Neuromuscular Diseases - The Motor Unit, Causes Of Neuromuscular Dysfunction, Muscular Dystrophy, The Neuromyopathies, Progressive Muscular Atrophy - The neuropathies: symptoms and clinical findings
nerves disorders muscles system
When humans are in good health, the nervous system and musculature work together so smoothly there is little awareness of how efficiently this complicated biochemical machine functions. Neuromuscular diseases include a vast and bewildering array of related and unrelated disorders that have a certain similarity of symptoms in that both nerves and muscles are usually impaired. This term is usually applied to disorders of the motor unit and specifically excludes primary disorders of the central nervous system such as cerebral palsy.
Various types of diseases involve both the nerves and muscles. Some pathologic processes destroy nerves; others primarily attack muscles. Although the cause (or causes) of practically all of them still remain unknown, all are under intensive study.
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The motor unit has four components: a motor neuron in the brain or spinal cord, its axon and related axons that comprise the peripheral nerve, the neuromuscular junction, and all the muscle fibers activated by the neuron. Like other cells, nerve and muscle cells have an external membrane that separates the inner fluids from those on the outside. The fluid on the inside is rich in potassium (K), ma…
When a single nerve impulse strikes a muscle it causes a "twitch," and ordinarily there is a brief refractory period of relaxation. If another impulse is received before relaxation is completed, the twitches can add up and cause a prolonged muscular spasm or tetany. Normally, muscles continue to function properly because the ACh transmitted down the nerve is enzymatically eliminated.…
This primary degenerative process, first described by Wilhelm Erb in 1891, affects the muscular fibers, not the nerves or end plates. In spite of extensive research, the cause has not yet been firmly established, although genetic factors are receiving strong consideration. A variety of types and classifications have been proposed, but all are based on age of onset, symptomatology, and rate of prog…
Neuromyopathies are similar to the dystrophies in that there is both nerve and muscular involvement, but there are also differences between the two categories. Some neuromyopathies start in childhood, while others begin later in life. Neuromyopathies involve more brain and spinal cord damage; causes can include infectious diseases, allergic conditions, immunologic problems, and toxic or traumatic …
Although there are several variations of this disorder, they all show wasting of the muscles ("atrophy") secondary to degeneration of the motor nerve system. The most common type is called amyotrophic lateral sclerosis and is popularly known as Lou Gehrig disease. Onset generally occurs between ages 40-70, but the disease can begin at other times in life. Although it may begin on one…
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