Study Notes on Aging and Senescence
Life Span: Aging and Senescence
Aging vs Senescence
Aging refers to the progression of time and its physical, mental, and social effects.
Senescence is a biological process involving harmful changes at various systemic levels.
Life Expectancy vs Maximum Lifespan
Life Expectancy: Average years a newborn can expect to live based on current mortality patterns.
Maximum Lifespan: Observed maximum survival age; does not vary across populations or sexes (e.g., 122 years).
Key Aspects
Life expectancy varies between populations and sexes.
Period life expectancy summarizes death rates within a specific year.
Significant decline in bone mass related to age, especially in females post-menopause due to osteoporosis.
Physiological Changes
Senescence affects various organ systems: musculoskeletal, immune, endocrine, cardiovascular, and neurological.
Key issues in the cardiovascular system include hypertrophy, ischemia, fibrosis, and atherosclerosis.
Theories of Senescence
Causal Theories:
Mechanistic: Focus on proximate causes and natural processes.
Evolutionary: Addresses ultimate causes related to natural selection.
Hallmarks of Aging Mechanisms:
Cellular senescence, telomere attrition, and protein damage.
Accumulation of senescent cells leads to Chronic inflammation and further cellular damage.
Evolutionary Explanations
Mutation accumulation theory: Negative mutations accumulate due to lack of selection post-reproductive age.
Antagonistic pleiotropy: Some genes beneficial in youth become harmful in old age.
System-Specific Theory: Menopause may enhance survival/fitness, exemplified by the Grandmother hypothesis.