Aging is a natural phenomenon. it is the law of nature this slide is about the various factors which independently or in combinations contribute to aging in humans

1. Aging
The biology of senescence

2. Topics to cover
• Aging
• Types of Aging
• Theories related to aging
• Causes of Aging
• Life span
• Senescence
• conclusion

3. Definition of some terms
• Senescence – The process of aging at the cell and
organismal levels.
• Gerontology – is the branch of biomedical sciences
that studies aging.
• Lifespan – Longest time that species is capable of
living. (110 years for humans)
• Life expectancy – the amount of time a member of a
species can except to live. (72-76 years for humans)

4. What is Aging?
• Aging is the progressive accumulation of changes with
time , associated with or responsible for the ever
increasing susceptibility to disease and death which
accompanies advancing age.
• These changes create a normal physiologic decline seen
in middle and late adulthood.
 Changes during puberty
 Graying of hair

5. Primary aging
• Physiologic changes associated with age.
• Lungs & heart function decreases with age.
• Cellular immune system is most affected.
• Liver & kidney functions diminishes as well.
• Decrease in homeostatic reserve & therefore
elderly people cannot tolerate various diseases
stress.

6. Secondary aging
• Is the increased rate of aging changes that stems
from disease & psycho-socio-economic problem.
• Chronic diseases have mostly replaced acute
illness.
• Diabetes, rheumatic diseases, chronic CVD
smoking, poor nutrition & lack of exercise.
• To some degree it is Reversible & Controllable so
prevention & early detection is of paramount
importance

7. Senescence
• The process by which a cell looses its ability to
divide, grow, and function. This loss of function
ultimately ends in death.
A degenerative process, only.
Has no positive features.

8. Symptoms of normal aging
• EXTERNAL
• More grey hair on your head.
• Skin is not as smooth as it used to be.

9. Distinction between different ageing processes
1) UNIVERSAL AGEING : age changes that all people share
2) PROBABILISTIC AGEING : age changes that may happen to some , but not all people
as they grow older for e.g. : onset of type II diabetes.
3) CHRONOLOGICAL AGEING : it refers to how old a person is.
4) SOCIAL AGEING : society’s expectations of how people should act as they grow older.
5) BIOLOGICAL AGEING : an organism’s physical state as it grows.
6) PROXIMAL AGEING : age-based effects that comes about because of factors in the
recent past.
7) DISTAL AGEING : age-based differences that can be traced back to cause early in
prison’s life.

10. Groups of Aging theories
• There are 2 main groups of aging theories
• First - aging is natural & programmed in the body,
while
• second - aging is a result of damage which is
accumulated over time.
• Complex interaction of genetics, chemistry,
physiology & behavior.

11. Programmed Theories
• Assert that the human body is designed to age
(biological timeline).
Programmed Senescence Theory
Neuroendocrine Theory
Immunological Theory
Cellular clock theory
Telomeric Theory

12. Theories of Aging
• Programmed longevity - caused by genes switching “on” &
“off” over time.
• E.g., Hay flick's Limits
Fibroblast was removed from Umbilical cord & cultured
it divided & re-divided until 50 divisions after this point it
cannot divide further
• Neuroendocrine theory - changes in hormones control
aging.
• E.g., Menopause – there is Decreased level of estrogen &
progesterone, Hot flashes & insomnia

13. • Immunological theory - programmed to decline
over time, leaving people more susceptible to
diseases.
• E.g., Decreased T cells in adults
- leads to increased diseases in older adults
- increased autoimmune diseases in adults
• Cellular clock theory - cells hitting their
programmed reproductive limit.

14. Telomeric Theory
• This is an extension of the “Hayflick Limit.”
• Telomeres are specialized DNA sequences at
the end of chromosomes.
– They shorten with each cell division.
– When the telomeres become too short, the cell enters
the senescence stage.
• In the normal process of DNA replication, the
end of the chromosome is not copied exactly,
which leaves an un-replicated gap.

16. Telomeric Theory
• Shortened telomeres are found in:
– Atherosclerosis
– Heart disease
– Hepatitis
– Cirrhosis

17. Telomeric Theory and Cancer
• 90% of cancer cells have been found to
possess telomerase.
– Telomerase prevents the telomere from
shortening.
– This allows the cancer cells to reproduce, resulting
in tumor growth.
• Research areas
– Measuring telomerase may help detect cancer.
– Stopping telomerase may fight cancer by causing
death of cancer cells.
– Telomerase may be used to help with wound
healing or the immune response.

18. Error theories
• Assert that aging is caused by environmental damage to
our body’s systems, which accumulate over time.
Wear & Tear theory
Rate of living theory
Cross linking theory
Free radical theory
Catastrophe theory
Somatic mutation theory

19. • Wear & tear – oldest hypothesis that cells & tissues simply
wear out with time.
• E.g., wearing out of the skeletal system such as in
osteoarthritis
• Rates of living – faster an organism uses oxygen, the shorter
it lives.
• E.g., animals with rapid metabolism tend to have the shortest
lifespan i.e., birds.
• Studies examining the relationship between metabolic rates
and longevity have produced inconsistent results, limiting the
usefulness of this theory.

20. • Cross-linking (glycation) - cross linked proteins
accumulate & slow down body processes.
• E.g., non-enzymatic glycosylation reaction occur when
glucose molecules attach to proteins causing a chain of
chemical reactions resulting in a structural change to the
proteins
- loss of flexibility of connective tissue
- micro vascular changes in arteries
• Genome error - genetic mutation causes cells to
malfunction

21. • Free radicals (oxidative stress) – cause
damage to cells & eventually impairs function.

22. Free radical cycle
The free radical “grabs” a electron from
any molecule it its vicinity.
It does this because electrons like to exist
in pairs.
When it “grabs” an electron from another
molecule, it damages the other molecule.

23. Free Radicals
As the free radical (green) attacks the membrane it
can release another type free radical (blue).

24. Damaged membrane
The free radical (blue) attacks the DNA releasing another
free radical (purple).
mitochondrion
Free Radicals

25. anti-oxidant
molecule
Repaired
membrane
damaged
DNA
The anti-oxidant molecule destroys the damaging free radical. The membrane
repairs itself, but the DNA remains damaged, impairing the cells function. In
addition, the anti-oxidant molecule now has an unpaired electron and thus becomes
a new radical.

26. Free Radical Theory
• Free radicals do not go unchecked. The body
has a multi-layered defense system that reacts
and detoxifies the damaging radicals.
• Defenses include:
– Natural antioxidants in the body, such as bilirubin.
– Enzymes such as superoxide dismutase (SOD),
catalase, & glutathione peroxidase.
– Dietary antioxidants such as beta carotene, and the
vitamins C and E.

27. Can This Stop Aging?

28. Somatic Mutation
• Genetic mutations occur and accumulate with
age in the somatic cell causing the cell to:
– Deteriorate
– Malfunction
• Accumulation of mutations result in :
– Damage to the DNA
The theory states that aging is an imbalance between
DNA’s ability to repair itself and accumulating DNA
damage.
– When the damage exceeds the repair, the cell
malfunctions and this can lead to senescence.

29. DIVISION OF THE LIFE SPAN
Both human and animal’s life is often divided into various ages
1)Juvenile[via infancy/childhood/adolescence(0-19)]
2)Early adulthood(20-39)
3)Middle adulthood(40-49)
4)Late adulthood(60 and rest of the life)
Ages can also be divided into decades
Terms ages
1)Denarian 10-19
2)Vicenarian 20-29
3)Tricenarian 30-39
4)Quadragenarian 40-49
5)Quinquagenarian 50-59
6)Sexagenarian 60-69
7)Septuagenarian 70-79
8)Octogenarian 80-89

30. WHAT IS SENESCENCE?
Senescence refer to state or process of ageing.
There are different types of senescence. They are
1)NEGLIGIBLE SENESCENCE :
Numerous species show very low sign of ageing this is known as
negligible senescence for e. g fishes like lake trout and the rock fish,
invertebrate like sea anemone and lobster.
2)CELLULAR SENESCENCE:
In human and other animals, cellular senescence has been
attributed to the shortening of telomeres with each cell cycle, when telomere
become too short, the cell dies. The length of the telomeres is therefore the
“molecular clock” predicted by hay flick. Telomere length is maintained in
immortal cell for e.g. germ cells and keratinocytes stem cells but not other skin
cell types.

31. CAUSES OF AGEING
Ageing can be as a result of animal’s genetic set up and can be due to
environmental factors, nutritional influence, social and psychological
reasons.
1)GENETIC SET UP AS A CAUSE
It is found even under ideal condition an organism is destined to age
and die at particular time. So far, no animal or plant is found to be
immortal. The genetic setup must be influencing this phenomenon like
any other psychological activity of an organism.
2)ENVIRONMENTAL INFLUENCE
The surrounding in which the organism lives affect a lot by a way of
pollution, stress etc.

32. 3) INFLUENCE OF NUTRITION AND HEALTH PRACTICE ON
AGEING
• Nutritional status of an animal can affect the ageing
process. Lack of essential nutritional component needed
for a healthy living can enhance ageing process.
Irregularity of meals, lack of sleep, smoking habits,
alcohol consumption, lack of exercise, tension and
worries etc., cumulatively cause in enhancing ageing.
4) SOCIAL AND PSYCHOLOGICAL INFLUENCES
• Psychological factors like insecurity, stress etc. can
largely affect the organisms, life span. Stress can be
psychological, occupational and nutritional also.

33. PREVENTION AND REVERSAL
•Several drugs and food supplements have been shown to
retard or reverse the biological affects of ageing in animal
model
•Resveratrol: a chemical found in red grapes, have been
shown to extend the Life span of yeast by 60%
•The combination of Acetyl-L-cartinine and α-lipoic acid if
been fed to rat produce a rejuvenating affect.
•Rapamycin: is generally used to suppress the immune
system and prevents the rejection of transplanted organs.
•By using cosmetics also we can look some year younger

34. Can you delay or stop aging by taking
vitamins and other free radical scavengers?
• There is no evidence-based proof that dietary
supplements delay or stop aging. This is a big
area of nutrition quackery. BEWARE!
• Remember, there is a lot of evidence-based
proof that taking some supplements
INCREASES cancer rate, for example lung
cancer. Smokers who take beta-carotene
supplements have higher lung cancer rates than
smokers not taking these supplements.
• Therefore, the risk/benefit ratio is in favor of
NOT taking SUPPLEMENTS to retard aging.

35. CONCLUSION
1) Ageing is a universal truth of life on earth.
2) Ageing is a process that is witnessed globally i.e.
irrespective of place in any part of the world.
3) Ageing affects all individual of species.
4) But recent development in science and technology
has helped to overcome Senescence to a certain
extent.

36. The End

37. REFERENCES
• 1) Development biology
- Scott f. gilbert
• 2) Development biology
- Leon. W. Broader
• 3) Cell biology, genetics and developmental biology
- k. sharada and Mathew Joseph
4) www.en.m.wikipedia.org/wiki/Ageing
5) www.d.sc.discovery.com
6) www.uga.edu.com