Anatomy & Physiology

Anatomy & Physiology Study Guide

4.4 Neural Tissue Neural tissue, also known as nervous tissue or nerve tissue, is specialized for the conduction of electrical impulses from one region of the body to another. Ninety-eight percent of the neural tissue in the body is concentrated in the brain and spinal cord (the control centers of the nervous system).

Neural tissue contains two basic types of cells: neurons and neuroglia, or glial cells used for support. Our conscious and unconscious thought processes reflect the communication among neurons in the brain. Such communication involves the transmission of electrical impulses. Information is conveyed both by the frequency and by the pattern of the impulses. Neuroglia support and repair neural tissue and supply nutrients to neurons. Most neurons cannot divide under normal circumstances; thus, they have a limited ability to repair themselves after injury. A typical neuron has a large cell body with a large nucleus. Extending from the cell body are many branching processes called dendrites and an axon. The dendrites receive information from other neurons, and the axon conducts information to other cells. 4.5 Tissue Repair The response to tissue injury involves inflammation and regeneration. Immediately after an injury, the area is isolated while damaged cells, tissue components, and any dangerous microorganisms are cleaned up. This process coordinates the activities of several types of tissue and is called inflammation , or the inflammatory response. It produces signs and symptoms of injury, including swelling, redness, warmth, and pain. Inflammation may also result from the presence of pathogens, such as harmful bacteria within the tissues. The presence of these pathogens constitutes an infection. Second, the damaged tissues are replaced or repaired to restore normal function. The repair process is called regeneration . By the time the inflammation phase is over, the situation is under control, and no further damage will occur. However, many cells in the area either have already died or will soon die as a consequence of the original injury. As tissue conditions return to normal, fibrocytes move into the necrotic area and lay down a network of collagen fibers that stabilize the injury site. This process produces a dense, collagenous framework known as scar tissue or fibrous tissue. Over time,

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