Ageing or Senescence?
Ageing and senescence are related words that are often used interchangeably, but there are notable differences. Both ageing and senescence are processes characterized by progressive changes in the tissues of the body, eventually leading to a decline in function and death of the organism.
Senescence refers to a post-maturational process that leads to diminished homeostasis and increased vulnerability of the organism to death.
Ageing, in contrast, refers to any time-related and continuous process that starts at conception and continues until death. The mechanisms involved in ageing are partially intrinsic to the organism (genetic and epigenetic factors), and partially external ( such as nutrition, radiation, temperature and stress.) Numerous theories have evolved to improve our understanding of the ageing process in order to formulate strategies that enhance extension of life.
Theories of ageing are classified into three groups based on the level at which the ageing mechanism is targeted: Evolutionary theories, Systemic theories, and Molecular and Cellular theories.
Evolutionary theories state that ageing results from a decline in the force of natural selection. Because evolution acts primarily to maximize reproductive fitness in an individual, longevity is a trait to be selected only if it is beneficial for fitness. Life span is, therefore, the result of selective pressures and may have a large degree of plasticity within an individual species.
In the Molecular and Cellular theories, the ageing process is related to the decline of organ systems essential for control and maintenance of other systems within the organism. These theories attempt to delineate mechanisms of the ageing process at the cellular and sub-cellular levels.
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