NCERT Book Class 12 Biology Human Health and Disease

HUMAN HEALTH AND DISEASE

Introduction
Health, for a long time, was considered as a state of body and mind where there was a balance of certain ‘humors’. This is what early Greeks like Hippocrates as well as Indian Ayurveda system of medicine asserted. It was thought that persons with ‘blackbile’ belonged to hot personality and would have fevers. This idea was arrived at by pure reflective thought. The discovery of blood circulation by William Harvey using experimental method and the demonstration of normal body temperature in persons with blackbile using thermometer disproved the ‘good humor’ hypothesis of health. In later years, biology stated that mind influences, through neural system and endocrine system, our immune system and that our immune system maintains our health. Hence, mind and mental state can affect our health. Of course, health is affected by –

(i) genetic disorders – deficiencies with which a child is born and deficiencies/defects which the child inherits from parents from birth;

(ii) infections and

(iii) life style including food and water we take, rest and exercise we give

The term health is very frequently used by everybody. How do we define it? Health does not simply mean ‘absence of disease’ or ‘physical fitness’. It could be defined as a state of complete physical, mental and social well-being. When people are healthy, they are more efficient at work. This increases productivity and brings economic prosperity. Health also increases longevity of people and reduces infant and maternal mortality.

Balanced diet, personal hygiene and regular exercise are very important  to maintain good health. Yoga has been practised since time immemorialto achieve physical and mental health. Awareness about diseases and their effect on different bodily functions, vaccination (immunisation) against infectious diseases, proper disposal of wastes, control of vectors and maintenance of hygienic food and water resources are necessary for achieving good health.

When the functioning of one or more organs or systems of the body is adversely affected, characterised by various signs and symptoms, we say that we are not healthy, i.e., we have a disease. Diseases can be broadly grouped into infectious and non-infectious. Diseases which are easily transmitted from one person to another, are called infectious diseases. Infectious diseases are very common and every one of us suffers from these at sometime or other. Some of the infectious diseases like AIDS are fatal. Among non-infectious diseases, cancer is the major cause of death. Drug and alcohol abuse also affect our health adversely.

8.1 COMMON DISEASES IN HUMANS

A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc., could cause diseases in man. Such diseasecausing organisms are called pathogens. All parasites are therefore pathogens as they cause harm to the host by living in (or on) them. The pathogens can enter our body by various means, multiply and interfere with normal vital activities, resulting in morphological and functional damage. Pathogens have to adapt to life within the environment of the  host. For example, the pathogens that enter the gut must know a way ofsurviving in the stomach at low pH and resisting the various digestive enzymes. A few representative members from different groups of pathogenic organisms are discussed here alongwith the diseases caused by them. Preventive and control measures against these diseases in general, are also briefly described.

Salmonella typhi is a pathogenic bacterium which causes typhoid fever in human beings. These pathogens generally enter the small intestine through food and water contaminated with them and migrate to other organs through blood. Sustained high fever (39° to 40°C), weakness, stomach pain, constipation, headache and loss of appetite are some of the common symptoms of this disease. Intestinal perforation and death may occur in severe cases. Typhoid fever could be confirmed by Widal test. A classic case in medicine, that of Mary Mallon nicknamed Typhoid Mary, is worth mentioning here.

EXERCISES

1. What are the various public health measures, which you would suggest as safeguard against infectious diseases?

2. In which way has the study of biology helped us to control infectious diseases?

3. How does the transmission of each of the following diseases take place?

 (a) Amoebiasis

 (b) Malaria

 (c) Ascariasis

 (d) Pneumonia

4. What measure would you take to prevent water-borne diseases?

5. Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.

6. Name the primary and secondary lymphoid organs.

7. The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form:

 (a) MALT

 (b) CMI

 (c) AIDS

 (d) NACO

 (e) HIV

8. Differentiate the following and give examples of each:

 (a) Innate and acquired immunity

 (b) Active and passive immunity

9. Draw a well-labelled diagram of an antibody molecule.

10. What are the various routes by which transmission of human immunodeficiency virus takes place?

11. What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?

12. How is a cancerous cell different from a normal cell?

13. Explain what is meant by metastasis.

14. List the harmful effects caused by alcohol/drug abuse.

15. Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?

16. Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.

17. In your view what motivates youngsters to take to alcohol or drugs?

Please refer to attached file for NCERT Class 12 Biology Human Health and Disease