Nursing Entrance Exam

papillae, and circumvallate papillae. Filiform papillae provide friction that helps the tongue move objects around in the mouth, and they do not contain taste buds. Each small fungiform papilla contains about five taste buds; each large circumvallate papilla contains as many as 100 taste buds. Taste buds are recessed into the surrounding epithelium. Each taste bud contains about 40 slender, spindle-shaped cells of at least four different types. A typical gustatory cell survives for only about 10 days before it is replaced. Gustatory Discrimination: There are four primary taste sensations: sweet, salty, sour, and bitter. There is some evidence for differences in sensitivity to tastes along the axis of the tongue, with the greatest sensitivity to salty-sweet anteriorly and sour-bitter posteriorly. However, there are no differences in the structure of the taste buds, and taste buds in all portions of the tongue provide all four primary taste sensations. Dissolved chemicals contacting the taste hairs bind to receptor proteins of the gustatory cell. The end result of taste receptor stimulation is the release of neurotransmitters by the receptor cell. Taste receptors adapt slowly, but central adaptation quickly reduces one’s sensitivity to a new taste. The threshold for receptor stimulation varies for each of the primary taste sensations, and the taste receptors respond more readily to unpleasant stimuli than to pleasant. For example, we are almost 1000 times more sensitiveto acids, which taste sour, than to either sweet or salty chemicals; further, we are 100 times more sensitive to bitter compounds than to acids. Humans begin life with more than 10,000 taste buds, but the number begins declining dramatically by age 50. Sensory loss in aging individuals becomes especially significant due to a decline in the number of olfactory receptors. As a result, many elderly people report that their food tastes bland and unappetizing, whereas children may find the same foods too spicy. 3. Sight: Vision is the most relied-upon sense of all the special senses. Visual receptors are contained within the eyes. The eyes are elaborate structures that enable the brain to detect light and create detailed visual images. Internal eye structures contribute to vision, while accessory eye structures provide protection.

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