. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 780 Comparative Animal Physiology of msec). The negative after-potential is increased by veratrine, by the alkahne earths, and by tetanization of a nerve trunk. In crab nerve fibers the negative after-potential persists for 15 minutes or more.^-'^^- -^^ The after- negativity in crab fibers, as in vertebrate fibers, is prolonged by veratrine^" and by repetitive stimulation.'^° (5) A positive after-potential follovi's the negative after-potential (Fig. 293, A). It may persist for 100 msec, in small mammaf
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 780 Comparative Animal Physiology of msec). The negative after-potential is increased by veratrine, by the alkahne earths, and by tetanization of a nerve trunk. In crab nerve fibers the negative after-potential persists for 15 minutes or more.^-'^^- -^^ The after- negativity in crab fibers, as in vertebrate fibers, is prolonged by veratrine^" and by repetitive stimulation.'^° (5) A positive after-potential follovi's the negative after-potential (Fig. 293, A). It may persist for 100 msec, in small mammafian fibers and for several seconds in frog fibers. It may last for many minutes in crab fibers.*^^'' After-positivity is enhanced by yohimbine, by low calcium, and by a tetanus. A nerve fiber recovers its excitability rapidly so that after the spike its membrane is again ready to conduct another impulse. The after-potentials are related in some unknown way to oxidative recovery and to ionic unbalance. In addition, the excitability of a nerve is enhanced during the negative after- potential (catelectrotonus) and is diminished during the positive after-poten- tial (anelectrotonus) (Fig. 294). Cervical sympathetic after-potential. I I I I I I ! I >140r 0 . 20 XI :§ 100 i i 140r '. I I I I 60 80-, Cervical sympathetic ^. 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 Prosser, C. Ladd (Clifford Ladd), 1907-; Bishop, David W. Philadelphia, Saunders
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