Unit 4 BHS: Theories of Ageing & Physiological effects of ageing Flashcards
Define Biological Ageing
the decline and deterioration of functional properties at the cellular, tissue and organ levels
Identify and define the four characteristics of biological ageing
- universal - occur at different degrees in all individuals of a species
- intrinsic - must be driven by endogenous factors
- progressive - must occur progressively throughout lifespan
- deleterious - must negatively impact the functionality of an individual. (must be “bad” for the individual)
Identify & define the types of ageing
Primary Ageing - inevitable; slow and progressive; loss of reserve capacity in an organ/ organ system; decreased ability to repair damaged cells & tissues; increased susceptibility to disease
Secondary Ageing - age-related diseases and changes that are results of a person’s lifestyle and environment, can be slowed and/or reversed by changes in lifestyle and modern medicine. Characterised by slow and progressive changes in functionality of most organ systems.
Name 3 factors that contribute to ageing
intrinsic factors
extrinsic factors
stochastic events
Name the 4 main categories of the Theories of Ageing
- evolutionary theories
- molecular genetic theories
- cellular theories
- system theories
Explain the evolutionary theories of ageing
Ageing is due to a decline in the force of natural selection. Mutations that affect health at older ages are not selected against (passed reproductive age).
Genes that are beneficial at younger ages become deleterious at older ages.
The soma becomes disposable after reproduction.
Explains the 4 different cellular theories of ageing
- Cell senescence and telomere loss theory - cells have limited number of cell divisions that they can undergo. Ageing is a result of an increase in frequency of senescent cells (stopped at g0 stage of cell cycle). Senescence can be brought on by telomere loss (hayflick limit) - replicative senescence; and/or cell stress - cellular senescence.
telomere loss can be exacerbated by oxidative stress (link to free radical theory)
- Free radical theory - oxidative metabolism produces reactive oxidative species (ROS), these radicals cause damages to lipids, proteins and DNA. Free radicals can also be produced by inflammatory reposes and extrinsic factors such as chemicals and UV radiation. The effects can be reduced by antioxidants i.e. VitA, C, E and mineral selenium.
- Wear and tear theory - ageing is a result of accumulation of normal injury. Systems wear out due to use and results in abnormal functioning.
Evidence for: obese people die younger; never-pregnant women live longer; replacement of worn-out body parts can prolong one’s lifespan.
Evidence against: human body parts can benefit from use. e.g. aerobic exercise improves CVS and lung functioning; sexual activity stimulates repro. system; digestion improves by eating raw fruits.
CONCLUSION: wear-and-tear theory is relevant to secondary ageing, but does not explain primary ageing. - Apoptotic Theory - ageing is an result of programmed cell death
Explain the 3 theories of System Theories of Ageing
- Neuroendocrine theory (change in neuroendocrine control of hormones)
- Immunologic theory (reduced immunological response and increased autoimmunity)
- Rate-of-Living theory (there is an fixed amount of metabolic potential for every living organism)
Factors that contribute to healthy ageing
Minimize exposure of factors that accelerate secondary ageing; good nutrition; regular exercise; minimise stress; regular screening.
Explain the effects of ageing on cellular & tissue levels
Ageing causes cells to divide more slowly, therefore the rate of injury repair declines. This is seen by a reduction in the rate of haematopoeisis in elderlies.
The extracellular matrix produced by cells are changed: collagen fibres become irregular, causing tendons and ligaments to become less flexible and more fragile. Elastic fibres are cross linked by calcium ions causing them to be less elastic. These changes cause wrinkling of the skin tissue and increased risk of fractures in bone tissue, and the walls of arteries also become less elastic resulting in arteriosclerosis which leads to hypertension.
Effects of ageing on the integumentary system
- epidermis thins
- reduced hypodermal fat - loss of insulation
- reduced sweat gland activity & blood supply to dermis - reduced thermoregulation
- decreased number of melanocytes - grey/white hair
- dermal elastic & collagen fibers decrease - wrinkling
Effects of ageing on the muscular system
- loss of muscle fibres in skeletal, smooth and cardiac muscle
- surface area of neuromuscular junction decreases in skeletal muscle - increased delay in contraction
- loss of motor neurons - reduced muscle control
- decreased density of capillaries around skeletal muscle fibres - insufficient blood supply resulting in longer recovery time after exercise and decreased oxygen supply (slow twitch muscle w/ insufficient energy) - weak muscles
Effects of ageing on the nervous system
- decrease in weight and size of brain - loss of motor neurons (loss of motor agility), reduction in grey matter size (memory loss), loss of cerebellar neurons (affects gait & balancing)
- slow reflexes - action potential conduction reduced by deterioration of myelin sheath. reduced synaptic function due to changes in neuromuscular junction.
- structural changes in neurons - rigid plasma membrane (undesirable for action potential generation); irregular ER; neurofibrillar tangles and amyloid plaques (often seen in Alzheimer’s)
- reduced blood supply
- short-term memory loss
Effects of ageing on the general senses
- reduced numbers of pacinian and meissner corpuscles. Remaining ones become distorted and less functional, one becomes less conscious of the sense of touch. Increased risk of skin injuries
- decreased two-point discrimination
- reduced proprioception, balance and coordination
Effects of ageing on the special senses
- Taste: loss of receptors
- Hearing: hair cells in cochlea decrease. hair cell losses in other auditory structures cause imbalance, less sensitivity to gravity - prone to falling.
- Smell - perception decreases (cause unknown)
- Vision - lenses become rigid causing presbyopia and cataracts
