Physiology of human ageing

• Random molecular damage during cell replication
• Inactivity, poor diet and inflammation increase damage
• Redution in the body’s adaptive reserve capacity (resilience)

Proposed factors contributing to ageing

• Mutations in chromosomes
• Mutations in mitochondria
• Intracellular aggregates
• Extracellular aggregates
• Cellular loss (lack of stem cells/cell replacement)
• Cell senescence (useless/harmful cells)
• Extracellular protein crosslinks

Ageing hypothesis

• DNA damage - affects cell renewal and stem cells prevent cell repair
• Free radical theory - mitochondria produce free radicals which produce oxidative stress which accumulates with age
• Telomeres - tips of chromosomes, shorten with cell division over time which leads to cell senescence
  • ‘Hayflick limit’ - the number of times a normal human cell can divide before cell division ceases
• Cross-linking theories - tendons, skin and blood vessels lose elasticity

Disposable soma hypothesis

• Repair and maintenance of a body takes energy and resources
• After reproduction there is little evolutionary value in repairing and maintaining the body