Noway For Science Essay

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Brain is the part of the nervous system that is enclosed in the skull . All vertebrates (animals with backbones ) have well-developed brains most invertebrates (animals without backbones ) do not have true brains . Instead , they have groups of nerve cells called nerve nets , nerve cords , or ganglia . This article is concerned almost entirely with the human brain . The human brain is an extension of the spinal cord , and with it makes u the central nervous system . It contains billions of neurons , or nerve cells , each with more than 10 ,000 synapses , or connections to other neurons . No two brain cells but it can bypass dead or damaged cells to form new synapses between existing cells (Corrick , 2003 . The brain receives information from all parts of the body and sends out instructions to the body 's various organs and systems . The information and instructions travel through the brain in the form of nerve impulses , electrical signals that elicit chemical changes . The impulses travel along the neurons and move from one neuron to the next across the synapses by means of chemicals called neurotransmitters . It is through nerve impulses that the brain controls such activities as voluntary and involuntary movement . The brain is connected with the sense organs , muscles of the head , and internal organs of the body by 12 pairs of cranial nerves , carry impulses from the brain to various parts of the body . Others , called sensory nerves , carry impulses from the body back to the brain . Most pairs of cranial nerves contain one motor and one sensory nerve a few pairs contain sensory nerves only . The brain consists of two types of tissue (1 ) nerve cells , or gray matter and (2 ) sheathed nerve fibers , or white matter . The sheath is composed of myelin , a fatty protein that protects and insulates the fibers (Kolb ,

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