. Biophysics: concepts and mechanisms. Biophysics. 272 BIOPHYSICAL STUDIES ON NERVE AND MUSCLE. Figure 10-5. Electron Micrograph of an Ultrathin Section of Nerve Axon which is Myelin- ated by the Spiral Wrap of the Double-Membraned Schwann Cell. Magnification 90,000 x . (Courtesy of J. D. Robertson, Harvard Medical School, and of Scientific American.) ure 10-1) the impulse is forced to skip from node to node, perhaps via semi- conductivity, although it may be by proton transfer ("protochemical" cells have been demonstrated in the laboratory) through the myelin. In any case the skippi
. Biophysics: concepts and mechanisms. Biophysics. 272 BIOPHYSICAL STUDIES ON NERVE AND MUSCLE. Figure 10-5. Electron Micrograph of an Ultrathin Section of Nerve Axon which is Myelin- ated by the Spiral Wrap of the Double-Membraned Schwann Cell. Magnification 90,000 x . (Courtesy of J. D. Robertson, Harvard Medical School, and of Scientific American.) ure 10-1) the impulse is forced to skip from node to node, perhaps via semi- conductivity, although it may be by proton transfer ("protochemical" cells have been demonstrated in the laboratory) through the myelin. In any case the skipping mechanism is very fast, and therefore a sheathed nerve nor- mally conducts an impulse somewhat faster than an unsheathed one. The Trigger To fire the nerve and incite the transmission of an impulse, a stimulus is required. Stimuli are essentially of five kinds: (1) Electrical: voltage changes applied directly to the cells of the nerve— in the brain for example. (2) Mechanical: pressure changes causing distortion at nerve endings— ear, and mechanoreceptors associated with the sense of touch. (3) Electromagnetic: incident radiation absorbed by pigment molecules in cells sensitive to visible light, and by other transducer molecules sensitive to warming (infrared) radiations—eye, and a multitide of closely spaced detectors all over the body's 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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