The important changes are briefly discussed below:

REDUCED CELLULAR METABOLISM: – Studies with experimental animals have shown that there is a decrease in the metabolism of the tissues as a result of ageing. Hence, there is a reduction in the basal metabolic rate.

NERVOUS SYSTEM:  As a result of ageing, the following changes in the nervous system take place:

o   Decrease in reaction time especially when higher centres are involved,

o   Decrease in memory power and rate of learning,

o   Changes in behavior and

o   Dimness of vision.

 SKELETAL SYSTEM AND TEETH: – Demineralization of bone has been observed commonly in aged persons. This condition is known as Osteoporosis. Clinical studies have indicated increased calcium requirements for aged persons. Loss of teeth due to decay of teeth and gum is common in aged person.

 GASTROINTESTINAL TRACK:  Decreased secretion of saliva and decreased ability to digest starch has been observed in old people. Gastric acidity decreases in a large percentage of old people. Peptic, tryptic, amylolytic and lipolytic enzyme activities of the digestive secretions are decreased. Changes in the intestinal mucosa result in decreased absorption of nutrients in old people.

 CARDIOVASCULAR SYSTEM: – Increase in the incidence of atherosclerosis has been observed in old people. Changes in the character of heart muscle and coronary arteries lead to less efficient functioning of the heart.

 RENAL SYSTEM: – Kidney functional tests carried out in old people have indicated a decreased functioning of the kidneys.

 INTEGUMENTAL SYSTEM:-Changes in the appearance of the skin, hair and nails are the most familiar indices of advancing age. Decreased elasticity of the skin has also been observed.

 ENDOCRINE SYSTEM: – Marked changes in the endocrine glands take place as a result of ageing. The activities of several endocrine glands such as thyroid, adrenal cortex and Islets of Langerhans are diminished. These influence to a significant extent the metabolism of the cells. The basal metabolic rate is significantly reduced in old people.