On the other hand, other theories support the idea that aging is a regulated process, mainly by the genetic code, such as the telomere length, the number of divisions that a somatic cell can go. Aging is associated with two joint processes, progressive cell degeneration and the loss of regenerative capacity. Programmed aging in the past, many investigators tried to develop a unified theory of biological aging. Other studies suggest that aging is controlled by the thymus.
Programmed theory is the idea that aging is genetically programmed to occur with time, and this process of deterioration. The decreased immune function, especially in the thymus and bone marrow, is the basis for the lack of general wellbeing that leads to aging. The three main systems that are connected with aging are the endocrine hormonal system, the immune system, and our genes. Chapter 2 the biology of aging thieme medical publishers. The hayflick limit is a concept that helps to explain the mechanisms behind cellular aging. The programmed theories imply that aging follows a biological timetable regulated by changes in gene expression that affect the systems responsible for maintenance, repair and defense responses, and the damage or error theories emphasize environmental assaults to living organisms that induce cumulative damage at various levels as the cause of aging. The programmed theories imply that aging follows a biological timetable regulated by changes in gene expression that affect the systems responsible for maintenance, repair and defense responses, and the damage or error theories emphasize environmental assaults to living. This theory is considered an interactionist explanation of the aging process.
But based on the classical neodarwinian understanding of population genetics, there are powerful theoretical reasons to believe that aging could not have evolved as an adaptation. Programmed theories now lets let frank explain programmed theories. The programmed theories imply that aging follows a biological timetable. Modern programmed aging theories contend that we age because we possess what amounts to a biological suicide mechanism or program that purposely limits lifespan to a speciesspecific value in order to obtain an evolutionary benefit. Inequalities among the aged exist along the lines of gender, raceethnicity, and social class. Modern programmed aging theoriescontend that we age because we possess what amounts to a biological suicide mechanism or programthat purposely limits lifespan to a speciesspecific value in order to obtain an evolutionary benefit. Modern biological theories of aging in humans currently fall into two main categories. The hayflick limit the embryo project encyclopedia. There are compelling reasons to regard aging as an evolved adaptive program.
A mammal aging theory could avoid explaining nonmammal evidence. There are a number of non programmed theories associated with aging. A protective segment of dna located at the tip of a chromosome. Unlike the earlier programmed theory of evolution and aging, which tried to findreasonswhyevolutionmight favor aging, evolutionary senescence theory focuses on the failure of natural selection to affect latelife traits. Aging, here defined as increasing mortality with in creasing chronological. Programmed aging theories are based on the idea that from conception to death, human development is governed by a biological clock. Sep 27, 2011 programmed ageing is thus most appropriately considered in the context of the adaptive theories which suggest positive selection for a controlled termination of life. The first group consists of programmed causes, with timed functional changes, and is generally based on genetic theories. The genetic theory of aging, concepts, and evidence. Theories of aging and their implications for medical research. Both classes of these aging theories are riveting and have been supported by much scientific research. This may be controlled neurologically or hormonally through the hypothalamus. Senescence consists of these manifestations of the aging process. Theories of human aging of molecules to society medcrave.
According to this theory, aging is programmed by genes. Cellular theories of aging propose that human aging is the result of cellular aging, whereby an increasing proportion of cells reach senescence, a terminal stage at which cells will cease to divide. What is the major difference between a programmed theory. The concept of the hayflick limit revised alexis carrels earlier theory, which stated that cells can replicate. But aging is not simple and to understand what aging is and what it means to people experiencing it requires consideration of these points. A logic model is one commonlyused tool for illustrating an underlying program theory. Theories of aging american federation for aging research. In addition, aging theories generally apply only to multiparous or iteroparous gradually aging organisms. Oct 11, 2018 journal abstract evolution of aging theories. Aging is the sequential or progressive change in an organism that leads to an increased risk of debility, disease, and death. Programmed and nonprogrammed theories of aging springerlink.
Genetic theories of aging propose that aging is programmed within each individuals genes. Programmed aging theories are based on modifications to darwins mechanics and extensions to medawars ideas to the effect that aging, although adverse to individuals, benefits populations and that therefore species evolved. If we were building a house or other complex structure, we would need a plan and a schedule. Views of aging based on the concept that the processes of aging are governed, at least in part, by genetic factors.
The programmed theory of aging assumes that the aging is unfolded on the basis of speciesspecific genetic program. That means that aging and death, according to this theory, are not a result of wear and tear or exposure, but are a programmed, natural and necessary part of. Jan 26, 2020 programmed theories of aging assert that aging is an essential and innate part of the biology of humans and that aging is programmed into our body systems. Jul 26, 2009 immunological theory a programmed decline in the immune system leads to increased vulnerability to infectious disease, aging, and eventual death. But aging is not simple and to understand what aging is and what it means to people experiencing it requires consideration of.
On the programmednonprogrammed nature of ageing within the. After a study of the different definitions and theories of aging, none of them explains the process in its entirety, since aging is considered to be a multifactorial process warner et al. In fact, ageing has been defined as the collection of changes that render human beings. For example, there are specific programmed events in the life of a cell, but cells also accumulate genetic damage to the mitochondria due to free radicals and the. The evidence is diverse, deriving from genetics, breeding experiments, and plasticity of life span in stressful environments. Programmed or adaptive aging theory is based on the thesis that aging, described as agerelated increasing mortality, is a physiologic function. Gene theory, which considers aging to be the result of a sequential switching on and off of certain genes, with senescence being defined as the time when ageassociated deficits are. These theories are relate to the accumulative deterioration of bodily processes and include. Programmed theories of aging assert that aging is an essential and innate part of the biology of humans and that aging is programmed into our body systems. There are two modern evolutionary theories of aging.
This theory, defined by harman 49, has been one of the handiest in recent. However, each of these biological senescence theories has faults. The most widely accepted overall theory of aging is the evolutionary senescence theory of aging. May, 2017 2 developmentalgenetic theories this theory consider the process of aging to be part of a continuum with development genetically controlled and programmed. Pdf medical practitioners have for centuries been devising and successfully. Genetic basis of aging theories hi h ti f i lifhigh conservation of maximum life span between species similarity of attained age between monozygotic twins compared to dizygotic twins or nontwin siblings. Programmed aging theories are based on modifications to darwins mechanics and extensions to medawars ideas to the effect that aging, although adverse to individuals, benefits populations and that therefore species evolved biological mechanisms that internally limit their lifespans. The programmed longevity theory of ageing focuses solely on intrinsic ageing factors, being based on the concept that all cells have a pre programmed lifespan before they become defunct 10.
Theories of aging part 2 the programmed theories of aging. This clock sets the appropriate times for various changes to take place. Note that aging theories tend to vary widely in scope. Theories of aging part 2 the programmed theories of. Evolutionary senescence theory, the immunological theory, the free radical theory, and the programmed longevity theory. The aging process is the gradual, decreased ability of the body to function and to heal itself. Programmed aging mechanisms programmed aging theories suggest that aging is a biological function that serves an evolutionary purpose by limiting organism lifespans in order to obtain a speciesunique optimum lifespan. This theory falls into the more general conflict theory of society. Program theory explains why a program is expected to work and a logic model illustrates a program theory. Overview of programmed theories of aging verywell health.
On the programmednonprogrammed nature of ageing within. The theories to explain the aging could be put into two groups. From the donner laboratory of biophysics and medical physics, university of california, berkeley the phenomenon of growth, decline and deathaginghas been the source of considerable speculation 1, 8, 10. Programmed aging theories definition programmed or adaptive aging theory is based on the thesis that aging, described as agerelated increasing mortality, is a physiologic function. Disengagement theory is a theory of aging, it has been given by elaine cumming and william earle henry in their book growing old in 1961. At the root of programmed theories of ageing is the idea that ageing is not a res. For the theories that attempt to explain aging without considering evo. The definition of aging itself is open to various interpretations 14, 79. Stochastic chance theories posit that aging events occur ran domly as genetic mutations and accumulate with time, whereas the programmed senescence theories hold that aging is prede termined and is a function of structured genetic expression. The aging process is defined in this module as follows. This theory entails that all individuals tend to disengage or detach themselves from the larger society i. For example, freeradical theory emphasizes the central role of free.
According to the programmed theories, aging depends on biological clocks regulating. In biological terms this process is described as cell senescence. If ageing is assumed to have evolved in a nonadaptive way, there seems no reason to suppose that such a welldefined programme would exist. Evidence that environmental factors can induce mutations and damage cells, and that repair processes are a normal part of cell function, led to development of error and damage theories of aging. This will limit the bodys ability to regenerate and to respond to injury or stress. Older people experience agebased prejudice and discrimination. Aging by program there is strong evidence supporting the suggestion that aging is in some manner programmed into each species, including humans. The wear and tear theory, also known as deterioration theory was first proposed by roger bacon in the 12th century. The term genetically programmed is used to mean an adaptive function such as weismanns theory. Aging by program, where biological clocks act through hormones to control the pace of aging.
They are generally divided into two major groupings. This theory finds support in the fact that people with parents who have lived long lives are likely to live long themselves. Pdf there are compelling reasons to regard aging as an evolved adaptive program. According to this theory, genes dictate cellular longevity. Supporting evidence for the genetic basis of aging and maximal life span comes from the recognition of genetic diseases of precocious aging, such as in genetic progeroid syndromes. In order to understand the programmed adaptive aging vs. Aging theory focusing on the limits of cell division. The concept states that a normal human cell can only replicate and divide forty to sixty times before it cannot divide anymore, and will break down by programmed cell death or apoptosis. The image below shows different mechanisms that have been proposed to explain aging. The changes in vision, loss of calcium in the bones, decreasing hearing acuity and lowered vital capacity of the lungs are all examples of. Programmed cell death, or apoptosis, is determined by a biological clock via genetic information in the nucleus of the cell. In fact, a first subject is the explanation of the why of aging in evolutionary terms and another subject is the how of aging. The cell is a complex, physical structure, and as it ages, it will develop an issue. Gene theory, which considers aging to be the result of a sequential switching on and off of certain genes, with senescence being defined as the time when ageassociated deficits are manifested.
Emerging programmed aging mechanisms and their medical. Feb 12, 2018 programmed aging theories such as disposable soma theory, mutation accumula tion theory, and antagonistic pleiotropy theory attack each other. Psychological theories relate these transitions to personality or ego development and. Another key difference is that, while a logic model can just use an arrow to show that one thing leads to the next, your program theory needs to lay out the evidence to show why you believe one thing will lead to the next. From the donner laboratory of biophysics and medical physics, university of california, berkeley the phenomenon of growth, decline and death aging has been the source of considerable speculation 1, 8, 10. In this, there is no doubt of maximum life span that is the lives span is dependent upon the various species. Theories of aging definition of theories of aging by. A theory only intended to explain human aging could ignore conflicting nonhuman evidence. At the end of this section, there are a number of examples and worksheets that can help you develop a program theory and logic model. Aging, aging theories, deductive analysis of impossibility, evolvability theory, mutation. Dec 14, 20 instead, these theories interact with each other and all of these together contribute to aging. Current theories of aging at the cellular and molecular level generally revolve around two themes. Together, the cellular theories of aging look at the mechanistic aging of a cell. Aging is necessary, it is suggested, either as a means to prevent.
Why modern programmed aging concepts are transforming medical research. A subjects of aging theories it is essential to make a distinction about the specific topics of aging theories. Genetic basis of aging theories hi h ti f i lifhigh conservation of maximum life span between species similarity of attained age between monozygotic twins compared to dizygotic twins or nontwin siblings examppp gyles of exceptional longevity within families. In this module, however, we will only discuss three major theories of aging.
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