. Biophysics: concepts and mechanisms. Biophysics. 264 BIOPHYSICAL STUDIES ON NERVE AND MUSCLE. string Figure 10-1. Nerve Cell and Axons. The length of the axon is sometimes as much as 100,000 times the length of the cell. Insertion of Micropipets and Micro- electrodes. Stimulating (or detecting) electrodes touching myelin sheath. optical and electron-microscopic methods made it all the more attractive as a subject for study. In the next section some of the pertinent information which has been ob- tained from the lowly squid is summarized. This information has formed the basis of a better unde
. Biophysics: concepts and mechanisms. Biophysics. 264 BIOPHYSICAL STUDIES ON NERVE AND MUSCLE. string Figure 10-1. Nerve Cell and Axons. The length of the axon is sometimes as much as 100,000 times the length of the cell. Insertion of Micropipets and Micro- electrodes. Stimulating (or detecting) electrodes touching myelin sheath. optical and electron-microscopic methods made it all the more attractive as a subject for study. In the next section some of the pertinent information which has been ob- tained from the lowly squid is summarized. This information has formed the basis of a better understanding of the biophysics of nerve conduction. Nerve is similar enough from one species to another that some generalities can be assumed on the basis of information gained from the squid axon. The Era of the Squid Curtis and Cole by 1936 had placed metal electrodes inside and out- side the squid's tube-shaped axon; and with a conventional Wheatstone bridge, had made measurements of the electrical resistance (20,000 ohms/cm2) and electrical capacitance (1 microfarad (^f) per cm2) of the membrane. Further, they showed that the resistance is much lower when the nerve is actively transmitting impulses. With the development of electronic dc amplifiers and oscilloscopes, it became possible to display the passage of the nerve impulse as detected by thin platinum-wire contacts (electrodes) touching the nerve (see bottom of Figure 10-1, for example). The impulse turned out to be a band of negative charge passing down the outside surface of the axon, from the point of stimulation to the far end. The insert in Figure 10-2 shows the electrical. 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, 1924-. New York, Reinhold Pub. Corp
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