Skeletal Muscle [antikvár]

PrefaceScanning the history of science, we see how keen has been the animus to investigate the structure of contractile elements in the hope of discovering the secret mechanism of the most important phenomenon of animal lifemovement!Studies on muscle tissue by anatomists and physiologists throughout the years number in the hundreds. These studies have been conducted with diverse methodseach more perfect than the last, as technology became enriched with instruments, more precise methods of observation and measurement, and new contrivances capable of revealing the most minute structural detailsand conducted with diverse objectives, as general notions on animal organization were modified. These studies represent many generations' steadfast pursuit of the solution to a great problem in biology.And still we are far from reaching the goal.EmUio Veratti, 1902 (transl. 1959; see chapt. 2 for refs.)The Handbook of Physiology: Skeletal Muscle appears eight decades after Veratti wrote the above, yet the enthusiasm for contractile systems that he felt seems undiminished in the authors of this volume. Furthermore the goal of a full understanding of the workings of a muscle cell does not seem any closer to us than it did to Veratti. This is the nature of scientific investigation; each time we piece together some answers, we uncover new questions, and all the while we advance. In the last 25 years we have seen unprecedented growth in our knowledge of biological structure and function at the cellular and subcellular level. Clearly these advances have depended on high levels of scientific interest and adequate funding for research. At least equally important has been the availability of powerful new microscopic, mechanical, electronic, and chemical techniques. I think Veratti, were he alive today, would have enjoyed immensely seeing the networks he so elegantly described in muscle cells as we now see them in the high-voltage electron microscope. During his lifetime Veratti's ideas were not as widely accepted as they are now. To be fair, however, in 1902 it would have been difficult to know how real his observations were, without the information we now have. Each era has its mysteries, its limited tools for investigating them, its failures, and its successes. Oftenonly in retrospect can we teU the successes from the failures. Thus we must continually review the state of our knowledge, look back at past results, and plan future experiments. These are the goals of this book.During the last 25 years, muscle tissue has been probed as deeply and studied as thoroughly vrith many modern techniques as any other tissue. Two reasons for this are the large size of muscle cells and their high degree of functional and structural specialization, which make them particularly well suited for study with the newer biophysical and biochemical instruments and techniques. The organization of a striated muscle ceU in repeating structural units (fibrils and sarcomeres) allows microscopists to concentrate on these small units in detail, looking at the whole fiber as an assembly of many such parts. The repeating structural pattern allows diffractionists to join in as well, and both X-ray-diffraction and light-diffraction techniques are contributing to our present knowledge of muscle structure and function.When muscle ceUs are activated, they produce mechanical signals of considerable amplitude, thus permitting studies of the contractUe system itself. Muscle ceUs also produce electrical signals with large amph-tudes, often more than 0.1 V in total excursion, and with time scales easily recorded by modern electronic instruments. These signals are expressions of the activities of membranes that control the contractUe state of the cell, and detailed understanding of them is needed before we can fuUy understand how a muscle cell works. Finally, because of the high degree of specialization of muscle ceUs, the common contractile proteins are present in such abundance in the ceU that simple extraction gives an already rather well-purified product for biochemical studies.Thus it is not surprising that biophysicists, physiologists, biochemists, and anatomists have been attracted in such large numbers to the study of skeletal muscle and that they have had such remarkable success. Many questions that excited Veratti and his colleagues at the turn of the centm-y have been answered and replaced with new questions, which a new generation with new techniques is trying to answer. There is much to keep the animus, and the anima, keen.The central purpose of Skeletal Muscle, like that of