Lab Report 1 - Skeletal Nerve-Muscle Association George...

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Skeletal Nerve-Muscle Association George Gavrilos, David Kim, Sonali Vakharia, Jason Wang Introduction Throughout the course of history, scientists, pharmacologists, and physiologists have studied the physiological phenomenon called muscle contraction. Beginning with the mid-1700s, many advances have been made which have ultimately led us to a greater understanding of this important physiological function. Between the years of 1780 and 1794, Italian physician and physicist, Dr. L. Galvani, was the first to use frogs in order to show that muscles contract when stimulated by electricity. A few centuries later, in 1921, Dr. O. Loewi, a German physician and pharmacologist, proved that acetylcholine is involved in transmitting impulses from one nerve cell to another and from the nerve cell to the muscle. From 1939 to 1946, biochemist A. Szent-Gyorgyi discovered the actin and myosin myofilaments, and proposed that ATP was necessary as the energy source for muscle contraction. In 1969, one of the most important theories in muscle contraction physiology was proposed by molecular biologist H.E. Huxley and physiologist A.F. Huxley, the sliding-filament theory ( Larach, ?) . Since then, physiologists have a clearer understanding of how a nerve impulse influences the contraction of a skeletal muscle. An action potential travels down a motor neuron to the axon terminal where it causes the secretion of acetylcholine, an excitatory neurotransmitter substance utilized in neuromuscular junctions. After being secreted into the synapse, acetylcholine binds to ligand-gated sodium channels located on the motor endplate of the skeletal muscle’s plasma membrane – the sarcolemma. The binding of acetylcholine opens these channels, allowing large amounts of sodium to diffuse internally into the cell, and through local current flow, opens voltage gated channels which ultimately cause depolarization and an action potential.
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