Review Sheet Skeletal Muscles

REVIEW SHEET EXERCISE 2 Skeletal Muscle Physiology NAME: Jasmine Young LAB TIME/DATE: 1. Define each of the following terms: • motor unit - A motor unit consists of a motor neuron and all of the muscle fibers it innervates. • twitch - Skeletal Muscle twitch is the mechanical response to a single action potential. It has three phases known as the latent, contraction, and relaxation phase. • threshold - the threshold is the minimal stimulus needed to cause a depolarization of the muscle plasma membrane (sarcolemma.) The threshold is the point at which sodium ions start to move into the cell (instead of out of the cell) to bring about the membrane depolarization. • treppe - the progressive increase in force generated when a muscle is stimulated at a sufficiently high frequency • summation - When a muscle is stimulated repeatedly, such that the stimuli arrive one after another within a short period of time, twitches can overlap with each other and result in a stronger muscle contraction than a stand-alone twitch • tetanus - if stimuli continue to be applied frequently to a muscle over a prolonged period of time, the muscle force will eventually reach a plateau • fatigue - a decline in a muscle’s ability to maintain a constant force of contraction after prolonged, repetitive stimulation. • isometric contraction - When a muscle attempts to move a load that is greater than the force generated by the muscle • isotonic contraction - When a muscle attempts to move a load that is equal to or less than the force generated by the muscle

2. Describe the process of excitation-contraction coupling. An AP in a motor neuron triggers the release of Ach. Ach diffuses into the sarcolemma & binds to receptors in the muscle cell. The resulting change in ion permeability triggers a depolarization of the plasma membrane called an end plate potential. The end plate potential triggers a series of events that results in the contraction of a muscle cell.

3. What is the role of