. Biophysics: concepts and mechanisms. Biophysics. 284 BIOPHYSICAL STUDIES ON NERVE AND MUSCLE tissue, as revealed by the light and electron microscopes, and a bit about the chemistry of muscle proteins, to see where myosin fits in. Structure of Muscle Tissue Figure 10-12 illustrates what is seen by means of higher- and higher- resolution microscopic examination of muscle. A muscle is made up of fibers, which appear striated under the light microscope. Phase contrast and interference attachments reveal that a fiber is composed of myofibrils, along the side of which lie mitochondria and nuclei
. Biophysics: concepts and mechanisms. Biophysics. 284 BIOPHYSICAL STUDIES ON NERVE AND MUSCLE tissue, as revealed by the light and electron microscopes, and a bit about the chemistry of muscle proteins, to see where myosin fits in. Structure of Muscle Tissue Figure 10-12 illustrates what is seen by means of higher- and higher- resolution microscopic examination of muscle. A muscle is made up of fibers, which appear striated under the light microscope. Phase contrast and interference attachments reveal that a fiber is composed of myofibrils, along the side of which lie mitochondria and nuclei (not shown). The electron microscope reveals that a myofibril appears segmented because of a repeat- ing pattern of light and dark bands throughout. Repeating patterns, bounded by the end- or "Z"-lines contain a faint "M"-line in the middle, bounded first by narrow H-zones and then the wider "A"- (for anisotropic) bands which span the middle. Isotropic 'T'-bands span the "Z"-lines (see Figure 10-12). fibres Tendon Uh i i r (a) Whole Muscle (â vl cm.) Muscle Fibre i 50-100/j) mmm) z z z z 1 ' sarcomeres Myofibril (1-2 u) â Iâ. (actin) Figure 10-12. Schematic Drawings of Muscle Under Higher and Higher Reso- lution Microscopy, (a) Light microscope; (b) Electron microscope. During shortening the horizontal thick and thin filaments slide farther into each other, so that only the H and / bands shorten. Under great magnification (~300,000 x ) a rather comical contraption is disclosed: an array of overlapping thick and thin filaments, which run paral- lel to the myofibril, and which apparently slide back and forth over each other as the muscle contracts and relaxes. Partial overlap of the thick and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Casey, Edmund Jeremiah, 192
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