Theories of aging currently studied by modern science range from the concept of purely genetic control of aging to the concept of reducing environmental onslaughts on the human organism. Scientists now believe that the mechanisms that cause aging are extremely complex and variable, and rather than a single cause, may be many phenomena working in concert.
Most theories of aging can be placed into two general categories: error theories and programming theories. Error theories are based on the premise that random events, such as environmental assaults, cause damage to the body cells. This damage accumulates over time resulting in cellular, molecular, and organ malfunction. Programming theories are based on the assumption that aging is programmed into the cell itself and is the expected result of a purposeful sequence of events written into the genes.
One of the oldest theories of aging is the wear and tear theory that states that at the molecular level, DNA is continuously damaged but the body cannot repair the damage, and it accumulates, leading to molecular and finally organ malfunction. The metabolic theory argues that the faster an organism lives, the quicker it is to die. Caloric restrictions appear to be the only factor repeatedly shown to alter the rate of aging in animals, and nutrition would seem to control the change in certain hormones controlling metabolism.
The free-radical theory focuses on the damaging effects of free-radicals, highly unstable chemical fragments produced during normal metabolism that react and damage other molecules. Age-related accumulation of free-radical damage may interfere with the vital work of key cell structures.
Thus, all the various proponents of the error theory state that the body will produce faulty chemicals and proteins which will be synthesized and accumulated. This process leads to damaged cells, tissues, and organs resulting in death.
On the other hand, the programmed senescence theory states that aging and death are due to programmed events, a result of the sequential switching on and off of certain genes. Some may act as a biological clock, such as those controlling puberty and menopause. If aging is programmed, the endocrine or hormone system and the immune system are the two likely candidates which control aging.
Events occurring in the hypothalamus and pituitary glands may be responsible for some important aging processes. The pituitary gland, located at the base of the brain, secretes hormones that in turn stimulate other glands to produce hormones. It is possible that a biological clock in the hypothalamus (a region of the brain) instructs the pituitary gland to secrete a hormone that interferes with the ability of the body tissues to respond to thyroid hormones. This theoretical hormone, referred to by some as the "death hormone," has never been isolated.
The immune system defends the body against bacteria, viruses, and other invading organisms. The thymus gland, located in the chest, is an essential component of the system. It reaches maximum size during adolescence and declines to the point where it is barely visible at age 50. Proponents of the immune system theory believe that by reducing the body’s ability to fight infection, fend off cancer, and even repair DNA damage, the decline in the system may be the single most important event in the aging process.
As can be seen, the study of aging is yet in its infancy, although it seems to be an energetically growing discipline. Understanding the mechanism of aging will presumably help to eliminate diseases and disorders associated with old age and presumably lengthen the active life process. Science is also on the threshold of making changes in the gene itself.
Most theories of aging can be placed into two general categories: error theories and programming theories. Error theories are based on the premise that random events, such as environmental assaults, cause damage to the body cells. This damage accumulates over time resulting in cellular, molecular, and organ malfunction. Programming theories are based on the assumption that aging is programmed into the cell itself and is the expected result of a purposeful sequence of events written into the genes.
One of the oldest theories of aging is the wear and tear theory that states that at the molecular level, DNA is continuously damaged but the body cannot repair the damage, and it accumulates, leading to molecular and finally organ malfunction. The metabolic theory argues that the faster an organism lives, the quicker it is to die. Caloric restrictions appear to be the only factor repeatedly shown to alter the rate of aging in animals, and nutrition would seem to control the change in certain hormones controlling metabolism.
The free-radical theory focuses on the damaging effects of free-radicals, highly unstable chemical fragments produced during normal metabolism that react and damage other molecules. Age-related accumulation of free-radical damage may interfere with the vital work of key cell structures.
Thus, all the various proponents of the error theory state that the body will produce faulty chemicals and proteins which will be synthesized and accumulated. This process leads to damaged cells, tissues, and organs resulting in death.
On the other hand, the programmed senescence theory states that aging and death are due to programmed events, a result of the sequential switching on and off of certain genes. Some may act as a biological clock, such as those controlling puberty and menopause. If aging is programmed, the endocrine or hormone system and the immune system are the two likely candidates which control aging.
Events occurring in the hypothalamus and pituitary glands may be responsible for some important aging processes. The pituitary gland, located at the base of the brain, secretes hormones that in turn stimulate other glands to produce hormones. It is possible that a biological clock in the hypothalamus (a region of the brain) instructs the pituitary gland to secrete a hormone that interferes with the ability of the body tissues to respond to thyroid hormones. This theoretical hormone, referred to by some as the "death hormone," has never been isolated.
The immune system defends the body against bacteria, viruses, and other invading organisms. The thymus gland, located in the chest, is an essential component of the system. It reaches maximum size during adolescence and declines to the point where it is barely visible at age 50. Proponents of the immune system theory believe that by reducing the body’s ability to fight infection, fend off cancer, and even repair DNA damage, the decline in the system may be the single most important event in the aging process.
As can be seen, the study of aging is yet in its infancy, although it seems to be an energetically growing discipline. Understanding the mechanism of aging will presumably help to eliminate diseases and disorders associated with old age and presumably lengthen the active life process. Science is also on the threshold of making changes in the gene itself.