The Biology of Ageing

Question 0

What is the worldwide average life expectancy

Answer 0

67. 2 years
    - women 69.5
    - men 65

Question 1

Why has average life expectancy increased over time

Answer 1

Advances in sanitation and medicine

Question 2

What are the possible reasons why women on average live longer than men

Answer 2

1. Delayed onset of cardiovascular disease in women due to oestrogen (reservatol in red wine is structurally the same as oestrogen so it can prevent cardiovascular disease)
2. Women have lower iron levels than men (due to menstruation) - iron is involved in the formation of damaging free radicals which damage cells
3. Young men engage in risky behaviour = more deaths
4. 2 X chromosomes makes it less likely that the same deleterious mutations on the X chromosome are expressed eg one X can mask the other mutated one but with men that 1 X will be expressed

Question 3

What are the major causes of deaths in the US and western world and name the %

Answer 3

Heart disease 26.6
Malignant neoplasms (cancer) 22.8
Cerebrovascular disease (stroke) 5.9
Chronic lower respiratory disease 5.3
Accidents 4.8
Diabetes 3.1
Alzheimer's disease 2.9
Influenza & pneumonia 2.6
Kidney disease 1.8
Septicaemia 1.4 
All except accidents are age related diseases

Question 4

What do eye diseases increase with

Answer 4

Age

Question 5

If heart disease and cancer were eradicated why would humans still be unlikely to live much beyond 100-110 years

Answer 5

• genetically programmed cessation of mitosis (cells stop dividing with age)
• damage to the body’s DNA (as mechanism to repair damage declines so accumulate more harmful mutations with age)
• breakdown in the accuracy of protein synthesis
• changes in neuroendocrine function (make wrong hormones with age or not enough right ones)
• decline in immune function (white blood cells break down)
• an increase in cellular free radical injury

Question 6

What are the normal changes associated with ageing

Answer 6

• cellular/morphological changes
• connective tissue changes
• reproductive system changes
• multi sensory deterioration
• immune system decline

Question 7

What happens during cellular/morphological changes

Answer 7

1. Cell loss - especially significant in amitotic tissue (cells which don’t replicate) with age the cells become bigger to fill space so more irregular ie mitosis decreases eg cannot replicate cardiac muscle to brain cells die.
   Loss of skeletal & smooth muscle as it breaks down with age eg wasting of iris dilator muscle may account for senile miosis so need higher levels of light to see
2. Changes in cellular organelles eg mitochondria and endoplasmic reticulum so makes the wrong protein or not enough or can’t regenerate the energy we need
3. Accumulation of lipofuscin eg RPE As it fails to rid of waste in the eye with age
4. Accumulation of advanced glycation (sugar binded at end of protein) end products cause cross linking between proteins (eg blood vessels becomes less elastic) & cross linking between crystallines is associated with cataract (when lens fibres bind with each other & cause opacities)
5. Irreversible DNA damage, repair mechanism slows down as age can cause cancer with older people
   Part of chromosome called telomere (a non coding part of DNA, as the cell divides the same telomere removes) which protects DNA from fraying & decoding ie protects the coding parts of the DNA, so it is a repetitive nucleotide sequence at each end of chromosome. Telomere decreases with age so can get cancer due to chromosomes/DNA get damaged during cell division

Question 8

What happens during connective tissue changes (fibres not cells)

Answer 8

1. Elastic tissue changes eg wrinkles and loss of arterial elasticity leading to increase blood pressure with age
2. Enzymes that destroy collagen are unregulated, so destroys collagen with age eg ptosis
3. Changes in cartilage in joints - osteoarthrosis
4. Loss of bone - osteoporosis eg spine collapses
5. Hair loss of mass and pigment

Question 9

What happens during reproductive system changes

Answer 9

Menopause

Question 10

What happens during multisensory deterioration

Answer 10

Senses become less acute eg 
Vision
Semicircular canals = less balance as vestibular system deteriorates with age 
Hearing - presbycusis 
Taste - decreases 1% per year
Smell - chemoreceptors decrease 
Pressure - touch decreases 
Temperature 
Proprioception - know where limbs are 
Pain - loss of corneal sensitivity with age

Question 11

What happens during immune system decline

Answer 11

Increase chance of infection in the elderly

Question 12

What do normal ageing processes represent

Answer 12

A gradual deterioration in bodily function onto which superimposed periods of more rapid decline due to disease

Question 13

What are the ultimate causes of ageing

Answer 13

1. Tissues accumulate too much unavoidable damage that cannot be repaired during an animals life so have reached limit of what is biologically possible
2. There is a evolutionary disadvantage to ageing

Question 14

What are the evolutionary disadvantages to ageing

Answer 14

1. The old make little contribution to rearing offspring and use up resources better allocated to the young
2. Antagonistic pleiotrophy- some genes that may be beneficial early in life but have deleterious effects in old age eg testosterone is good in young but for older can cause prostate cancer