The chapter Human Health and Diseases is crucial for both board exams and competitive entrance tests like NEET. It covers a wide range of topics from common infectious diseases and immunity to serious issues like Cancer, AIDS, and Drug Abuse. Below is a comprehensive collection of high-yield questions and detailed answers designed to help you master this chapter.
Topic 1: Common Human Diseases (Pathogens and Control)
Q1. Explain the life cycle of Plasmodium (Malarial Parasite) in the human body.
Answer: The life cycle of Plasmodium requires two hosts: Human and Female Anopheles mosquito. The cycle in humans involves:
- Infection: The infective stage, Sporozoites, enters the human body through the bite of an infected female Anopheles mosquito.
- Liver Stage: The parasites reach the liver through blood and multiply asexually within liver cells, bursting them to release parasites into the blood.
- RBC Stage: They enter Red Blood Cells (RBCs) and reproduce asexually, causing the RBCs to burst. The rupture of RBCs releases a toxic substance called Haemozoin, which is responsible for the chill and high fever recurring every 3-4 days.
- Gametocytes: Some parasites differentiate into sexual stages (male and female gametocytes) in RBCs. These are then picked up by a mosquito during a blood meal to complete the cycle in the mosquito (fertilization and development take place in the mosquito's gut).
Q2. Differentiate between the causative agents and symptoms of Typhoid and Pneumonia.
Answer:
- Typhoid:
- Pathogen: Salmonella typhi (Bacteria).
- Mode of Transmission: Contaminated food and water.
- Site of Infection: Small intestine, then migrates to other organs via blood.
- Symptoms: Sustained high fever (39°–40°C), stomach pain, constipation, headache, and loss of appetite. In severe cases, intestinal perforation and death may occur.
- Diagnosis: Widal Test.
- Pneumonia:
- Pathogen: Streptococcus pneumoniae and Haemophilus influenzae.
- Site of Infection: Alveoli (air-filled sacs) of the lungs.
- Symptoms: The alveoli get filled with fluid leading to severe problems in respiration. Fever, chills, cough, and headache. In severe cases, lips and fingernails may turn gray to bluish.
Q3. Describe the pathogenicity and control of Ascariasis and Filariasis.
Answer:
- Ascariasis:
- Pathogen: Ascaris lumbricoides (Roundworm).
- Symptoms: Internal bleeding, muscular pain, fever, anemia, and blockage of the intestinal passage.
- Transmission: Eggs of the parasite are excreted with the feces of infected persons, contaminating soil, water, and plants. Infection occurs through contaminated vegetables, fruits, and water.
- Filariasis (Elephantiasis):
- Pathogen: Wuchereria bancrofti and Wuchereria malayi (Filarial worms).
- Symptoms: Slowly developing chronic inflammation of the organs in which they live for many years, usually the lymphatic vessels of the lower limbs. It causes gross deformities (Elephantiasis). Genital organs are also often affected.
- Transmission: Transmitted by the bite of female Culex mosquito vectors.
Q4. Write a brief note on viral diseases: Dengue, Chikungunya, and Common Cold.
Answer:
- Common Cold: Caused by Rhinoviruses. They infect the nose and respiratory passage but not the lungs. Symptoms include nasal congestion, discharge, sore throat, and cough. Spread by droplets from cough/sneeze or contaminated objects.
- Dengue: Caused by Flavivirus, transmitted by Aedes aegypti mosquito. Symptoms include high fever, severe headache, pain behind eyes, and muscle/joint pain ("breakbone fever"). Platelet count decreases significantly.
- Chikungunya: Caused by Chikungunya virus, transmitted by Aedes aegypti and Aedes albopictus. Characterized by sudden fever and severe joint pain (arthralgia) which is often debilitating.
Q5. Compare Amoebiasis and Ringworm.
Answer:
- Amoebiasis (Amoebic Dysentery): Caused by the protozoan Entamoeba histolytica in the large intestine. Houseflies act as mechanical carriers. Symptoms include constipation, abdominal pain, cramps, and stools with excess mucous and blood clots.
- Ringworm: Caused by fungi belonging to genera Microsporum, Trichophyton, and Epidermophyton. Symptoms include appearance of dry, scaly lesions on skin, nails, and scalp accompanied by intense itching. Heat and moisture help these fungi grow.
Topic 2: Basic Concepts of Immunology
Q6. Differentiate between Innate and Acquired Immunity.
Answer:
- Innate Immunity: It is non-specific defense present at the time of birth. It consists of four types of barriers:
- Physical: Skin, Mucous coating.
- Physiological: Acid in stomach, Tears from eyes, Saliva.
- Cellular: PMNL-neutrophils, Monocytes, Macrophages.
- Cytokine: Interferons (protect non-infected cells from viral infection).
- Acquired Immunity: It is pathogen-specific and characterized by memory. It is developed during the lifetime. It involves a primary response (low intensity) and a secondary/anamnestic response (high intensity) mediated by B-lymphocytes and T-lymphocytes.
Q7. Explain the structure of an Antibody molecule.
Answer: Each antibody molecule has four peptide chains: two small called light chains and two longer called heavy chains. Hence, an antibody is represented as H2L2. These chains are held together by disulfide bonds. The different types of antibodies are IgA, IgM, IgE, IgG, etc. Antibodies produce the Humoral Immune Response.
Q8. What is the principle of Vaccination and Immunization?
Answer: The principle is based on the property of 'memory' of the immune system. In vaccination, a preparation of antigenic proteins of pathogen or inactivated/weakened pathogen (vaccine) is introduced into the body. The antibodies produced neutralize the pathogenic agents. The vaccines also generate memory B and T-cells that recognize the pathogen quickly on subsequent exposure and overwhelm the invaders with a massive production of antibodies.
Topic 3: HIV, AIDS and Cancer
Q9. Explain the mechanism of HIV infection and how it leads to AIDS.
Answer:
- Virus: HIV (Human Immunodeficiency Virus) is a retrovirus (RNA genome).
- Mechanism: After entering the body, the virus enters macrophages where its RNA genome replicates to form viral DNA with the help of the enzyme Reverse Transcriptase.
- The viral DNA gets incorporated into the host cell's DNA and directs the infected cells to produce virus particles. The macrophages continue to produce virus and act as an "HIV factory".
- Simultaneously, HIV enters Helper T-lymphocytes (TH), replicates, and produces progeny viruses. These destroy the TH cells.
- Result: A progressive decrease in the number of Helper T-lymphocytes leads to a weakened immune system, making the person susceptible to infections (like Mycobacterium, fungi) that a healthy person would overcome.
Q10. What is Cancer? Differentiate between Benign and Malignant tumors.
Answer: Cancer is an uncontrolled division of cells due to the breakdown of regulatory mechanisms like contact inhibition. Cancerous cells form masses of tissue called tumors.
- Benign Tumors: Normally remain confined to their original location and do not spread to other parts of the body. They cause little damage.
- Malignant Tumors: These are masses of proliferating cells called neoplastic cells. They grow very rapidly, invading and damaging surrounding normal tissues. The most feared property is Metastasis, where cells slough off from the tumor, reach distant sites through blood, and start a new tumor there.
Topic 4: Adolescence - Drug and Alcohol Abuse
Q11. Classify the commonly abused drugs with their sources and effects.
Answer:
- Opioids:
- Source: Latex of poppy plant Papaver somniferum.
- Examples: Morphine, Heroin (Smack - chemically diacetylmorphine).
- Effect: Bind to opioid receptors in the CNS and GI tract. Heroin is a depressant and slows down body functions.
- Cannabinoids:
- Source: Inflorescences of the plant Cannabis sativa.
- Examples: Marijuana, hashish, charas, ganja.
- Effect: Affect the cardiovascular system of the body.
- Coca Alkaloids (Cocaine):
- Source: Erythroxylum coca (South America).
- Effect: Interferes with the transport of the neurotransmitter dopamine. It has a potent stimulating action on the CNS, producing a sense of euphoria and increased energy. Excessive dosage causes hallucinations.
Very Short Answer Type Questions (VSAQ) - 1 Mark
Q1. Name the diagnostic test for Typhoid.
Ans. Widal Test.
Q2. Which vector spreads Dengue and Chikungunya?
Ans. Aedes mosquito.
Q3. What is the infectious stage of Plasmodium for humans?
Ans. Sporozoite.
Q4. Name the toxic substance responsible for chills in Malaria.
Ans. Haemozoin.
Q5. Which fungi cause Ringworm?
Ans. Microsporum, Trichophyton, and Epidermophyton.
Q6. Name the vector for Filariasis.
Ans. Female Culex mosquito.
Q7. Which antibody is most abundant in Colostrum (mother's milk)?
Ans. IgA.
Q8. What does PMNL stand for?
Ans. Polymorpho-Nuclear Leukocytes (Neutrophils).
Q9. Which cells are responsible for Cell-Mediated Immunity (CMI)?
Ans. T-lymphocytes.
Q10. Name a protein secreted by virus-infected cells to protect non-infected cells.
Ans. Interferons.
Q11. What is the full form of ELISA?
Ans. Enzyme-Linked Immunosorbent Assay.
Q12. What is Metastasis?
Ans. The property of malignant tumor cells to spread to different parts of the body and form new tumors.
Q13. Name the chemical carcinogen present in tobacco smoke.
Ans. Nicotine and Tar (causes lung cancer).
Q14. Which enzyme is used by HIV to form DNA from RNA?
Ans. Reverse Transcriptase.
Q15. Which cells are primarily attacked by HIV?
Ans. Helper T-lymphocytes (TH cells).
Q16. What is the chemical name of Heroin?
Ans. Diacetylmorphine.
Q17. Which plant yields Cocaine?
Ans. Erythroxylum coca.
Q18. Name a hallucinogenic plant other than Coca.
Ans. Atropa belladonna or Datura.
Q19. What is Cirrhosis?
Ans. Chronic damage to the liver caused by excessive alcohol intake.
Q20. What is MALT?
Ans. Mucosa-Associated Lymphoid Tissue.
Q21. Which fish is used to control mosquito larvae?
Ans. Gambusia.
Q22. Name the pathogen causing Amoebiasis.
Ans. Entamoeba histolytica.
Q23. Identify the antibody involved in allergic reactions.
Ans. IgE.
Q24. Give an example of an Autoimmune Disease.
Ans. Rheumatoid Arthritis.
Q25. Where do T-lymphocytes mature?
Ans. Thymus.
Q26. Which organ is known as the 'graveyard of RBCs'?
Ans. Spleen.
Q27. Name the group of viruses that cause Common Cold.
Ans. Rhinoviruses.
Q28. What is the "Withdrawal Syndrome"?
Ans. The anxiety, shakiness, nausea, and sweating experienced when a regular dose of drug/alcohol is abruptly stopped.
Q29. Which lymphoid organ atrophies with age?
Ans. Thymus.
Q30. Name the causative agent of Pneumonia.
Ans. Streptococcus pneumoniae.
Short Answer Type Questions (SAQ) - 2 to 3 Marks
Q1. Explain the term 'Contact Inhibition'.
Ans. Normal cells show contact inhibition, meaning when they come in contact with other cells, their uncontrolled growth is inhibited. Cancer cells lose this property, leading to tumor formation.
Q2. Differentiate between Primary and Secondary Immune Response.
Ans. Primary response occurs when the body encounters a pathogen for the first time; it is of low intensity. Secondary response occurs upon subsequent encounter with the same pathogen; it is highly intensified due to immune memory.
Q3. Why is mother's milk considered essential for a newborn infant?
Ans. The yellowish fluid colostrum secreted by the mother during the initial days of lactation contains abundant antibodies (IgA) which provide passive immunity to the infant.
Q4. Differentiate between Active and Passive Immunity.
Ans. Active immunity is developed when the host produces antibodies after exposure to antigens (slow, long-lasting). Passive immunity is conferred when ready-made antibodies are directly given to protect the body (fast, short-lived, e.g., anti-tetanus serum).
Q5. What are the symptoms of Ascariasis?
Ans. Internal bleeding, muscular pain, fever, anemia, and blockage of the intestinal passage.
Q6. How does smoking affect the respiratory system?
Ans. Smoking increases Carbon Monoxide (CO) content in blood and reduces Heme-bound oxygen, causing oxygen deficiency. It destroys alveoli walls leading to Emphysema.
Q7. What is the function of the Spleen?
Ans. The spleen acts as a filter of the blood by trapping blood-borne microorganisms. It is also a large reservoir of erythrocytes.
Q8. Explain the biological control of Malaria.
Ans. Introducing larvivorous fishes like Gambusia in ponds feeds on mosquito larvae. Avoiding stagnation of water prevents mosquito breeding.
Q9. What causes Swelling and Redness in Allergy?
Ans. The release of chemicals like histamine and serotonin from mast cells in response to allergens causes dilation of blood vessels and inflammation.
Q10. What is Autoimmunity?
Ans. Sometimes, due to genetic or other unknown reasons, the body attacks self-cells. This results in damage to the body and is called auto-immune disease (e.g., Rheumatoid arthritis).
Q11. Why are cannabinoids banned in sports?
Ans. Cannabinoids are abused by some sportspersons to enhance performance and endurance artificially, which is unethical and harmful to health.
Q12. What are the side effects of anabolic steroids in females?
Ans. Masculinization, increased aggressiveness, mood swings, depression, abnormal menstrual cycles, excessive hair growth on the face and body, and deepening of voice.
Q13. How does Pneumonia spread?
Ans. It spreads by inhaling droplets/aerosols released by an infected person or by sharing glasses and utensils with an infected person.
Q14. Define 'Vaccine'. Give one example.
Ans. A vaccine is a biological preparation containing weakened or inactivated pathogens or their proteins that provides immunity to a particular disease. Example: Polio vaccine.
Q15. Why does an HIV patient suffer from other minor infections?
Ans. Due to the drastic reduction in the number of Helper T-lymphocytes, the person loses the immunity to fight against common bacteria (like Mycobacterium), viruses, and fungi.
Q16. What is the role of Histamine in the body?
Ans. Histamine is a vasodilator and inflammatory mediator released during allergic reactions, causing symptoms like sneezing, watery eyes, and inflammation.
Q17. Distinguish between B-cells and T-cells.
Ans. B-cells produce antibodies (Humoral Immunity) to fight pathogens in the blood. T-cells do not produce antibodies but help B-cells to produce them and directly attack infected cells (Cell-Mediated Immunity).
Q18. Explain the term 'addiction' in the context of drugs.
Ans. Addiction is a psychological attachment to certain effects – such as euphoria and a temporary feeling of well-being – associated with drugs and alcohol.
Q19. What are Carcinogens? Name two types.
Ans. Physical, chemical, or biological agents that transform normal cells into cancerous neoplastic cells are called carcinogens. Types: Ionizing radiation (X-rays), Chemical (Tobacco smoke).
Q20. What is the significance of MALT?
Ans. It constitutes about 50% of the lymphoid tissue in the human body and is located within the lining of the major tracts (respiratory, digestive, urogenital) to trap microbes.
Q21. How is DNA technology used in cancer treatment?
Ans. Monoclonal antibodies produced using DNA technology are used to target specific cancer antigens. Also, genes can be used to treat genetic susceptibility.
Q22. List two measures for the prevention and control of alcohol and drug abuse among adolescents.
Ans. 1. Avoid undue peer pressure. 2. Education and counselling to face problems and stresses.
Q23. What are Interferons and their role?
Ans. Interferons are cytokine barriers. They are proteins secreted by virus-infected cells which protect non-infected cells from further viral infection.
Q24. Why is the secondary immune response faster?
Ans. Because the body already has memory B and T cells from the first exposure. Upon second exposure, these cells recognize the antigen immediately and produce a massive amount of antibodies.
Q25. What is the difference between Morphine and Heroin?
Ans. Morphine is a natural alkaloid extracted from poppy latex and is a sedative. Heroin is chemically modified morphine (diacetylmorphine), which is more potent, white, odorless, and crystalline.
Q26. What causes Elephantiasis?
Ans. Chronic inflammation of lymphatic vessels caused by the accumulation of filarial worms (Wuchereria), leading to swelling of lower limbs.
Q27. Mention the target organ for the virus causing Jaundice (Hepatitis).
Ans. The liver is the primary target organ for Hepatitis viruses.
Q28. What are 'retroviruses'?
Ans. Viruses that have RNA as their genetic material and use the enzyme reverse transcriptase to synthesize DNA from RNA within the host cell (e.g., HIV).
Q29. How can ringworm infection be prevented?
Ans. By maintaining personal hygiene, keeping skin dry, and avoiding sharing towels, combs, or clothes of infected persons.
Q30. What is the role of lymph nodes?
Ans. Lymph nodes trap microorganisms or other antigens that enter the lymph and tissue fluid. Antigens trapped here activate lymphocytes and cause an immune response.