🌸Chapter 7
Human Health and Diseases
🔹 INTRODUCTION
Health is a state of complete physical, mental, and
social well-being, not merely the absence of disease or infirmity.
It depends on:
- Genetic constitution
- Environment
- Lifestyle (diet, habits, hygiene)
- Socioeconomic status
🔹 CONCEPT OF DISEASE
Disease
= Disturbance in normal functioning of body organs.
Types:
1.
Infectious
diseases – Caused
by pathogens (bacteria, virus, fungi, protozoa, helminths).
2.
Non-infectious
diseases – Caused
by internal factors (genetic, metabolic, deficiency).
🔹 CAUSES OF DISEASE
|
Type |
Examples |
Mode of Transmission |
|
Bacterial |
Typhoid, Pneumonia |
Contaminated food/water, droplets |
|
Viral |
Common cold, AIDS |
Airborne, sexual contact, blood |
|
Protozoan |
Malaria, Amoebiasis |
Mosquito bite, contaminated food |
|
Helminthic (worm) |
Ascariasis, Filariasis |
Soil, mosquito |
|
Fungal |
Ringworm |
Direct contact |
|
Lifestyle |
Obesity, Diabetes |
Sedentary habits |
🔹 PATHOGENS AND THEIR
EFFECTS
|
Pathogen |
Example Disease |
Major Symptoms |
|
Bacteria |
Typhoid (Salmonella typhi) |
High fever, weakness, intestinal ulcers |
|
Virus |
AIDS (HIV), Common Cold |
Fever, cough, immune suppression |
|
Protozoa |
Malaria (Plasmodium) |
Shivering, fever, anemia |
|
Helminths |
Ascariasis |
Abdominal pain, anemia |
|
Fungi |
Ringworm |
Red circular patches on skin |
🔹 BACTERIAL DISEASES
1️⃣ Typhoid
- Causative agent: Salmonella typhi
- Mode of transmission: Contaminated food & water
- Symptoms: High fever (39–40°C),
weakness, headache, constipation, intestinal perforation (severe cases).
- Diagnosis: Widal test
- Prevention: Proper sanitation, Typhoid
vaccine.
2️⃣ Pneumonia
- Causative agent: Streptococcus pneumoniae
/ Haemophilus influenzae
- Transmission: Droplet infection
- Symptoms: Fever, chills, cough, mucus
with phlegm, breathing difficulty.
- Prevention: Avoid overcrowding, maintain
hygiene, vaccination.
🔹 VIRAL DISEASES
1️⃣ Common Cold
- Causative agent: Rhinovirus
- Mode of infection: Airborne droplets,
contaminated objects.
- Symptoms: Sore throat, nasal congestion,
mild fever, tiredness.
- Duration: 3–7 days.
- Prevention: Personal hygiene, healthy
diet.
2️⃣ AIDS (Acquired ImmunoDeficiency
Syndrome)
- Causative agent: Human Immunodeficiency
Virus (HIV)
- Target: Helper T-cells (CD4+)
of immune system
- Mode of Transmission:
- Unprotected sexual contact
- Blood transfusion
- Sharing infected needles
- Infected mother to child
- Symptoms:
- Weight loss
- Chronic fever and diarrhea
- Opportunistic infections (like
TB, pneumonia)
- Diagnosis: ELISA test
- Prevention:
- Safe sex practices
- Use disposable syringes
- Screened blood transfusion
- ART (Antiretroviral therapy)
helps prolong life
🔹 PROTOZOAN DISEASES
1️⃣ Malaria
- Causative agent: Plasmodium species (P.
vivax, P. falciparum, P. malariae, P. ovale)
- Vector: Female Anopheles mosquito
- Infective form: Sporozoite (in
mosquito’s saliva)
Life Cycle (simplified):
1.
Mosquito
injects sporozoites → liver → multiply → enter RBCs
2.
RBCs
rupture → release toxins → chills & fever
3.
Another
mosquito bites → cycle continues
Symptoms:
- High fever with shivering
- Anemia due to RBC destruction
- Enlarged spleen
Prevention:
- Mosquito nets, repellents
- Use of insecticides
- Anti-malarial drugs (quinine,
chloroquine)
2️⃣ Amoebiasis (Amoebic dysentery)
- Causative agent: Entamoeba histolytica
- Mode: Contaminated food/water
- Symptoms: Abdominal pain, blood and
mucus in stool.
- Prevention: Good sanitation, clean food
& water.
🔹 HELMINTHIC DISEASES
1️⃣ Ascariasis
- Causative agent: Ascaris lumbricoides
- Mode: Eggs in contaminated
food/water
- Symptoms: Abdominal pain, anemia,
malnutrition.
- Prevention: Sanitation, washing fruits
& vegetables properly.
2️⃣ Filariasis (Elephantiasis)
- Causative agent: Wuchereria bancrofti, W.
malayi
- Vector: Culex mosquito
- Symptoms: Chronic inflammation →
swelling of limbs and genitals.
- Prevention: Mosquito control.
🔹 FUNGAL DISEASE
Ringworm
- Causative agent: Microsporum, Trichophyton,
Epidermophyton
- Transmission: Contact with infected person
or objects.
- Symptoms: Dry scaly lesions, intense
itching.
- Prevention: Personal hygiene, avoid
sharing towels/clothes.
🔹 IMMUNITY AND IMMUNE SYSTEM
Immunity = Ability of the body to
resist infection.
Types of Immunity:
1.
Innate
(Natural) — present
by birth
o Non-specific defense
o Includes:
§ Physical barriers (skin, mucous)
§ Physiological barriers (HCl, saliva)
§ Cellular barriers (macrophages, NK
cells)
§ Cytokine barriers (interferons)
2.
Acquired
(Adaptive) —
develops after exposure
o Specific defense
o Has memory
o Two types:
§ Active immunity: Body produces antibodies
(infection/vaccine)
§ Passive immunity: Ready-made antibodies (e.g. mother
to baby, serum injection)
Humoral and Cell-Mediated Immunity
|
Type |
Mediated by |
Example |
|
Humoral |
B-lymphocytes (antibodies in blood) |
Against bacteria/toxins |
|
Cell-mediated |
T-lymphocytes |
Against viruses, cancer cells |
🔹 VACCINATION AND
IMMUNISATION
Vaccine:
A preparation containing dead/weakened pathogens → induces immunity.
Examples:
|
Disease |
Vaccine |
|
Smallpox |
Vaccinia |
|
Polio |
OPV (Sabin), IPV (Salk) |
|
TB |
BCG |
|
Hepatitis B |
Recombinant vaccine |
|
Tetanus |
Toxoid |
🔹 ALLERGIES
- Definition: Hypersensitive reaction of
immune system to certain antigens (called allergens).
- Symptoms: Sneezing, watery eyes, skin
rash, difficulty in breathing.
- Mediators: Histamine and serotonin (from
mast cells).
- Treatment: Antihistamines, steroids.
🔹 AUTOIMMUNE DISEASES
- Body’s immune system attacks
its own cells.
- Examples:
- Rheumatoid arthritis
- Type-1 diabetes
- Myasthenia gravis
🔹 IMMUNODEFICIENCY DISEASES
- When immune system becomes
weak.
- Example: AIDS (due to HIV infection).
🔹 CANCER
Definition: Uncontrolled division of
cells forming a tumor.
Types:
1.
Benign
tumor:
Localized, non-invasive.
2.
Malignant
tumor: Spreads
to other body parts (metastasis).
Causes (Carcinogens):
- Physical: X-rays, UV-rays
- Chemical: Tobacco smoke,
aflatoxin
- Biological: Oncogenic viruses
(e.g., HPV)
Treatment:
- Surgery
- Radiotherapy
- Chemotherapy
- Immunotherapy (using α-interferons)
🔹 DRUGS AND ALCOHOL ABUSE
Commonly Abused Drugs:
|
Category |
Examples |
Effects |
|
Opioids |
Morphine, Heroin (smack) |
Depress brain activity |
|
Coca alkaloids |
Cocaine |
Euphoria, increased alertness |
|
Cannabinoids |
Charas, Ganja, Marijuana |
Alter perception, affect coordination |
|
Hallucinogens |
LSD |
Hallucinations |
Alcohol Abuse:
- Depressant effect on CNS
- Causes liver cirrhosis, heart
diseases, fetal alcohol syndrome (in pregnant women)
Adolescence and Drug Abuse:
- Reasons: curiosity, peer
pressure, stress
- Prevention: counseling, healthy
lifestyle, family support.
🔹 KEY DIAGRAMS (NCERT)
1.
Life
cycle of Plasmodium
2.
Life
cycle of Ascaris
3.
Structure
of HIV
4.
Immune
response (B-cell & T-cell interaction)
🔹 NCERT KEYWORDS (Must
Remember for NEET & Boards)
- Pathogen
- Vector
- Immunity
- Antibody
- Vaccine
- Antigen
- Interferon
- Metastasis
- Allergy
- Autoimmunity
- AIDS
- ELISA test
- Innate / Acquired Immunity
- Active / Passive Immunity
🧠REVISION SHEET (Before
Exam)
|
Concept |
Quick Recall |
|
Health |
Complete physical, mental, social well-being |
|
Typhoid test |
Widal |
|
AIDS virus |
HIV (Retrovirus) |
|
Malaria vector |
Female Anopheles |
|
Filariasis vector |
Culex
mosquito |
|
Innate barriers |
Skin, HCl, tears |
|
Vaccine |
Artificial active immunity |
|
Autoimmune disease |
Rheumatoid arthritis |
|
Cancer spread |
Metastasis |
|
Drug abuse prevention |
Education, counseling, family support |
🌟 EXAM PREPARATION TIPS
🧩 For NEET:
- Focus on causative agents,
vectors, symptoms, and modes of transmission.
- Practice diagrams (HIV,
Plasmodium).
- Revise immunity types
and vaccination chart.
📚 For Boards:
- Write definitions, examples,
and NCERT points clearly.
- Draw neat labeled diagrams.
- Revise NCERT line-by-line
for short-answer questions.
