped cells that are shorter than the skeletal cells. Each cell contains single nucleus and specialized cell junctions called inter calated dises that allow ions to move quickly from one cell to the other. These are located in wall of the heart and it has involuntary control. As the walls of the heart contract cardiac muscle tissue pumps blood into circulation. Tags: Biology , Zoology
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