The areas of the tongue sensitive to tastes. The classical theory about the physiology of taste recognizes the existence of four fundamental tastes - sweet, salty, sour and bitter - each being perceived by specific areas of the tongue by means of gustatory receptors, also known as taste buds.
Theories of Aging. Theories of Aging. Erik Erikson, who took a special interest in this final stage of life, concluded that the primary psychosocial task of late adulthood (65 and beyond) is to maintain ego integrity (holding on to one's sense of wholeness), while avoiding despair (fearing there is too little time to begin a new life course).
Theories on Aging. Why do we age? Although the question has been raised since hundreds of years ago, the mysteries that control human life span are yet to be discovered. During the last decades, many theories have been proposed to explain the process of aging, but neither of them seems to be fully satisfactory. Instead, these theories interact with each other and all of these together contribute to aging. The image below shows different mechanisms that have been proposed to explain aging. In this module, however, we will only discuss three major theories of aging: cellular senescence, DNA damage, and telomere shortening. Cellular Senescence