Lecture+2+Theories+of+aging - Definitions of Aging An...

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1 Definitions of Aging An increased liability to death or loss of vigor Not simply the sum total of age-associated diseases Age-related changes are deleterious, progressive, cumulative, and intrinsic A time-based process, although the relationship between aging and time is variable across organisms Opposed to development - which enhances function, aging diminishes function Aging and Antagonistic Pleiotropy Aging is a property of somatic cells, not germ cells There is no selective pressure after reproduction A genetic trait can have an early selective advantage (increasing reproduction) but a late disadvantae (senescence) - antagonistic pleiotropy Aging occurs because of the accumulation of traits with late deleterious effects Disposable Soma Somatic cells are the germ line’s way of making more germ cells From an evolutionary perspective - you don’t need your body after reproduction Aging is the consequence of investing in reproduction, not maintainence
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2 Aging vs. Disease Causes of death due to disease evolved over time 1900 - respiratory, infectious, digestive disease Today - cancer, cardiovascular disease Many diseases are age-related Individuals do not develop all age-related disease, but neither do they exhibit all signs of aging Age-related disease represents a failure of a particular organ or system that may highlight the design weakness of the system or organ Aging and Disease Aging is not the sum of disease People may show signs of aging without overt disease Normal physiology, chemistry, anatomy are prone to failure This failure may occur gradually (aging) or reach a threshold (disease) Multiple systems with mild decline may have more profound consequences than a single disease How Intrinsic or Universal is Aging?
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