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TOUCH Until the beginning of the last century, touch (feeling) was treated as a single sense. Thus, warmth or coldness, pressure, and pain, were thought to be part of a single sense of touch or feeling. It was discovered that different types of nerve ending receptors are widely and unevenly distributed in the skin and mucous membranes. For example, the skin of the back possesses relatively few touch and pressure receptors while the fingertips have many. The skin of the face has relatively few cold receptors, and mucous membranes have few heat receptors. The cornea of the eye is sensitive to pain, and when pain sensation is abolished by a local anesthetic, a sensation of touch can be experienced.
Figure 1-52.-Major parts of the ear. Receptors are classified according to location, structure, and types of stimuli activating them. Classified according to location, the three types of receptors are as follows: superficial receptors (exteroceptors), deep receptors (proprioceptors), and internal receptors (visceroceptors). See table 1-4 for receptor locations and the senses resulting from the stimulation of these receptors. |
 
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