M14_MARI0000_00_SE_CH14.qxd 3/28/11 2:59 PM Page 84 REVIEW SHEET NAME ____________________________________ EXERCISE 14 LAB TIME/DATE _______________________ Microscopic Anatomy and Organization of Skeletal Muscle Skeletal Muscle Cells and Their Packaging into Muscles 1. Use the items in the key to correctly identify the structures described below. Key: g; perimysium 1. connective tissue ensheathing a bundle of muscle cells a. endomysium c; fascicle 2. bundle of muscle cells b. epimysium c. fascicle i; sarcomere 3. contractile unit of muscle d. fiber d; fiber 4. a muscle cell e. myofibril a; endomysium 5. thin reticular connective tissue surrounding each muscle cell f. myofilament h; sarcolemma 6. plasma membrane of the muscle fiber g. perimysium e; myofibril 7. a long filamentous organelle with a banded appearance found h. sarcolemma within muscle cells i. sarcomere f; myofilament 8. actin- or myosin-containing structure j. sarcoplasm k; tendon 9. cord of collagen fibers that attaches a muscle to a bone k. tendon 2. List three reasons why the connective tissue wrappings of skeletal muscle are important. The connective tissue wrappings (a) bundle the muscle fibers together, increasing coordination of their activity; (b) add strength to the muscle; and (c) provide a route for entry and exit of blood vessels and nerves to the muscle fibers. 3. Why are there more indirect—that is, tendinous—muscle attachments to bone than there are direct attachments? They conserve space (less bulky than fleshy muscle attachments) and are more durable than muscle tissue where bony prominences must be spanned. 4. How does an aponeurosis differ from a tendon structurally? An aponeurosis is a sheet of white fibrous connective tissue; a tendon is a band or cord of the same tissue. How is an aponeurosis functionally similar to a tendon? Both serve to attach muscles to bones or to other muscles. 84 Copyright © 2011 Pearson Education, Inc. M14_MARI0000_00_SE_CH14.qxd 3/28/11 2:59 PM Page 85 5. The diagram illustrates a small portion of several myofibrils. Using letters from the key, correctly identify each structure indicated by a leader line or a bracket. Key: a. A band d. myosin filament g. triad b. actin filament e. T tubule h. sarcomere c. I band f. terminal cisterna i. Z disc h a c d b i g f e 6. On the following figure, label a blood vessel, endomysium, epimysium, a fascicle, a muscle cell, perimysium, and the tendon. Perimysium Blood vessel Endomysium Muscle cell (fiber) Tendon Epimysium Fascicle Review Sheet 14 85 Copyright © 2011 Pearson Education, Inc. M14_MARI0000_00_SE_CH14.qxd 3/28/11 2:59 PM Page 86 The Neuromuscular Junction 7. Complete the following statements: The junction between a motor neuron’s axon terminal and the muscle cell 1. ________________________neuromuscular (myoneural) membrane is called a(n) __1__ junction. A motor neuron and all of the skeletal muscle cells it stimulates is called a(n) __2__. The actual gap between the axon 2. ________________________motor unit terminal and the muscle cell is called a(n) __3__. Within the axon terminal are many small vesicles containing a neurotransmitter substance called__4__. When 3. ________________________synaptic cleft the __5__ reaches the ends of the axon, the neurotransmitter is released and dif- fuses to the muscle cell membrane to combine with receptors there. The combining 4. ________________________acetylcholine of the neurotransmitter with the muscle membrane receptors causes the membrane to become permeable to both sodium and potassium. The greater influx of sodium ions results in __6__ of the membrane. Then contraction of the muscle cell occurs. 5. ________________________action potential (nerve impulse) 6. ________________________depolarization 8. The events that occur at a neuromuscular junction are depicted below. Identify by labeling every structure provided with a leader line. Key: d a. axon terminal Action potential b. mitochondrion c. muscle fiber a d. myelinated axon e. sarcolemma Nucleus f. synaptic cleft c g. T tubule h. vesicle containing ACh h b f Junctional folds of the sarcolemma g Part of a myofibril 86 Review Sheet 14 Copyright © 2011 Pearson Education, Inc..