Lecture (2)Physical Therapy for Geriatrics Dr. Samah Alsaid

Theories of Aging(a)

Theories of Ageing Genetic theories deal with speculations regarding the identity of aging genes, accumulation of errors in the genetic machinery and telomeres. Biochemical theories are concerned with energy metabolism, generation of free radicals, the rate of living, and the health of mitochondria. Physiological theories deal entirely with the endocrine system and the role of hormones in regulating the rate of cellular senescence.

Error Catastrophe Theory First 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.

Genes and Programmed Aging The 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.

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

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.

Hormone Imbalance Theory This 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

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

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.

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.

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.