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Control of Muscle Contraction

Control of Muscle Contraction - Actin and myosin whose...

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Control of Muscle Contraction Neuromuscular junctions are the point where a motor neuron attaches to a muscle. Acetylcholine is released from the axon end of the nerve cell when a nerve impulse reaches the junction. A wave of electrical changes are produced in the muscle cell when the acetylcholine binds to receptors on its surface. Calcium is released from its storage area in the cell's endoplasmic reticulum . An impulse from a nerve cell causes calcium release and brings about a single, short muscle contraction called a twitch. Skeletal muscles are organized into hundreds of motor units , each of which is a motor neuron and a group of muscle fibers. A graded response to a circumstance will involve controlling the number of motor units. While individual muscle units contract as a unit, the entire muscle can contract on a graded basis due to their organization into motor units. Contraction of Nonmuscular Cells
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Unformatted text preview: Actin and myosin, whose interaction causes muscle contraction, occur in many other cells. Actin is attached to the inner surface of the plasma membrane. The interaction of cytoplasmic myosin and this actin causes contraction of the cell, such a the coordinated contractions of intestinal cells to absorb nutrients. Some fish have modified muscles that discharge electricity. These fish have electric organs consisting of modified muscles known as electroplates. The South American electric eel has more than 6000 plates arranged into 70 columns. Maximum discharge is 100 watts. Interaction of the Two Systems Vertebrates move by application of the principles of the lever. Levers amplify or increase the force or velocity of motion. The amount of amplification depends on the length of the lever. There are three types of skeletal system, all interact with muscles using the lever....
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