All human beings were created with a life span, and this life span is affected with the ageing process. Ageing therefore is the collection of changes that render human beings progressively more likely to die. It is also good to know that ageing is a natural process, and there is absolutely nothing you can do about it, other than making sure that you eat healthy and well, engage in moderate exercise, and go for your regular checkups.

Human ageing is the physiological changes that take place in the body leading to senescence, the decline of biological functions and of the ability to adapt to metabolic stress. In humans the physiological developments are normally accompanied by psychological and behavioral changes, and other changes, involving social and economic factors, also occur.

Ageing begins as soon as maturity is reached and is as much a part of human life development. The study of ageing is concerned primarily with the changes that occur between the attainment of maturity and the demise of the individual. The goal of research in gerontology is to identify the factors that influence these changes. Application of this knowledge is expected to reduce the disabilities now associated with ageing.

The biological-physiological aspects of ageing include both the basic biological factors that underlie ageing and the general wellness status. Since the probability of death increases rapidly with advancing age, it is clear that changes must occur in the individual which make him more and more vulnerable to disease. For example, a young adult may rapidly recover from pneumonia, whereas an elderly person may die.

• Physiologists have found that the performance of many organs such as the heart, kidneys, brain or lungs shows a gradual decline over the life span.

• Part of this decline is due to a loss of cells from these organs, with resultant reduction in the reserve capacities of the individual.

• Furthermore, the cells remaining in the elderly individual may not perform as well as those in the young.

• Certain cellular enzymes may be less active, and thus more time may be required to carry out chemical reactions. Ultimately the cell may die.

• Bones and associated structures will begin to loss density, and becomes porous, and soften.

The heart: Diseases of the heart are the single largest cause of death after age 65. This with increasing age the heart becomes more vulnerable to disease. Even in the absence of detectable disease, the heart undergoes deleterious changes with advancing age. Structural changes include a gradual loss of muscle fibres with an infiltration of fat and connective tissue. There is a gradual accumulation of insoluble granular material in cardiac muscle fibres. These granules, composed of protein and lipid (fat), make their first appearance by the age of 20 and increase gradually, so that by the age of 80 they may occupy as much as 5–10 percent of the volume of a muscle fibre.

The heart also shows a gradual reduction in performance with advancing age. The amount of blood pumped by the heart diminishes by about 50 percent between the ages of 20 and 90 years. There are marked individual differences in the effects of age. For example, some 80-year-old individuals may have cardiac function that is as good as that of the average 40-year-old individual.

Under resting conditions, the heart rate does not change significantly with age. During each beat, however, the muscle fibres of the heart do not contract as rapidly in the old as in the young. This reduction in power, or rate of work, is due to the age-associated reduction in the activities of certain cellular enzymes that produce the energy required for muscular contraction.

In spite of these changes, the heart, in the absence of disease, is able to meet the demands placed upon it. In response to physical exercise it can increase its rate to double or triple the amount of blood pumped each minute, although the maximum possible output falls, and the reserve capacity of the heart diminishes with age.

Arteriosclerosis, or hardening of the arteries, increases markedly in incidence with age, and is often regarded as part of aging. This is not necessarily true. Arteriosclerosis may appear even in adolescents. In general, blood vessels become less elastic with advancing age. There is a progressive thickening of the walls of larger blood vessels with an increase in connective tissue. The connective tissue itself becomes stiffer with increasing age.

This occurs because of the formation of cross-links both within the molecules of collagen, a primary constituent of connective tissue, and between adjacent collagen fibres. The gradual loss of elasticity increases with resistance to the flow of blood so that blood pressure may increase. This in turn increases the work that the heart must do in order to maintain the flow of blood. On the average, obese people have higher blood pressures than those with normal body weights. Since the incidence of obesity increases with age at least up to the age of 55–60, this factor may contribute in part to the increase in blood pressure with age.

Digestive system: Loss of teeth, which is often seen in elderly people, is more apt to be the result of long-term neglect than a result of aging itself. The loss of teeth and incidence of oral disease increase with age, but, as programs of water fluoridation are expanded and the incidence of tooth decay in children is reduced, subsequent generations of the elderly will undoubtedly have better teeth than the present generation.

While it is true that the secretion by the stomach of hydrochloric acid, as well as other digestive enzymes, decreases with age, the overall process of digestion is not significantly impaired in the elderly. Sugar, proteins, vitamins, and minerals are absorbed from the stomach and intestine as well in the elderly as in the young. Some investigations indicate a slight impairment in fat absorption, but the reduction is probably of little practical significance.

These have important implications for nutrition of the elderly. Nutritional deficiencies can be avoided as long as the diet is varied to assure adequate intake of all nutritional elements. Deficiencies are most likely to develop from poor eating habits, such as excessive intake of carbohydrate with a reduction in protein. In the elderly these deficiencies are most apt to be in the intake of protein, calcium, iron, vitamin A, and thiamine (also called vitamin B1) .

Nervous system: Changes in the structures of the brain due to normal aging are not striking. It is true that with advancing age there is a slight loss of nerve cells in the brain. This is because, in the adult, neurons have lost the capacity to form new neurons by division. The basic number of neurons in the brain appears to be fixed by about the age of 10. The total number of neurons is extremely large, however, so that any losses probably have only a minor effect on behavior. Since the physiological basis of memory is still unknown, it cannot be assumed that the loss of memory observed in elderly people is caused by the loss of neurons in the brain.

Neurons are extremely sensitive to oxygen deficiency. Consequently, it is probable that neuron loss, as well as other abnormalities observed in aging brains, results not from aging itself, but from disease, such as arteriosclerosis, that reduces the oxygen available to areas of the brain by reducing the blood supply.

There are probably functional changes in the brain that account for the slowing of responses and for the memory defects that are often seen in the elderly; and even small changes in the connections between cells of the brain could serve as the basis for marked behavioral changes, but, until more is known about how the brain works, behavioral changes cannot be related to physiological or structural changes. It is known that, because of the slow course of aging, the nervous system can compensate and maintain adequate function even in centenarians.

Human behaviour is highly dependent on the reception and integration of information derived from sensory organs, such as the eye and ear, as well as from nerve endings in skin, muscle, joints, and internal organs. There is, however, no direct relation between the sensitivity of receptors and the adequacy of behaviour, because the usual level of stimulation is considerably greater than the minimum required for stimulation of the sense organs. In addition, an individual adapts to gradual impairments in one sensory organ by using information available from other sense organs. Modern technology has also provided glasses and hearing aids to compensate for reduced acuity in the sense organs.

Vision : Visual acuity ability to discriminate fine detail is relatively poor in young children and improves up to young adulthood. From about the middle 20s to the 50s there is a slight decline in visual acuity, and there is a somewhat accelerated decline thereafter. After age 55 there is little further change. Many people in their 50s adopt bifocal glasses to compensate for this physiological change.

The sensitivity of the eye under conditions of low illumination is less in the old than in the young; that is, “night vision” is reduced. Sensitivity to glare is also greater in the old than in the young.

The incidence of diseases of the eye, such glaucoma and cataract, as characterized, respectively, by increased intra-ocular pressure and opaque lenses), increases with age, but recent advances in surgery and the development of contact lenses have made it possible to remove cataracts and restore vision to many individuals.

Hearing
Hearing does not change much with age for tones of frequencies usually encountered in daily life. Above the age of 50, however, there is a gradual reduction in the ability to perceive tones at higher frequencies. Few persons over the age of 65 can hear tones with a frequency of 10,000 cycles per second. This loss of perception of high frequencies interferes with identifying individuals by their voices and with understanding conversation in a group, but does not ordinarily represent a serious limitation to the individual in daily life. Listening habits and intellectual level play an important role in determining the ability to understand speech, so that there is often a disparity between measurements of pure tone thresholds and ability to perceive speech.

Skin
The primary age change in the skin is a gradual loss of elasticity. Although this basic change plays a role, other factors, such as exposure to the weather and familial traits, also contribute to the development of wrinkles and the pigmentation associated with senescence. The ability of the skin to take up slack and remain closely adherent to the underlying structures is due to the presence of fibres of the proteins elastin and collagen . Studies of the minute structures of the skin show a gradual reduction in elastin. In addition, the collagen fibres show an increase in links which greatly restricts the elastic properties of the collagen network.

The effectiveness of facial massage in retarding the development of wrinkles has not been evaluated under carefully controlled conditions. The application of creams containing female sex hormone stimulates regeneration of skin and improves its elastic properties.

Endocrine: Because of the importance of hormones in the regulation of many physiological systems, impairments in endocrine (ductless) glands have traditionally been cited as important determinants in ageing. It is known that the pancreas secretes insulin, the hormone that regulates the utilization of sugar and other nutrients in the body. When the pancreas fails to produce adequate amounts of insulin, diabetes occurs. One test for diabetes involves measuring the rate of removal of sugar from the blood, that is, the glucose-tolerance test. One characteristic of aging is a reduction in the rate of removal of excess sugar from the blood. At present it is not known whether this represents the early stages of diabetes or whether it is a normal age change. It does appear in aged individuals who do not show any of the other symptoms of diabetes. Furthermore, it has been shown that, unlike the diabetic, elderly subjects can, with additional stimulation, produce more insulin. In normal young persons, the pancreas releases more insulin in response to even a slight rise in blood sugar levels. In the elderly, the sensitivity of the pancreas is reduced so that a higher level of blood sugar is required to stimulate it to action. With maximum stimulation the pancreas in the aged can produce as much insulin as the pancreas in the young.

It has long been known that the excretion of both male and female sex hormones diminishes with age. In the female, sex hormones falls markedly in menopause . In the male, the excretion of male sex hormones and their degradation products falls gradually over the age span 50–90. A marked reduction in sexual activity is obvious; this diminishes progressively between the ages of 20 and 60 in both males and females. In males the frequency of marital intercourse falls from an average of four per week in 20-year-olds to one per week in 60-year-olds. Practically all males aged 20–45 reported some level of sexual activity. There is usually sexual behavior in individuals over the age of 60, but clinical reports indicate that at least some males remain sexually active at 90.
Bone system [skeletal ].

With ageing, the bones gradually lose calcium. As a result they become more fragile and are more likely to break, even with minor falls. Healing of fractures is also slower in the old than in the young. Recent advances in orthopedic surgery, with the replacement of parts of a broken bone or joint with new structures or the introduction of metallic pegs to hold broken parts together, have been of great value to elderly people. The incidence of osteoporosis, a disease characterized by a loss of calcium and minerals from bone, also increases with age. It occurs more frequently in women after menopause than in men and is especially evident in the spinal column. Back pain is a primary symptom of the disease. It can be treated by increasing calcium intake in association with the administration of anabolic hormones. The mobility of joints diminishes with age and the incidence of arthritis increases.

Taste and smell
After the age of 70 other sense organs may show a reduction in sensitivity. Reduced taste sensitivity is associated with atrophy and loss of taste buds from the tongue in the elderly. The effect of aging on the sense of smell has not been precisely determined because this sense is extremely difficult to assess quantitatively; in addition, smoking and exposure to occupational odors and noxious substances in the air influence sensitivity to smells.
The main focus for most people that are advanced in age is that, think and live like a young person at heart. This coupled with healthy diet; moderate regular exercises would take you a long way.