2. Sarcomere Sarcolemma Sarcoplasmic Reticulum A similar picture can be found on page 169 of the reading packet, figure 8.4. * Note that the sarcoplasmic reticulum “surrounds” each myofibril. * Also note that the sarcoplasmic reticulum seems to form repeating units that “surround” individual sarcomeres . Z-line Z-line

4. sarcomere Myofibril * Note that a sarcomere is a repeating unit of contraction within the myofibril. * The myofibril can be seen to be made up of repeating units of overlapping myofilaments .

7. Skeletal Muscle Fiber (Myocyte) sarcoplasmic reticulum (the “blue” tubes) T-tubules (the “purple” tubes) Myofibril A similar picture can be found on page 169 of the reading packet, figure 8.4. Sarcolemma

10. Axon branch of motor neuron Motor End Plate Neuromuscular Junction