Chapter 7 HUMAN HEALTH AND DISEASE, NCERT

Human Health and Dideases

1. HUMAN HEALTH AND DISEASE Pooja Singh PGT Biology

2. Define Health 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. Diseases can be broadly grouped into infectious and non-infectious . Diseases which are easily transmitted from one person to another, are called infectious diseases.

3. A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc., could cause diseases in man. Such disease causing organisms are called pathogens .

4. Typhoid 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 Typhoid fever could be confirmed by widal test

5. Pneumonia Streptococcus pneumoniae and Haemophilus influenzae are responsible for the disease in humans which infects the alveoli (air filled sacs) of the lungs. As a result of the infection, the alveoli get filled with fluid leading to severe problems in respiration The symptoms of pneumonia include fever, chills, cough and headache. A healthy person acquires the infection by inhaling the droplets/aerosols released by an infected person or even by sharing glasses and utensils with an infected person.

6. Common cold The disorder is caused by Rhino virus They infect the nose and respiratory passage but not the lungs. The common cold is characterised by nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc., which usually last for 3-7 days. Droplets resulting from cough or sneezes of an infected person are either inhaled directly or transmitted through contaminated objects

7. Malaria Plasmodium, a tiny protozoan is responsible for this disease Different species of Plasmodium ( P. vivax, P. malaria and P. falciparum ) are responsible for different types of malaria. Of these, malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal.

8. Life Cycle of Plasmodium (Malaria Parasite) Infection Begins Plasmodium enters the human body when an infected female Anopheles mosquito bites a person.

9. Sporozoites Enter Blood The mosquito injects sporozoites (infective stage) into the human bloodstream.

10. Liver Stage Sporozoites reach the liver and multiply.

11. RBC Stage From the liver, the parasite enters red blood cells (RBCs) and continues to multiply. Bursting of RBCs Infected RBCs burst, releasing the parasites into the blood. This leads to repeated episodes of fever, which are the symptoms of malaria.

12. Formation of Gametocytes   Some parasites in the RBCs develop into gametocytes (male and female forms). When another female Anopheles mosquito bites the infected person, it takes up gametocytes. In the mosquito's stomach, fertilization occurs, forming a zygote.

13. The zygote develops into new sporozoites, which reach the mosquito's salivary glands. The mosquito transmits sporozoites to another person through a bite, restarting the cycle.

14. Ascariasis- caused by ascaris Symptoms of these disease include internal bleeding, muscular pain, fever, anemia and blockage of the intestinal passage Elephantiasis or Filariasis caused by Wuchereria cause a slowly developing chronic inflammation of the organs in which they live for many years, usually the lymphatic vessels of the lower limbs and the disease The pathogens are transmitted to a healthy person through the bite by the female mosquito vectors.

15. Ringworms Many fungi belonging to the genera Microsporum , Trichophyton and Epidermophyton are responsible for ringworm Appearance of dry, scaly lesions on various parts of the body such as skin, nails and scalp are the main symptoms of the disease. Ringworms are generally acquired from soil or by using towels, clothes or even the comb of infected individuals.

16. IMMUNITY The overall ability of the host to fight the disease-causing organisms, conferred by the immune system is called immunity. Immunity is of two types: Innate immunity Acquired immunity.

17. Innate Immunity Innate immunity is non-specific type of defence , that is present at the time of birth. Innate immunity consist of four types of barriers. Physical barriers : Skin on our body is the main barrier which prevents entry of the micro-organisms. Mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts also help in trapping microbes entering our body. 2. Physiological barriers : Acid in the stomach, saliva in the mouth, tears from eyes–all prevent microbial growth.

18. 3. Cellular barriers : Certain types of leukocytes (WBC) of our body like polymorpho-nuclear leukocytes (PMNL-neutrophils) and monocytes and natural killer (type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes. 4. Cytokine barriers : Virus-infected cells secrete proteins called interferons which protect non-infected cells from further viral infection.

19. Acquired Immunity Acquired immunity is pathogen specific. It is characterised by memory. This means when our body encounters a pathogen for the first time it produces a response called primary response which is of low intensity. Second encounter with the same pathogen elicits a stronger response.

20. The primary and secondary immune responses are carried out with the help of two special types of lymphocytes present in our blood, B-lymphocytes T-lymphocytes.

21. The B-lymphocytes produce an army of proteins in response to pathogens into our blood to fight with them. These proteins are called antibodies . The T-cells themselves do not secrete antibodies but help B cells to produce them.

22. Structure of Antibody Each antibody molecule has four peptide chains, two small called light chains and two longer called heavy chains . Hence, an antibody is represented as H2 L2 . Chains has disulphide ( S-S) linkage

23. Types of antibodies IgA IgM IgE IgD IgG

24. Types of immune response Humoral immune response- given by B Lymphocyte Cell-mediated immune response - by T lymphocytes

25. Why is it that the organs cannot be taken from just anybody? Why tissue matching, blood group matching are essential before undertaking any graft/transplant?

26. Active and Passive Immunity When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity . Active immunity is slow and takes time to give its full effective response. When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity. The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant.

27. Vaccination and Immunisation proteins of pathogen or inactivated/weakened pathogen (vaccine) are introduced into the body. The antibodies produced in the body against these antigens would neutralise the pathogenic agents during actual infection.

28. If a person is infected with some deadly microbes to which quick immune response is required as in tetanus , we need to directly inject the preformed antibodies, or antitoxin Even in cases of snakebites , the injection which is given to the patients, contain preformed antibodies against the snake venom. This type of immunisation is called passive immunisation .

29. Allergies The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The substances to which such an immune response is produced are called allergens The antibodies produced to these are of IgE type . Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.

30. Auto Immunity Autoimmunity is a condition in which the immune system fails to recognize the body’s own cells and tissues as "self" and instead attacks them as if they were foreign invaders (like bacteria or viruses). Example Rheumatoid arthritis

31. Lymphoid organs Lymphoid organs are the specialized tissues where lymphocytes (a type of white blood cell) are formed, matured, and activated to fight infections. The primary lymphoid organs are bone marrow and thymus After maturation the lymphocytes migrate to secondary lymphoid organs like spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix. There is lymphoid tissue also located within the lining of the major tracts (respiratory, digestive and urogenital tracts) called mucosa associated lymphoid tissue (MALT). It constitutes about 50 per cent of the lymphoid tissue in human body

32. AIDS Full form : Acquired Immuno Deficiency Syndrome Not congenital : Acquired during lifetime, not by birth. Syndrome : Group of symptoms. First reported : 1981 → has killed over 25 million people worldwide.

33. Cause Caused by HIV (Human Immunodeficiency Virus) . HIV is a retrovirus with an RNA genome and envelope . Transmission Sexual contact with infected person. Transfusion of contaminated blood/blood products. Sharing infected needles (Drug abusers). Mother → child (through placenta).

34. High-risk groups : People with multiple sexual partners. drug users. Patients needing repeated blood transfusions. Children born to HIV-infected mothers.

35. Infection Process HIV enters macrophages → viral RNA → viral DNA (via reverse transcriptase). Viral DNA integrates into host DNA → produces new viruses. HIV also infects helper T-lymphocytes (TH) . Continuous destruction of helper T-cells → immune system weakens. Symptoms: fever, diarrhoea, weight loss.

36. Diagnosis ELISA test commonly used. Treatment Anti-retroviral drugs : only prolong life, do not cure. Prevention Best strategy as no cure. Safe blood transfusion. Disposable needles/syringes only. Free distribution of condoms. Control of drug abuse. Safe sex practices. Regular HIV testing for high-risk groups.

37. Cancer Definition : Uncontrolled growth of cells due to loss of regulation → forms tumors. Properties Normal cells : Show contact inhibition (stop dividing when in contact with other cells). Cancer cells : Lose contact inhibition → divide continuously → form tumors.

38. Types of Tumors Benign tumors : Localized, do not spread, cause little damage. Malignant tumors : Rapidly growing, invasive, damage normal tissues. Compete for nutrients with normal cells. Spread to distant sites via blood → form new tumors (property = Metastasis ).

39. Causes (Carcinogens) Physical : Ionising radiation (X-rays, gamma rays), non-ionising radiation (UV). Chemical : Tobacco smoke → major cause of lung cancer. Biological : Oncogenic viruses (viral oncogenes), cellular oncogenes (proto-oncogenes) activated abnormally.

40. Treatment Surgery : Removal of tumor . Radiotherapy : Irradiating tumor cells (normal cells protected). Chemotherapy : Anti-cancer drugs (often with side effects: hair loss, anemia ). Immunotherapy : Immune system stimulated. Biological response modifiers (e.g., α- interferon) help destroy tumor . Combination therapy : Surgery + radiotherapy + chemotherapy is most common.

41. Commonly Abused Drugs Opioids Bind to opioid receptors in CNS & gut. Extracted from Papaver somniferum poppy latex Taken by snorting/injection. Effect: Depressant → slows down body functions.

42. Cannabinoids Bind to cannabinoid receptors in brain. Source: Cannabis sativa . Products: Marijuana, hashish, charas , ganja . Taken by inhalation/oral. Affects cardiovascular system.

43. Cocaine (coca alkaloid) From Erythroxylum coca Interferes with dopamine transport. Taken by snorting.