Theories of Ageing

1. Genetic theories deal with speculations regarding the identity of

aging genes, accumulation of errors in the genetic machinery and telomeres.

2. Biochemical theories are concerned with energy metabolism, generation of free radicals, the rate of living, and the

health of mitochondria.

3. Physiological theories deal entirely with the endocrine system and the role

of hormones in regulating the rate of cellular senescence.

1. Error Catastrophe TheoryFirst proposed in the 1960s, suggests that over time,

the number of errors build up to a catastrophic leading to the death of the cell and, possibly, the entire organism.

2. Genes and Programmed AgingThe genes in a multi-cellular organism appear

to be regulating life span.

Defect at the gene level may be through: inappropriate behavior (that is, they are

turning on or off at the wrong time) or through a mutation

that eventually damages the protein product.

3. Telomeres Theory of Aging.• Telomeres (the sequences of nucleic acids extending

from the ends of chromosomes), shorten every time a cell divides.

• Each time a cell divides it duplicates itself a little worse than the time before leads to cellular dysfunction, aging

• Hay flick limit• Telomerase enzyme

4. Rate-of-Living Theory

Simply put, it claims that if you are going to live fast and hard, life will be short.

This theory is concerned with wearing out of non-replicable body parts such as brain, muscles …..ect

It suggest a preventive strategy, involving a reduction in activity level and caloric intake.

5. Hormone Imbalance TheoryThis theory elaborates on wear and tear

by focusing on the neuro-endocrine system. This system is a complicated network of biochemicals that govern

the release of hormones which are altered by the hypothalamus.

As we grow older the hypothalamus loses it precision regulatory ability and the

receptors which uptake individual hormones become less sensitive to them. and this in

turn produces the physical symptoms of age such as: loss of the ovarian cycle in females,

the loss of vigor((حيويه, physical strength, and endurance

6. The free radical theory: free radical : any molecule that has a

free electron, and so it react with healthy molecules in a destructive

way. Because the free radical molecule has

an extra electron it creates an extra negative charge. This unbalanced

energy makes the free radical bind itself to another balanced molecule as

it tries to steal electrons. In so doing, the balanced molecule becomes

unbalanced and thus a free radical itself.

• The oxygen free radical, oxidative phosphorylation. • attack the structure of cell

membranes, including DNA, RNA, proteins, and the lipids in the cell membrane. • Superoxide dismutase

7. The membrane theory of aging:

According to this theory it is the age-related changes of the cells ability to transfer chemicals, heat and electrical

processes that impair it. As we grow older the cell membrane becomes less lipid

(less watery and more solid). This impedes its efficiency to conduct normal function and in particular there is a toxic accumulation. This cellular toxin is referred to as

lipofuscin and as we grow older lipofuscin deposits become more present in the brain, heart and lungs and

also in the skin.

• The cells declining efficiency also means that the essential and regular transfer of sodium and potassium is impaired, thus reducing communication. It is also believed that electrical and heat transfer is also impaired.

8. The mitochondrial decline theory:The mitochondria are the power producing

organelles found in every cell of every organ. Their primary job is to create ATP. Under normal conditions the mitochondria are fiery furnaces and subject themselves to a lot of free radical damage. They also lack most of the defenses found in other parts of the body, so as we age the mitochondria become less efficient, fewer in number and larger. Accordingly, ATP production declines.

9. The cross-linking theory:also referred to as the Glycosylation Theory of

Aging. In this theory it is the binding of glucose to protein, (a process that occurs under the presence of oxygen) that causes various problems. Once this binding has occurred the protein becomes impaired resulting in cross-linking disorders include senile cataract and the appearance of tough, leathery and yellow skin.

It is also theorized that sugars binding to DNA may cause damage that leads to malformed cells and thus cancer.