Tactile sensations from the oral-facial region serve unique functions in all vertebrate species. In nonprimate mammals, facial tactile receptors are used to explore the environment as a supplement to visual information obtained as the animal explores new and unfamiliar territory. In previous chapters we already have noted that the highest density of thermoreceptors and nociceptors exists on the face and that thermal signals serve a dual sensory and thermoregulatory role. The density of mechanoreceptors, a group of sense organs that signal low-threshold or innocuous mechanical deformation of the skin or associated hairs, is also highest in oral-facial regions. Most mammals have developed a type of hair uniquely suited for exploratory function that are called vibrissae or whiskers. These specialized hairs are densely innervated by different types of mechanoreceptors and are often associated with muscle tissue that provides efferent or motor control. Thus, rodents exhibit very regular patterns of movement of their vibrissae as they search their surroundings.
KeywordsReceptive Field Position Detector Hairy Skin Free Nerve Ending Guard Hair
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