Human Health and Diseases NCERT PDF

# CHAPTER 8 ## HUMAN HEALTH AND DISEASE ### 8.1 Common Diseases in Humans - The term health is often used to describe a state of complete physical, mental, and social well-being. - Health is not simply the absence of disease or physical infirmity. - Health is a positive concept emphasizing social a...

# CHAPTER 8 ## HUMAN HEALTH AND DISEASE ### 8.1 Common Diseases in Humans - The term health is often used to describe a state of complete physical, mental, and social well-being. - Health is not simply the absence of disease or physical infirmity. - Health is a positive concept emphasizing social and personal resources as well as physical capabilities. - Health allows people to lead productive lives and contribute to society. - A healthy person is more efficient at work, increases productivity, and brings economic prosperity. - Health also increases a person's longevity and reduces infant and maternal mortality. ### 8.2 Immunity - Immunity is the ability of a host to fight disease-causing organisms. - Two types of immunity exist: - **Innate Immunity:** Non-specific and present at the time of birth. It is accomplished by various barriers that prevent foreign agents from entering the body. - **Physical Barriers:** Skin and mucous membranes act as the first line of defense against pathogens. - **Physiological Barriers:** Acidic pH of the stomach, saliva, and tears all contribute to inhibiting microbial growth. - **Cellular Barriers:** Certain types of leukocytes, including neutrophils, phagocytize and destroy foreign invaders. - **Cytokine Barriers:** Virus-infected cells secrete interferons, which protect non-infected cells from further viral infection. - **Acquired Immunity:** Pathogen-specific and characterized by memory. The body remembers previous encounters with pathogens and mounts a stronger response upon subsequent encounters. - **Primary Response:** This occurs when the body encounters a pathogen for the first time and produces a weak initial immune response. - **Secondary Response:** A much stronger and faster response due to the body's memory of the pathogen, thanks to specialized lymphocytes called B-cells and T-cells. - **Humoral Immunity:** Antibody-mediated response based on the production of antibodies by B-cells. - **Cell-Mediated Immunity:** Mediated by T-cells which directly attack infected cells. - **Active Immunity:** Developed when a host is exposed to antigens, either through natural infection or vaccination. - **Passive Immunity:** Acquired when ready-made antibodies are directly given to protect the body against foreign agents. - **Vaccination and Immunization:** The principle behind this is based on the body's memory of immune response. Vaccines contain weakened or inactivated versions of pathogens, stimulating the immune system to produce antibodies without causing disease. - **Allergies:** Exaggerated responses of the immune system to certain antigens in the environment called allergens. Symptoms include sneezing, runny nose, difficulty breathing, and skin rashes. - **Auto-Immunity:** Occurs when the immune system attacks its own cells, leading to autoimmune diseases like rheumatoid arthritis and diabetes mellitus. - **Immune System in the Body:** Consists of lymphoid organs, tissues, cells, and soluble molecules like antibodies. - **Primary Lymphoid Organs:** Bone marrow and thymus, where lymphocytes are produced and mature. - **Secondary Lymphoid Organs:** Spleen, lymph nodes, tonsils, Peyer's patches, and appendix, where lymphocytes interact with antigens and become effector cells. ### 8.3 AIDS - **Acquired Immune Deficiency Syndrome (AIDS):** A condition of severe immunodeficiency caused by the Human Immunodeficiency Virus (HIV), a retrovirus that attacks the immune system, specifically helper T-lymphocytes. - **HIV Transmission:** Occurs through sexual contact, blood transfusions (from contaminated blood or blood products), sharing infected needles, and from an infected mother to her child during pregnancy or childbirth. - **HIV Progression:** The virus enters macrophages and helper T-lymphocytes, replicates, and produces progeny viruses. The progeny viruses then attack other helper T-lymphocytes, eventually leading to a decline in their numbers. - **AIDS Symptoms:** A decrease in the number of helper T-lymphocytes makes the body susceptible to various infections like pneumonia, tuberculosis, and toxoplasmosis. - **AIDS Diagnosis:** Enzyme-Linked Immunosorbent Assay (ELISA) and Western Blot tests are used to detect HIV antibodies in the blood. - **AIDS Treatment:** No cure exists for AIDS but antiretroviral drugs can prolong the life of the patient. - **AIDS Prevention:** Avoiding high-risk behaviors, practicing safe sex, using sterile needles, and getting tested for HIV regularly. ### 8.4 CANCER - **Cancer:** A disease characterized by uncontrolled cell growth and division. - **Types of Cancer:** Benign (non-cancerous) and malignant (cancerous). - **Causes of Cancer:** Exposure to carcinogens (physical, chemical, or biological agents), oncogenic viruses, and the activation of proto-oncogenes in normal cells. - **Cancer Detection and Diagnosis:** Early detection is crucial. It is done through biopsy, histopathological studies, blood and bone marrow tests, radiography, CT scan, MRI, and specialized antibodies. - **Cancer Treatment:** Surgery, radiation therapy, and immunotherapy are common approaches. ### 8.5 Drugs and Alcohol Abuse - **Drug Abuse:** Using drugs for purposes other than medicinal use. - **Types of Drugs:** Opioids (heroin, morphine), cannabinoids (marijuana, hashish), and coca alkaloids (cocaine). - **Effects of Drugs:** Opioids act as depressants, cannabinoids affect the cardiovascular system, and cocaine acts as a stimulant. - **Sedatives and Tranquilizers:** Drugs that depress brain activity and are often used for treating anxiety and insomnia. - **Stimulants:** Drugs that increase central nervous system activity, such as caffeine and amphetamines. - **Hallucinogens:** Drugs that distort perceptions of reality, such as LSD and marijuana. - **Addiction:** Psychological attachment to a drug's effects, leading to a craving and a compulsion to take it. - **Dependence:** The body develops a tolerance to the drug, requiring higher doses to achieve the same effect. Withdrawal from the drug can cause unpleasant symptoms. - **Adolescence and Drug/Alcohol Abuse:** Curiosity, peer pressure, stress, and a desire for excitement contribute to the problem. - **Effects of Drug/Alcohol Abuse:** Reckless behavior, vandalism, violence, coma, death, and various long-term health consequences. - **Prevention and Control:** Early identification of risk factors, education about the dangers, promoting healthy lifestyles, and providing support for individuals struggling with substance abuse.