Skeletal Muscle Physiology
1. Skeletal muscle fiber- long, cylindrical cell with multiple oval nuclei arranged just beneath the sarcolemma Motor unit- all of the muscle cells controlled by a single motor neuron Skeletal muscle twitch- a single stimulus-contraction-relaxation cycle in a skeletal muscle Electrical stimulus- uses an electrical current to cause a single muscle or a group of muscles to contract Latent period- the time between the stimulation of a muscle and the start of the contraction phase 2. Acetylcholine is the chemical signal the nerve sends to the muscle to cause contraction. 3. The motor unit meets at the neuromuscular junction, where the axon terminal of a neuron and muscle fiber's plasma membrane meet, also called the motor end plate. What occurs in this area leads to the end-plate potential, where an action potential in motor neurons causes the release of acetylcholine. The acetylcholine diffuses into the muscle fiber membrane and changes the ions permeability that creates graded depolarization of the end-plate potential. The end-plate potential triggers events that create contraction of the muscle cell. 4. During the latent phase there is no muscle contraction. This phase is the period of time prior to muscle contractions, however chemical changes in the cells occur in preparation for muscle contractions. The contraction phase is the period in which the muscle tension is at its highest. This is the time where the greatest amount of muscle force is generated. It begins at the end of the latent period and ends when tension peaks. The relaxation phase is the period of contraction after the contraction phase, and ends at the end of muscle contraction. 5. No. In all tests, the latent period remained the same, at 2.80 msec. This was what I had predicted. 6. The sodium ions start move into the cell to bring about the membrane depolarization. Activity 2
1. As the stimulus voltage is increased past the muscle's...
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