Muscle Contraction The Cross Bridge Cycle

Muscle Lab 2 Muscle Twitch & Latent Period 1. Which of the following terms are NOT used interchangeably? a. in vivo - in the body/ the living b. muscle tension - muscle force c. muscle cell - muscle fiber d. motor unit - motor neuron 2. Which of the following is NOT a phase of a muscle twitch? a. latent period b. relaxation phase c. contraction phase d. shortening phase 3. Where does the acetylcholine that stimulates muscle contraction bind? a. receptors in the sarcoplasmic reticulum b. receptors in troponin c. receptors in the axon terminal receptors d. receptors in the motor end plate 4. When acetylcholine binds to its receptors, it results in __________. a. the end plate potential b. a graded depolarization c. a change in ion permeability d. the end plate potential, a graded depolarization, and a change in ion permeability 5. Which of the following occurs during the latent period of muscle contraction? a. An action potential is generated. b. Acetylcholine is released at the axon terminal and an action potential is generated. c. Acetylcholine is released at the axon terminal. d. Calcium is released from the sarcoplasmic reticulum. 6. As the stimulus voltage was increased in this activity, which of the following occurred? a. he latent period increased in length. b. The muscle force generated increased. c. The latent period decreased in length. d. The muscle force generated decreased. 7. Which of the following describes the relaxation phase? a. The sarcomeres are increasing in length, and the force generated decreases. b. The sarcomeres are decreasing in length, and the force generated decreases. c. The sarcomeres are decreasing in length, and the force generated increases. d. The sarcomeres are increasing in length, and the force generated increases. 8. Which of the following can trigger a muscle twitch? a. release of acetylcholine or electrical stimulation b. release of acetylcholine c. electrical stimulation d. release of calcium from the sarcolemma e. release of acetylcholine or release of calcium from the sarcolemma Effect of Stimulus Frequency on Skeletal Muscle Contraction 1. Treppe is the phenomenon that results in _______. a. motor unit recruitment b. maximal force production by a skeletal muscle c. a progressive increase in the force generated with repetitive stimulation d. an increase in the stimulation frequency 2. When the frequency of stimulation of a muscle is great enough, _______. a. full relaxation of the muscle occurs and wave summation results b. full relaxation of the muscle occurs c. muscle twitches overlap d. wave summation results e. wave summation results and muscle twitches overlap. 3. When wave summation occurs, _______. a. the muscle force generated decreases b. individual muscle twitches are separated c. the muscle force generated increases d. the muscle fiber has received a single stimulus event 4. Why does wave summation occur? a. Muscle fibers are partially contracted when the next stimulus arrives. b. A large amount of time elapses between stimulations. c. Muscle fibers have been allowed to fully relax. d. Muscle twitches are not yet overlapping. 5. Which of the following produced an increase in stimulus intensity? a. increasing the voltage applied b. clicking the mouse in rapid succession c. allowing the muscle to completely relax in between contractions d. clicking the mouse in rapid succession and allowing the muscle to completely relax in between contractions 6. Which of the following produced an increase in stimulus frequency? a. clicking the mouse in rapid succession and allowing the muscle to completely relax in between contractions b. allowing the muscle to completely relax between contractions c. clicking the mouse in rapid succession d. increasing the voltage applied 7. Which of the following does NOT describe treppe? a. A period of relaxation can be seen on the muscle twitch tracing. b. An incremental increase in force occurs. c. An increase in stimulus intensity is required to see the effect. d. It is also referred to as the “staircase” effect. TREPPE COMES TO REST, WAVE SUMMATION = RAPID STIMULATION, no full rest in between Fatigue in Isolated Skeletal Muscle 8. Which of the following is matched correctly? a. complete tetanus - unfused tetanus b. incomplete tetanus - fused tetanus c. incomplete tetanus - fatigue d. complete tetanus - fused tetanus 9. Which of the following situations delay the development of muscle fatigue the longest? a. Prolonged muscle contraction b. Repetitive stimulation of a muscle c. Alternating sprints with up-hill jogging d. Consistent interruptions of muscle stimulation e. High intensity exercise 10. Which of the following molecules is NOT thought to accumulate during muscle fatigue? a. ADP b. ATP c. inorganic phosphate d. lactic acid 11. During muscle fatigue, the ____________ decreases. a. stimulus frequency b. number of muscle fibers c. rest period d. force of contraction 12. In this activity, why did the muscle force decrease over time? a. Intracellular calcium built up. b. The stimulation frequency was increased. c. Muscle fatigue developed. d. The stimulation frequency was decreased. 13. Which of the following describes how increasing the duration of the rest period affected muscle tension? a. Increasing the duration of the rest period had no effect on the subsequent maximal tension. b. Increasing the duration of the rest period decreased the duration of subsequent maximal tension. c. Increasing the duration of the rest period increased the duration of the subsequent maximal tension. d. Increasing the duration of the rest period decreased the amount of the subsequent maximal tension. 14. What might be occurring on a molecular level during the rest periods? a. Muscle fatigue is increasing. b. Intracellular lactic acid is increasing. c. Intracellular ADP and inorganic phosphate are decreasing. d. Intracellular calcium is decreasing. Isotonic contractions and the Load-Velocity Relationship 1. Which of the following occurs during isotonic concentric contraction? a. The length of the muscle decreases with contraction. b. The length of the muscle increases with contraction. c. The length of the muscle increases and decreases with contraction. d. The length of the muscle stays the same. 2. Which of the following occurs during the latent period of isotonic concentric contraction? a. Muscle tension is not produced, and the weight will not move. b. Muscle tension is not produced, and the weight will move. c. Muscle tension is produced, and the weight will not move. d. Muscle tension is produced, and the weight will move. 3. The speed of muscle contraction is called the _______. a. isometric velocity b. shortening velocity c. twitch velocity d. contraction velocity 4. For a weight to be lifted, which of the following must occur? a. An isometric muscle contraction with a force less than the load. b. An isotonic muscle contraction with a force greater than the load. c. An isotonic muscle contraction with a force less than the load. d. An isometric muscle contraction with a force greater than the load 1. Does the highlighted muscle flex the neck to the same side or to the opposite side? Same Side 2. How many total pairs of the highlighted muscle does each individual have? 11 They are external intercostals muscles 3. Name one bone on which the highlighted muscle originates. sternum or clavicle The muscle = sternocleidomastoid 4. Cardiac muscle cell 5. Intercalated discs 6. Perimysium 7. Smooth muscle fiber 8. striations