. Principles of modern biology. Biology. EPITHELIUM NERVE ENDING PAIN RECEPTORS Fig. 23-2 Free nerve ending in epithelium. The ter- minal branches of the afferent nerve fiber end freely among the epithelial cells. Fig. 23-1. Some types of mechano- receptors of vertebrates. A, tactile cor- puscle (touch receptor) from the skin. B, Pacinian corpuscle (pressure recep- tor), found in deeper layers of the skin and in many internal organs. C, Golgi organ (proprioceptor) on a tendon. D, muscle spindle (proprioceptor) in skele- tal muscle, n, afferent nerve fibers; c, connective tissue capsules; t, te
. Principles of modern biology. Biology. EPITHELIUM NERVE ENDING PAIN RECEPTORS Fig. 23-2 Free nerve ending in epithelium. The ter- minal branches of the afferent nerve fiber end freely among the epithelial cells. Fig. 23-1. Some types of mechano- receptors of vertebrates. A, tactile cor- puscle (touch receptor) from the skin. B, Pacinian corpuscle (pressure recep- tor), found in deeper layers of the skin and in many internal organs. C, Golgi organ (proprioceptor) on a tendon. D, muscle spindle (proprioceptor) in skele- tal muscle, n, afferent nerve fibers; c, connective tissue capsules; t, tendon; m, muscle fibers. as is shown in the case of a tactile corpuscle (Fig. 23-1 A). Such receptor cells are usually separate from the sensory nerve cells, which conduct the excitations to the central parts of the nervous system; but in some cases— lor example, the pain receptors—the sensory nerve cells act as conductors as well as re- ceptors (Fig. 23-2). The receptors of touch and temperature are restricted mainly to the superficial parts of the body, especially in the skin, and on the lips and cornea; but pressure and pain receptors are also found in many deep-lving parts. Receptors of Taste and Smell. Each ani- mal discovers and recogni/es its food by means of chemoreceptors, which are ex-. 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 Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
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