Enter your Name:   Enter your E-mail Address:  Define the following terms: 01a. Sarcomere 01b. Motor unit 01c. All-or-none law of skeletal muscle contraction 01d. Muscle tone 02. Muscle tissue is striated when examined under a microscope. What kind of muscle tissue is this? 03. Label the following structures of a muscle: 04. Label the parts of the sarcomere below: 05. Using the figure above, indicate which things remain the same when a sarcomere contracts. a. The length of the structure labeled (a) in the figure b. The length of the structure labeled (b) in the figure c. The length of the structure labeled (c) in the figure d. The length of the structure labeled (d) in the figure e. The distance between the Z disks 06. Fill in the blanks Without _______________ to destroy ________________, a muscle cell would stay contracted. 07. How does the membrane action potential get to the sarcoplasmic reticulum? 08. Calcium ions are diffusing across the membrane of the sarcoplasmic reticulum. Is the cell beginning contraction or ending contraction? 09. When a sarcomere contracts, what happens between the power stroke and the return stroke? 10. What must happen after the action potential reaches the presynaptic terminal and before an action potential is established on the membrane of a muscle cell? 11. Two muscle fibers lie side-by-side but contract at different times. Are they a part of the same motor unit? 12. Fill in the blank: If a muscle is stiff, there is not enough _______________ in the muscle cells. 13. A nerve is being stimulated with a submaximal stimulus. Are there any motor units that have been recruited? 14. A motor unit is recruited. What happens to the muscle fibers in that motor unit? 15. Lactic acid is building up in a muscle cell. What kind of respiration is occurring? 16. A muscle cell is using creatine phosphate to convert ADP into ATP. Does this require oxygen?