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BIOL 220 Human Anatomy & Physiology L Final Exam December 12, 2007 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the period during which the events of excitation-contraction coupling occur. A) contraction B) refractory C) latent 1D) relaxation 2) Nervous stimulation of the muscle cell opens: A) voltage gated sodium channels. B) chemically gated sodium/potassium channels C) voltage gated calcium channels. D) chemically gated potassium channels. 3) After nervous stimulation of the muscle cell has ceased, the caleium: A) is actively pumped into the sarcoplasmic reticulum for storage until the next contraction. B) is destroyed by cholinesterase. C) level in the cytoplasm increases. D) is chemically bound to the filaments. 4) In an isotonic contraction, the muscle: A) does not change in length but increases tension. B) is usually unable to move the load. C) changes in length and moves the “load.” D) always has to shorten. 5) Theoretically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped: A) cross bridge attachment would be optimum because of all the free binding sites on actin. B) ATP consumption would increase since the sarcomere is "trying" to contract. C) maximum force production would result since the muscle has a maximum range of travel. D) no muscle tension could be generated. 6) Some snake venoms contain molecules that bind irreversibly to the ACh receptors on the sarcolemma, The venom molecules thus block ACh from binding to their receptors. Ignoring the effects on any other system, the consequence to skeletal muscle would be: A) irreversible contraction as soon as the first nervous stimulation reached the sarcolemma. B) continuous musle contraction and relaxation. C) no contraction at all by nervous mechanisms. D) calcium release from the muscle cell. 2) 3) 4) 6)