📝 Chapter Notes & Revision
Human Health and Diseases
📐 Formula & Cheat Sheet (English)
MP Board Class 12 Biology: Quick Revision Notes
Chapter 8: Human Health and Diseases (मानव स्वास्थ्य और रोग)
1. Basic Concepts of Health and Disease
- Health (स्वास्थ्य): A state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity (WHO definition).
- Disease (रोग): Any condition that impairs the normal functioning of the body or its parts.
- Infectious Diseases (संक्रामक रोग): Transmitted from one person to another (e.g., Typhoid, AIDS).
- Non-infectious Diseases (असंक्रामक रोग): Not transmitted from person to person (e.g., Cancer, Diabetes).
2. Common Infectious Diseases in Humans
| Disease | Pathogen (रोगजनक) | Target Organ / Site | Key Symptoms | Diagnostic Test / Vector |
|---|---|---|---|---|
| Typhoid | Salmonella typhi (Bacteria) | Small intestine | High fever ($39^\circ\text{C}$–$40^\circ\text{C}$), stomach pain, constipation, loss of appetite | Widal Test |
| Pneumonia | Streptococcus pneumoniae | Alveoli of lungs | Fever, chills, cough, gray/bluish lips and fingernails | Transmitted via droplets/aerosols |
| Common Cold | Rhinovirus | Nose and respiratory passage (NOT lungs) | Nasal congestion, sore throat, cough, headache (lasts 3–7 days) | Droplets from cough/sneeze |
| Malaria | Plasmodium (P. vivax, P. falciparum, P. malariae) | Liver cells & RBCs | Chills, high recurring fever every 3–4 days | Vector: Female Anopheles mosquito |
| Amoebiasis | Entamoeba histolytica (Protozoa) | Large intestine | Constipation, abdominal pain, stools with excess mucus and blood clots | Vector: Houseflies |
| Ascariasis | Ascaris lumbricoides (Helminth) | Intestine | Internal bleeding, muscular pain, fever, anemia, blockage of intestinal passage | Contaminated water/vegetables |
| Filariasis / Elephantiasis | Wuchereria bancrofti & W. malayi | Lymphatic vessels (usually lower limbs) | Chronic inflammation, swelling of lower limbs and genital organs | Vector: Female Culex mosquito |
| Ringworm | Microsporum, Trichophyton, Epidermophyton (Fungi) | Skin, nails, scalp | Dry, scaly lesions on skin with intense itching | Spread through towels, clothes, or comb |
3. Life Cycle of Malaria (Plasmodium)
- Infective stage to humans: Sporozoites (injected by Female Anopheles mosquito bite).
- Liver Stage: Sporozoites reach liver via blood $\rightarrow$ reproduce asexually $\rightarrow$ burst liver cells.
- RBC Stage: Parasite attacks RBCs $\rightarrow$ reproduces asexually $\rightarrow$ bursts RBCs, releasing a toxic substance called Hemozoin (causes chill and high recurring fever).
- Sexual Stage: Sexual stages (Gametocytes) develop in RBCs.
- Vector Stage: Mosquito bites infected person $\rightarrow$ takes up gametocytes $\rightarrow$ Fertilization occurs in mosquito's gut $\rightarrow$ Sporozoites migrate to salivary glands.
4. Immunity (प्रतिरक्षा)
Immunity is the overall ability of the host to fight disease-causing organisms.
A. Innate Immunity (सहज प्रतिरक्षा)
- Non-specific, present from birth.
- Four Types of Barriers:
- Physical Barriers: Skin, Mucus coating of respiratory, gastrointestinal, and urogenital tracts.
- Physiological Barriers: Acid in stomach, Saliva in mouth, Tears from eyes (contain Lysozyme).
- Cellular Barriers: Leukocytes (WBCs) like Neutrophils (PMNL), Monocytes, Natural Killer (NK) cells, Macrophages.
- Cytokine Barriers: Virus-infected cells secrete proteins called Interferons (protect non-infected cells).
B. Acquired Immunity (उपार्जित प्रतिरक्षा)
- Pathogen-specific, characterized by Memory.
- Primary Response: Low intensity during first encounter with a pathogen.
- Secondary (Anamnestic) Response: High intensity during subsequent encounters.
Types of Immune Responses:
- Humoral Immune Response (AMI): Antibody-mediated; controlled by B-lymphocytes.
- Cell-Mediated Immunity (CMI): Controlled by T-lymphocytes.
- Note: CMI is responsible for graft rejection in organ transplants.
Active vs. Passive Immunity:
| Feature | Active Immunity (सक्रिय प्रतिरक्षा) | Passive Immunity (अक्रिय प्रतिरक्षा) |
|---|---|---|
| Definition | Antibodies produced by host's own body in response to antigens. | Readymade antibodies are directly injected into the host. |
| Speed | Slow, takes time to give full response. | Fast, gives immediate protection. |
| Duration | Long-lasting (memory cells produced). | Short-lived. |
| Example | Natural infection OR Vaccination (e.g., Polio vaccine). | Colostrum (IgA in mother's milk), Anti-tetanus serum (ATS), Snake antivenom. |
5. Structure of an Antibody (प्रतिरक्षी की संरचना)
- An antibody molecule consists of 4 peptide chains:
- 2 Light Chains (small)
- 2 Heavy Chains (large)
- Formula Representation: $H_2L_2$
- Types of Antibodies:
- IgA: Present in Colostrum (mother's milk) and secretions.
- IgE: Involved in Allergies.
- IgG: Most abundant; can cross the placenta.
- IgM: First antibody produced during immune response (largest).
- IgD: B-cell receptor component.
6. Allergies & Autoimmunity
- Allergy (एलर्जी): Exaggerated response of the immune system to certain antigens present in the environment (Allergens like pollen, dust mites, animal dander).
- Antibody involved: IgE.
- Chemicals released: Histamine and Serotonin from Mast cells.
- Treatment: Anti-histamines, Adrenaline, and Steroids.
- Autoimmunity (स्व-प्रतिरक्षा): Abnormal immune response where the body attacks its own self-cells/tissues.
- Example: Rheumatoid Arthritis (गठिया).
7. Immune System in the Body (Lymphoid Organs)
- Primary Lymphoid Organs: Where lymphocytes originate, mature, and differentiate.
- Bone Marrow: Site where all blood cells including lymphocytes are formed.
- Thymus: Site of T-lymphocyte maturation (shrinks in size with age).
- Secondary Lymphoid Organs: Sites where lymphocytes interact with antigens and proliferate.
- Spleen: Large reservoir of erythrocytes (RBC graveyard); filters blood.
- Lymph Nodes: Trap micro-organisms present in lymph/tissue fluid.
- MALT (Mucosa-Associated Lymphoid Tissue): Lines respiratory, digestive, and urogenital tracts; constitutes 50% of lymphoid tissue in human body.
8. AIDS (Acquired Immuno Deficiency Syndrome)
- Causative Agent: HIV (Human Immunodeficiency Virus) – a Retrovirus (enclosed with single-stranded RNA genome).
- Transmission:
- Sexual contact with an infected person.
- Transfusion of contaminated blood.
- Sharing infected needles.
- From infected mother to child through placenta.
- Mechanism of Action:
- HIV enters Macrophages / Helper T-cells ($T_H$ cells).
- Viral RNA replicates to form viral DNA using enzyme Reverse Transcriptase.
- Viral DNA integrates into host cell genome $\rightarrow$ produces more virus particles.
- $T_H$ cell count drops significantly $\rightarrow$ person becomes immune-deficient.
- Diagnosis: ELISA (Enzyme-Linked Immunosorbent Assay).
- Confirmation Test: Western Blot Test.
- Prevention: NACO (National AIDS Control Organisation) and WHO awareness programs.
9. Cancer (कैंसर)
- Characterized by uncontrolled cell division and loss of Contact Inhibition (normal property where contact with other cells inhibits uncontrolled growth).
Types of Tumors:
- Benign Tumor: Remains confined to its original location; non-cancerous.
- Malignant Tumor: Mass of proliferating cells (neoplastic cells) that invade surrounding tissues.
- Metastasis: Property where cancer cells slough off from primary tumor, travel via blood, and start new tumors in distant organs (Most feared property of malignant tumors).
Causes (Carcinogens):
- Physical: UV rays, X-rays, Gamma rays.
- Chemical: Tobacco smoke (causes lung cancer).
- Biological: Oncogenic viruses (contain viral oncogenes). Normal cellular genes called Proto-oncogenes can get activated to oncogenes under certain conditions.
Detection & Diagnosis:
- Biopsy and Histopathological studies.
- Radiography (X-rays), CT (Computed Tomography), MRI (Magnetic Resonance Imaging).
- Use of antibodies against cancer-specific antigens.
Treatment:
- Surgery, Radiation therapy, Chemotherapy (Side effects: hair loss, anemia).
- Immunotherapy: Patients are given $\alpha$-interferon (biological response modifier) to activate their immune system.
10. Drugs and Alcohol Abuse
| Drug Class | Source / Origin | Target Receptors / Organs | Effects & Examples |
|---|---|---|---|
| Opioids | Latex of Papaver somniferum (Poppy plant) | Central Nervous System (CNS) & Gastrointestinal tract | Depressant, slows down body functions. <br> Example: Morphine (painkiller), Heroin (Smack - diacetylmorphine). |
| Cannabinoids | Inflorescence of Cannabis sativa | Brain receptors | Affects cardiovascular system. <br> Example: Marijuana, Hashish, Charas, Ganja. |
| Cocaine (Coca alkaloid) | Erythroxylum coca | Interferes with transport of Dopamine | Stimulates CNS, causes euphoria, hallucinations in high doses. Also called Coke or Crack. |
| Hallucinogens | Plants like Atropa belladonna, Datura, LSD (Claviceps) | Brain | Alters perception, causes vivid hallucinations. |
Key Terms:
- Addiction (व्यसन): Psychological attachment to certain effects (like euphoria) of drugs/alcohol.
- Dependence: Tendency of the body to manifest characteristic Withdrawal Syndrome (anxiety, shakiness, nausea, sweating) if regular dose is abruptly discontinued.
- Cirrhosis: Severe liver damage caused by chronic alcohol consumption.
💡 Top Board Exam Tips for Chapter 8
- Frequently Asked Diagrams:
- Structure of an Antibody molecule ($H_2L_2$).
- Replication cycle of Retrovirus (HIV).
- Life Cycle of Plasmodium.
- High-Yield Distinctions:
- Innate vs. Acquired Immunity.
- Active vs. Passive Immunity.
- Benign vs. Malignant Tumors.
- B-lymphocytes vs. T-lymphocytes.
- One-Marker Focus:
- Diagnostic test for Typhoid: Widal test.
- Diagnostic test for AIDS: ELISA.
- Toxic substance causing malarial chills: Hemozoin.
- Antibody present in Colostrum: IgA.
- Antibody in allergic response: IgE.