Health
According to the World Health Organization (WHO), health is defined as “a state of complete physical, social and mental well-being, and not merely the absence of disease or infirmly”. There is some biological knowledge of some factors affecting physical health, they are the diet, exercise, rest, alcohol abuse, some non-infectious diseases, smoking.
Diet
As heterotrophs we depend on the food we take in as the source of the chemical constituents required for the normal growth and functioning of the body. Deficiency in particular constituent will upset the normal functioning or growth of the body. Also, taking too much energy-rich food will result in problems like overweight or obesity because excess carbohydrates and fats taken in will be stored inside our body as fats.
Exercise
The amount of work the muscles can perform is limited by the amount of oxygen obtained during ventilation, and the efficiency of the cardiovascular system in supplying oxygen to the muscles. As the body is trained to be more efficient in obtaining oxygen and delivering it to the muscles, people who exercise regularly are able to accomplish regular activities casier and respond more readily to sudden demand on physical activities.
The skeletal muscles increase in size, strength and capacity for work with regular and moderate exercise. The muscles involved in ventilation become stringer and thus the vital capacity of the individual is increased. The heart muscle increases in size in response to training. The heart can beat stronger to increase the cardiac output. With an efficient supply of oxygen, the high energy yields from aerobic respiration fuel the muscles to do work.
Rest
Continual activity for a sustained period leads to accumulation of toxic wastes and depletion of food reserve. Therefore, having enough rest is very important to us that allows exhausted cells to undergo a period of inactivity or low activity for moving toxic wastes and replenished the food reserve in the cells.
Alcohol
abuse
Alcohol is a depressant which slows down the activities of the central nervous system. Alcohol slows down the speed at which nerve impulses are transmitted. This lengthens the reaction time of the effected person making him slow to respond. The ability of an individual to reason, to make judgment, and to co-ordinate is reduced as alcohol depresses the activity of the parts of the cerebrum controlling these functions.
Drinking large amounts of alcohol over a long period of time can cause health problems such as malnutrition and hardening of the liver. Malnutrition may result in long-lasting alcoholism because alcoholic beverages are high in caloric content but low in nutritive value. Hardening of the liver is associated with alcohol abuse. Alcohol is mainly metabolized in the lover. The mechanism by which the hardening develops is still unclear, but it appears to involve the consequences of the metabolism of excessive amounts of alcohol.
The
non-infectious diseases
Some diseases cannot be spread. The non-infectious diseases include cancers, stroke and diabetes.
Cancers is not a single disease with a single cause and a single type of treatment. Cancer is a non-transmissible disease characterized by uncontrolled and disordered cell division. Cells normally divide in an orderly and controlled manner. But when the control signals in a normal cell go wrong, the cell will continue to divide, forming a mass of abnormal cells, which is known as tumors. All cancer cells contain abnormal genetic material involving the uncontrolled growth of cells. The normal control of the mitotic cell cycle is ruined in a cancerous cell.
Blood is circulated around the body to supply oxygen and nutrients to the various parts. A disruption of the circulation to vital organs due to narrowing of the blood vessels or clots results in disease such as coronary heart disease and stroke. The affected organ will be deprived of oxygen and nutrient supply.
Diabetes is a result of the failure in the regulation of blood glucose level, it is a chronic disease. When a person is deficient in insulin or when the target cells fail to respond to insulin, the regulation of blood glucose level is upset. It is believed that both genetic and environmental factors such as obesity and lack of exercise are involved.
Genetic diseases are results of mutation at the gene or chromosome level.
Some factors are known to associate closely with certain non-infectious diseases. We should be aware of the following factors.
1. Carcinogens, ionizing radiation, and ultra-violet radiation may cause mutation in the somatic cells or activate genes that are not normally expressed. The control of the normal mitotic cell cycle is ruined the affected cell becomes cancerous.
2. Diet. Chronic overeating of carbohydrate food causes repeated stimulation of the pancreas. The pancreas responds by secreting large quantities of insulin. Repeated exposure of the target cells to large quantities of insulin diminishes the target cells’ responsiveness to the hormones. The target cells then fail to dispose of excess glucose in the usual way. This is thought to induce non-insulin-dependent diabetes. Also, a high level of fat, especially cholesterol, in the blood is a major cause of narrowing of the arteries. The accumulation of cholesterol rich fatty deposits within the walls of the arteries narrows or blocks the blood supply. This explains the high correlation between diet in rich in carbohydrate and fat content and incidence of coronary heart disease and stroke.
3. Smoking. Substances in tar of tobacco smoke are carcinogenic. The risk of developing lung cancer is directly related to the amount of tar that gets into the lungs. It is estimated that about a quarter of the deaths from coronary heart disease were associated with smoking. Nicotine and carbon monoxide in tobacco smoke are thought to be the major causes. Nicotine increases the workload of the heart, while carbon monoxide reduces the supply of oxygen to the heart. Both nicotine and carbon monoxide increase the tendency to develop blood clots within the blood vessels.
6S Sam Leung