INTRODUCTION
Aging is a biological process that leads to an increasing probability of degenerative diseases. All animals have a definite life cycle which includes birth, a period of rapid growth, puberty, a gradual cessation of growth, senescence, and finally death.
The pattern is rather rigidly fixed by the genetic background of the organism and can be varied only by rather drastic measures. Animals have very efficient repair mechanisms, which allow them to recover from almost any type of damage or disease and yet, in the absence of demonstrable malfunction, the organism degenerates and finally succumbs to one of the degenerative diseases. The impact that aging has on organisms is a complex interaction between the processes of aging at a cellular, organ, and integrated systems level, and the effects of environmental factors such as nutrition, infection and trauma.Biological aging, termed senescence (the process of aging), is one of the most complex biological processes. Aging can be defined as the time-related deterioration of the physiological functions necessary for survival and fertility. Aging is defined as the progressive accumulation of damage over time, leading to disturbed function on the cellular, tissue, and organ levels and eventually to disease and death. It is a multifactorial process where genetic, endogenous, and environmental factors play a role. Aging has been associated with a loss of complexity in a wide range of physiological processes and anatomic structures. Rather, they would consider aging to be the default state occurring after the animal has fulfilled the requirements of natural selection. Lipsitz and Goldberger (1992) first proposed that the aging process may be characterized by a progressive loss of physiologic complexity. We contend that this loss of complexity results in the functional decline of the organism by diminishing the range of available, adaptive responses to the innumerable stressors of everyday life. After its offspring are born and raised, the animal can die. The maximum life span is a characteristic of the species. It is the maximum number of years a member of that species has been known to survive.
There are several levels at which we can study aging, including cellular, biochemical, and genetic studies. Reactive oxygen species (ROS) can damage cell membranes, inactivate proteins, and mutate DNA. Mutations that alter the ability to make or degrade ROS can change the lifespan of the mutants. Mitochondria may be a target for proteins that regulate aging. Aging is the time-related deterioration of the physiological functions necessary for survival and reproduction. The phenotypic changes of senescence (which affect all members of the species) are not to be confused with diseases of senescence, such as cancer and heart disease (which affect individuals) (Figure 25.1).
25.2