Human Health Disease

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Human Health Disease — Quick Facts

Health is a state of complete physical, mental, and social well-being (WHO definition). Disease is any deviation from normal structure or function, characterised by signs (objectively observed) and symptoms (patient-reported).

Types of Diseases:

Category	Description	Examples
Infectious/Communicable	Caused by pathogens; transmissible	Tuberculosis, AIDS, malaria, typhoid
Non-infectious/Non-communicable	Not transmitted between individuals	Diabetes, cancer, heart disease
Congenital	Present from birth	Down syndrome, phenylketonuria
Degenerative	Tissues/organ function declines with age	Osteoarthritis, Alzheimer’s
Deficiency	Due to nutritional deficiency	Marasmus, kwashiorkor, anaemia
Allergic	Immune-mediated response to allergens	Asthma, hay fever

Common Pathogenic Organisms:

Pathogen	Disease(s)	Vector/Transmission
Virus	AIDS, polio, hepatitis B, measles, COVID-19	Sexual contact, airborne, blood
Bacteria	Tuberculosis, typhoid, cholera, pneumonia	Airborne, water, direct contact
Protozoa	Malaria (Plasmodium), amoebic dysentery	Mosquito vector, contaminated food
Helminth	Ascariasis, tapeworm infection	Soil, undercooked meat
Fungus	Candidiasis, ringworm	Direct contact, opportunistic

⚡ Exam tip: Mycobacterium tuberculosis (causes TB) is identified by acid-fast staining (Ziehl-Neelsen stain) — the bacteria retain carbol fuchsin dye even after acid-alcohol treatment due to mycolic acid in their waxy cell wall.

⚡ NEET frequently tests: HIV destroys CD4+ T-helper cells, leading to immunodeficiency. Diagnosis: ELISA (screening) + Western blot (confirmation).

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Human Health Disease — NEET/JEE Study Guide

Innate Immunity (Non-specific): First line of defence — skin, mucous membranes, secretions (tears, saliva, HCl in stomach). Second line of defence — phagocytes (neutrophils, macrophages), natural killer (NK) cells, inflammatory response (histamine release → vasodilation → redness, heat, swelling, pain), interferons (proteins released by virus-infected cells to warn neighbouring cells), complement proteins.

Adaptive Immunity (Specific):

• Humoral immunity (B-cells): B-cells produce antibodies (immunoglobulins) that neutralise pathogens. Memory B-cells enable faster secondary response.
• Cell-mediated immunity (T-cells): T-helper (CD4+) activate B-cells and macrophages; T-cytotoxic (CD8+) kill infected cells directly. Memory T-cells.

Antibody Structure: Y-shaped molecule with 2 heavy chains + 2 light chains, linked by disulfide bonds. Variable region (tips): Antigen-binding site — unique to each antibody. Constant region (stem): Determines antibody class (IgG, IgA, IgM, IgE, IgD).

Class	Location	Function
IgG	Blood, extracellular fluid	Most abundant; crosses placenta
IgM	Blood	First antibody produced; pentamer
IgA	Saliva, tears, breast milk	Mucosal protection
IgE	Bound to mast cells	Allergic reactions; anti-parasitic
IgD	B-cell surface	B-cell receptor

Vaccination: Active immunisation — weakened/inactivated pathogen or its toxin stimulates immune response without causing disease → memory cells produced. Passive immunisation — pre-formed antibodies injected (e.g., anti-venom, immunoglobulin for hepatitis A exposure).

Antibiotics — How They Work:

• Penicillin, ampicillin: Inhibit bacterial cell wall synthesis (peptidoglycan cross-linking)
• Streptomycin, tetracycline: Inhibit protein synthesis (30S ribosome)
• Chloramphenicol: Inhibits 50S ribosome
• Sulphonamides: Inhibit folic acid synthesis
• Ciprofloxacin (fluoroquinolones): Inhibit DNA gyrase (topoisomerase II)

⚡ Important: Antibiotics do NOT work against viruses. Antiviral drugs (e.g., acyclovir for herpes, oseltamivir for influenza) target viral enzymes.

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Human Health Disease — Comprehensive Notes

Major Human Diseases (NEET-Relevant Detail):

Tuberculosis (Mycobacterium tuberculosis):

• Airborne transmission (droplet infection)
• Symptoms: Chronic cough with sputum, haemoptysis (blood in cough), night sweats, weight loss, fever
• Diagnosis: Chest X-ray, sputum smear microscopy (ZN stain), tuberculin skin test (Mantoux test), TB-PCR
• Treatment: DOTS (Directly Observed Treatment Short-course) — RHE (Rifampicin, Isoniazid, Pyrazinamide, Ethambutol) for 6–8 months
• BCG vaccine (Bacille Calmette-Guérin) — live attenuated M. bovis, provides partial protection

AIDS (Acquired Immunodeficiency Syndrome):

• Caused by HIV (Human Immunodeficiency Virus) — a retrovirus
• HIV has envelope (gp120 glycoprotein binds CD4 on T-helper cells) + 2 copies of RNA genome + reverse transcriptase
• Transmission: Unprotected sexual contact, blood products, mother-to-child (vertical), sharing needles
• HIV destroys CD4+ T-cells → immunodeficiency → opportunistic infections (Pneumocystis jirovecii pneumonia, Kaposi’s sarcoma)
• No cure; antiretroviral therapy (ART) slows progression

Typhoid (Salmonella typhi):

• Water/food-borne (feco-oral route)
• Symptoms: Sustained high fever (step-ladder pattern), rose spots on abdomen, splenomegaly, relative bradycardia
• Diagnosis: Widal test (detects antibodies against O and H antigens), blood/stool culture
• Treatment: Chloramphenicol (historical), ciprofloxacin, azithromycin

Malaria (Plasmodium species):

• Vector-borne: Female Anopheles mosquito
• P. vivax (benign tertian), P. falciparum (malignant tertian — severe, drug-resistant), P. malariae (quartan)
• Parasite lifecycle: Sporozoites in mosquito salivary gland → injected into human skin → liver stage (exo-erythrocytic) → merozoites infect RBCs → erythrocytic cycle
• Symptoms: Cyclic fever (every 48h for P. vivax, 72h for P. malariae), chills, headache, splenomegaly, anaemia
• Diagnosis: Peripheral blood smear (Giemsa stain), rapid antigen test
• Treatment: Chloroquine (P. vivax), artemisinin-based combination therapy (ACT for P. falciparum)

Cancer (NEET focus):

• Uncontrolled cell division (loss of cell cycle control)
• Causes: Oncogenic viruses (HPV → cervical cancer, EBV → Burkitt’s lymphoma), chemicals (carcinogens), radiation, hereditary mutations
• Tumour suppressor genes (p53, Rb) — normally inhibit cell cycle; both alleles must be lost for cancer
• Proto-oncogenes (Ras, Myc) — promote cell cycle; become oncogenes when overexpressed
• Benign tumours: Localised, encapsulated. Malignant tumours: Invasive, metastatic (spread via blood/lymph)
• Treatment: Surgery, chemotherapy (alkylating agents, antimetabolites), radiation therapy, immunotherapy

NEET Pattern Analysis: Human health and disease is a consistently tested area (2–3 questions per year). Focus on: immune system components, differences between innate and adaptive immunity, antibody classes, vaccine types, antibiotic mechanisms, and the life cycles of disease-causing organisms (especially Plasmodium).

⚡ NEET 2023 Qn: Which type of immunity is provided by mother’s milk to the newborn? Answer: Passive immunity (IgA — the most common class in breast milk is secretory IgA, which protects the infant’s gut mucosa).