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Hub 2021s - Ageing and disease notes
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AGEING AND DISEASE HUB2021SMAJOR THEORIES OF AGEING
AGEING = complex biological process
Decreased function of tissue/organ systems
Continuous process
Leads to increased morbidity/mortality risk
Due to Multifactorial causes
life expectancy (L.E.) is defined as the expected (stats) # years of life remaining at given
age
Average lifespan: average time expected to survive: usually characteristic of POPULATION
(locality influence) rather than a species
Factors That Influence Lifespan
1. body size –smaller animals live, on average, shorter time than large animals
reasons:
small animals prone to predation
smaller animals (usually) have higher heart rates, ↑ metabolic rate, so shorter life
heart rate -↑ heart rate → live shorter
age at sexual maturity – the longer it takes for (some) animals to reach maturity, the
longer they will live afterwards
loss of function of various systems eg:
CNS: every neural activity affected: balance, motor skills, hearing, sight, smell, taste
Cardiovascular & respiratory
Musculoskeletal
Endocrine
Digestive: ↓ efficiency of absorption
ageing accumulative, all systems decline
CARDIOVASCULAR & RESPIRATORY SYSTEMS
diffuse atherosclerosis (arteries → plaque build-up) & hypertension → strokes
arteriosclerosis ↑ arrhythmias (abnormal rhythms) ↑
blood vessels elasticity ↓, - systolic pressure & pulse ↑
elasticity of lung tissue ↓, so lung capacity ↓
lowered capacity for aerobic exercise
, MUSCULOSKELETAL SYSTEM
muscle, bone mass begin ↓ in early adulthood
~ 80y- lost 30% muscle mass (declining strength)
osteoporosis common, esp ♀, immobile people & those on steroids
osteoarthritis v. common
ENDOCRINE SYSTEM
basal metabolic rate ↓ 1% per yr after ~30y
type II diabetes can lead to cardiovascular disease (CVD), renal impairment,
neuropathy, retinopathy
secretion growth hormone ↓ →:
1. ↓ muscle strength
2. ↓ bone mass
3. ↓ fracture healing
4. altered lipoprotein metabolism → ↑ CVD risk
MAJOR THEORIES BEHIND AGEING
EVOLUTIONARY THEORIES
programmed ageing/death
mutation accumulation
antagonistic pleiotropy
somatic mutation
Molecular/ cellular theories
parallel ageing
wear-&-tear
waste accumulation
glycation
error catastrophe
DNA damage
telomere loss/Hayflick limit
dysdifferentiation
rate-of -living
oxidative stress
caloric restriction
MUTATION ACCUMULATION THEORY (Peter Medawar, 1952):
→ results from decline in natural selection
harmful late-acting mutations passed onto offspring; over successive generations -
accumulate in population, lead to various pathologies, & ageing
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