Health versus diseas

 

Before human disease can be discussed, the meanings of the terms health, physical fitness, illness, and disease must be considered. Health could be defined theoretically in terms of certain measured values; for example, a person having normal body temperature, pulse and breathing rates, blood pressure, height,

 weight, acuity of vision, sensitivity of hearing, and other normal measurable

 characteristics might be termed healthy. But what does normal mean, and how is it established? It is well known that if the temperatures are taken of a large number of active, presumably healthy, individuals the temperatures will all come close to 98.6 °F (37 °C). The great preponderance of these values will fall between 98.4 °F (36.9 °C) and 98.8 °F (37.1 °C). Thus, health could in part be defined as having a temperature within this narrow range. Similarly, a normal range can be established for pulse, blood pressure, and height. In some healthy individuals, however, the body temperature may range below 98.4 °F or above 98.8 °F. These low and high temperatures fall outside the limits defined above as normal and are instances of biological variability.

The term physical fitness, although frequently used, is also exceedingly difficult to define. In general it refers to the state of optimal maintenance of muscular strength, proper function of the internal organs, and youthful vigour. The champion athlete prepared to cope not only with the commonplace stresses of life but also with the unusual illustrates the concept of physical fitness. To be in good physical condition is to have the ability to swim a mile to save one’s life or to slog home through snowdrifts when a car breaks down in a storm. Some experts in fitness insist that the state of health requires that the individual be in prime physical condition. They prefer to divide the spectrum of health and disease into (1) health, (2) absence of disease, and (3) disease. In their view, those who are not in prime condition and are not physically fit cannot be considered as healthy merely because they have no disease.

Health involves more than physical fitness, since it also implies mental and emotional well-being. Should the angry, frustrated, emotionally unstable person in excellent physical condition be called healthy? Certainly this individual could not be characterized as effectively functioning in complete harmony with the environment. Indeed, such an individual is incapable of good judgment and rational response. Health, then, is not merely the absence of illness or disease but involves the ability to function in harmony with one’s environment and to meet the usual and sometimes unusual demands of daily life.

Maintenance of health

Health is not a static condition but represents a fluid range of physical and emotional well-being continually subjected to internal and external challenges such as worry, overwork, varying external temperatures, mechanical stresses, and infectious agents. These constantly changing conditions require the adjustment of the function of the various systems within the body. Mechanisms are continually at work to maintain a constant internal environment called by the French scientist Claude Bernard the milieu intérieur. The maintenance of this relatively constant internal environment is known as homeostasis. On a hot summer day, for example, the body is challenged to maintain its normal temperature of 98.6 °F (37 °C). Sweating represents a mechanism by which the skin is kept moist. By the evaporation of the moisture, heat is lost more rapidly. The hot day, therefore, represents a challenge to homeostasis. On a cold day gooseflesh may develop, an example of a homeostatic response that is a throwback to mechanisms in lower animals. In fur-bearing ancestors of humans, cold external environments caused the individual hair shafts to rise and, in effect, produce a heavier, thicker insulation of the body against the external chill. Humans still develop this primitive gooseflesh response but, regrettably, lack the luxuriant pelt to protect themselves.

Metabolic control

In essence, metabolism involves all the physical and chemical processes by which cells are produced and maintained. Included under this broad umbrella are the regulation of fluid and electrolytes, the maintenance of plasma protein levels adequate for the building and repair of cells, and control of the amounts of sugar (glucose) and fats (lipids) in the blood so as to provide sufficient amounts for all the energy-producing activities of the cells.

Disease: signs and symptoms

Disease may be acute, chronic, malignant, or benign. Of these terms, chronic and acute have to do with the duration of a disease, malignant and benign with its potentiality for causing death.

An acute disease process usually begins abruptly and is over soon. Acute appendicitis, for example, is characterized by the sudden onset of nausea, vomiting, and pain usually localized in the lower right side of the abdomen. It usually requires immediate surgical treatment. The term chronic refers to a process that often begins very gradually and then persists over a long period. For example, ulcerative colitis—an inflammatory condition of unknown cause that is limited to the colon—is a chronic disease. Its peak incidence is early in the second decade of life. The disease is characterized by relapsing attacks of bloody diarrhea that persist for weeks to months. These attacks alternate with asymptomatic periods that can last from weeks to years.