Ch-7: Human Health & Disease

Health: A state of complete physical, mental, and social well-being, not merely the absence of disease. Good health is maintained by balanced diet, personal hygiene, and regular exercise.

Common Infectious Diseases

• 1. Bacterial Diseases:
  • Typhoid: Caused by Salmonella typhi. Enters via contaminated food/water. Symptoms: High fever, weakness, stomach pain. Confirmed by Widal tesst Widal test.
  • Pneumonia: Caused by Streptococcus pneumoniae & Haemophilus influenzae. Infects alveoli of lungs (get filled with fluid). Transmission: Inhaling droplets/aerosols.
• 2. Viral Diseases:
  • Common Cold: Caused by Rhino viruses. Infects nose & respiratory passage but not lungs.
• 3. Protozoan Diseases:
  • Malaria: Caused by Plasmodium (P. vivax, P. malaria, P. falciparum - most dangerous). Transmitted by bite of female Anopheles mosquito (vector). Requires two hosts: human and mosquito.
  • Amoebiasis: Caused by Entamoeba histolytica (large intestine). Vectors: Houseflies. Transmission: contaminated water/food.
• 4. Helminthic Diseases:
  • Ascariasis: Caused by Ascaris (roundworm). Symptoms: internal bleeding, muscular pain. Transmitted via contaminated soil, water, plants.
  • Filariasis: Wuchereria bancrofti. Causes chronic inflammation of lymphatic vessels (Elephantiasis).

* Prevention of water-borne diseases: Proper disposal of waste,
regular cleaning of water reservoirs, standard hygiene practices! *

Immunity

The ability of the host to fight the disease-causing organisms.

• A. Innate Immunity: Non-specific, present at birth. Consists of 4 barriers:
  • 1. Physical: Skin, mucus coating.
  • 2. Physiological: Acid in stomach, saliva, tears.
  • 3. Cellular: Leukocytes (WBCs), Macrophags Macrophages.
  • 4. Cytokine: Virus-infected cells secrete proteins called Interferons.

• B. Acquired Immunity: Pathogen specific, characterized by memory. Mediated by B-lymphocytes (produce antibodies) and T-lymphocytes.

Antibody Structure: Has 4 peptide chains - 2 small (light) and 2 longer (heavy). Represented as H2L2. (e.g., IgA, IgM, IgE, IgG).

Active vs Passive Immunity:
- Active: Host produces antibodies when exposed to antigens (slow process).
- Passive: Ready-made antibodies are directly given (e.g., Colostrum from mother has IgE... wait IgE? NO! It is IgA).

Immune System in the Body

• Primary Lymphoid Organs: Bone marrow & Thymus. (Where immature lymphocytes differentiate into antigen-sensitive lymphocytes).
• Secondary Lymphoid Organs: Spleen, lymph nodes, tonsils, Peyer's patches. (Sites for interaction of lymphocytes with antigen).
  * MALT: Mucosa-Associated Lymphoid Tissue (~50% of lymphoid tissue).

AIDS (Acquired Immuno Deficiency Syndrome)

Caused by HIV (Human Immunodeficiency Virus) - a retrovirus. NACO (National AIDS Control Organisation) works to prevent it.

Transmission: Sexual contact, contaminated blood/needles, infected mother to child.

Mechanism: Virus enters macrophages (acts as HIV factory) → enters Helper T-lymphocytes (TH) → replicates & reduces TH count → severe immunity loss.

Cancer

Normal cells show contact inhibition. Cancerous cells lose this property, dividing uncontrollably to form masses called tumors (Benign or Malignant).

Metastasis: The most feared property where malignant cells spread to distant sites via blood and start new tumors.

Causes: Carcinogens (X-rays, UV rays, tobacco smoke, oncogenic viruses).

Drugs and Alcohol Abuse

• Opioids: Bind to receptors in CNS & GI tract (e.g., Heroin - a depressant).
• Cannabinoids: Affect cardiovascular system (Marijuana, Hashish).
• Coca Alkaloids (Cocaine): Stimulates CNS, producing euphoria.

Repeated use leads to tolerance and addiction. Adolescents are vulnerable due to peer pressure and stress. Prevention: Education, counseling, and seeking professional help!