Human Health and Disease

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Human Health and Disease Health Definition: A state of complete physical, mental, and social well-being, not merely the absence of disease. Factors Affecting Health: Genetic disorders Infections Lifestyle (food, water, rest, exercise, habits) Maintaining Good Health: Balanced diet Personal hygiene Regular exercise Awareness about diseases & their effects Vaccination (immunisation) Proper disposal of wastes Control of vectors Maintenance of hygiene in food and water resources Disease Classification: Infectious Diseases: Easily transmitted from one person to another (e.g., AIDS). Non-infectious Diseases: Not easily transmitted (e.g., Cancer, major cause of death; Drug and alcohol abuse also affect health). Common Diseases in Humans Pathogens: Disease-causing organisms (bacteria, viruses, fungi, protozoans, helminths), causing harm by living in/on the host and interfering with normal vital activities. Typhoid: Causative Agent: Salmonella typhi (pathogenic bacterium). Transmission: Contaminated food and water, migration to other organs via blood. Symptoms: Sustained high fever (39-40°C), weakness, stomach pain, constipation, headache, loss of appetite. Severe cases can lead to intestinal perforation and death. Confirmation: Widal test. Historical Note: Mary Mallon ("Typhoid Mary") was a carrier. Pneumonia: Causative Agents: Streptococcus pneumoniae and Haemophilus influenzae . Infection Site: Alveoli (air-filled sacs) of the lungs, filling them with fluid. Symptoms: Fever, chills, cough, headache. Severe cases: lips and finger nails may turn gray-bluish. Transmission: Inhaling droplets/aerosols from an infected person, sharing contaminated objects. Common Cold: Causative Agent: Rhinoviruses. Infection Site: Nose and respiratory passage (not lungs). Symptoms: Nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness (lasts 3-7 days). Transmission: Droplets from cough/sneeze (direct inhalation or contaminated objects). Malaria: Causative Agent: Plasmodium (protozoan). Species: P. vivax, P. malaria, P. falciparum (most serious, can be fatal). Life Cycle (Requires Two Hosts: Human & Mosquito): Infectious sporozoites enter human via infected female Anopheles mosquito bite. Multiply in liver cells, then attack RBCs. Rupture of RBCs releases toxic haemozoin, causing chills and high fever (recurring every 3-4 days). Gametocytes taken up by female Anopheles during blood meal. Parasites develop in mosquito, forming sporozoites in salivary glands. Vector: Female Anopheles mosquito. Amoebiasis (Amoebic Dysentery): Causative Agent: Entamoeba histolytica (protozoan parasite). Infection Site: Large intestine. Symptoms: Constipation, abdominal pain, cramps, stools with excess mucus and blood clots. Transmission: Houseflies act as mechanical carriers, transmitting from infected faeces to food/water. Ascariasis: Causative Agent: Ascaris (roundworm, helminth). Symptoms: Internal bleeding, muscular pain, fever, anemia, blockage of intestinal passage. Transmission: Eggs excreted in faeces contaminate soil/water/plants; healthy person acquires via contaminated water/food. Elephantiasis (Filariasis): Causative Agents: Wuchereria bancrofti and W. malayi (filarial worms). Symptoms: Slowly developing chronic inflammation, usually in lymphatic vessels of lower limbs; genital organs often affected, causing gross deformities. Transmission: Female mosquito vectors. Ringworms: Causative Agents: Fungi ( Microsporum, Trichophyton, Epidermophyton ). Symptoms: Dry, scaly lesions on skin, nails, scalp; intense itching. Favorable Conditions: Heat and moisture (skin folds, groin, between toes). Transmission: From soil, or using towels/clothes/combs of infected individuals. Prevention and Control of Infectious Diseases Personal Hygiene: Keep body clean, consume clean food/water. Public Hygiene: Proper waste/excreta disposal, periodic cleaning/disinfection of water reservoirs, control of vectors. For Air-borne Diseases (e.g., Pneumonia, Common Cold): Avoid contact with infected persons and their belongings. For Vector-borne Diseases (e.g., Malaria, Filariasis, Dengue, Chikungunya): Control/eliminate vectors and breeding places. Avoid water stagnation, regular cleaning of coolers. Use mosquito nets. Introduce fish like Gambusia in ponds (feed on mosquito larvae). Spray insecticides. Wire mesh on doors/windows to prevent mosquito entry. Advancements: Vaccines (smallpox eradicated), antibiotics, and other drugs have significantly reduced infectious diseases. Immunity The body's ability to defend itself against disease-causing organisms. Innate Immunity: Non-specific defense, present at birth. Provides various barriers to foreign agents: Physical Barriers: Skin, mucus coating (respiratory, GI, urogenital tracts). Physiological Barriers: Acid in stomach, saliva in mouth, tears from eyes. Cellular Barriers: Leukocytes (PMNLs), monocytes, natural killer cells, macrophages (phagocytose and destroy microbes). Cytokine Barriers: Interferons (proteins secreted by virus-infected cells, protect non-infected cells). Acquired Immunity: Pathogen-specific, characterized by memory. Primary Response: Low intensity on first encounter with pathogen. Secondary (Anamnestic) Response: Highly intensified on subsequent encounters due to memory. Mediated by B-lymphocytes and T-lymphocytes . B-lymphocytes: Produce antibodies (proteins) to fight pathogens. T-lymphocytes: Do not secrete antibodies but help B cells; mediate cell-mediated immunity (CMI). Antibody Structure: Four peptide chains (two light, two heavy), represented as $H_2L_2$. Types of Antibodies: IgA, IgM, IgE, IgG. Humoral Immune Response: Antibody-mediated, as antibodies are found in the blood. Cell-mediated Immunity (CMI): Mediated by T-lymphocytes; responsible for graft rejection (differentiating 'self' from 'non-self'). Active and Passive Immunity Active Immunity: Host produces antibodies in response to antigens (living/dead microbes, proteins). Slow and takes time for full effective response. Induced by immunisation (deliberate injection of microbes) or natural infection. Passive Immunity: Ready-made antibodies are directly given to protect the body. Examples: Colostrum (rich in IgA) from mother to infant, antibodies passed from mother to fetus via placenta. Vaccination and Immunisation Based on the 'memory' property of the immune system. Vaccination: Introduction of antigenic proteins or inactivated/weakened pathogens (vaccine) into the body. Body produces antibodies and memory B and T-cells. Upon actual infection, memory cells quickly recognize and overwhelm invaders. Passive Immunisation: Direct injection of preformed antibodies or antitoxin (e.g., for tetanus, snakebites) when quick immune response is needed. Recombinant DNA Technology: Enables large-scale production of vaccines (e.g., Hepatitis B vaccine from yeast). Allergies Definition: Exaggerated response of the immune system to certain environmental antigens. Allergens: Substances causing allergies (e.g., mites in dust, pollens, animal dander). Antibodies: IgE type antibodies are produced. Symptoms: Sneezing, watery eyes, runny nose, difficulty breathing. Mechanism: Release of histamine and serotonin from mast cells. Diagnosis: Exposure/injection of small doses of possible allergens to observe reactions. Treatment: Anti-histamine, adrenalin, steroids to reduce symptoms. Modern Lifestyle Impact: Lowered immunity and increased sensitivity to allergens, leading to more allergies/asthma in children. Auto Immunity Higher vertebrates can differentiate 'foreign' from 'self' cells. Sometimes, due to genetic or unknown reasons, the body attacks its own self-cells. Auto-immune disease: Damage to the body resulting from the immune system attacking self-cells (e.g., Rheumatoid arthritis). Immune System in the Body Consists of lymphoid organs, tissues, cells, and soluble molecules (antibodies). Recognizes foreign antigens, responds to them, and remembers them. Plays a role in allergic reactions, auto-immune diseases, and organ transplantation. Lymphoid Organs: Sites for origin, maturation, and proliferation of lymphocytes. Primary Lymphoid Organs: Bone Marrow: Main organ where all blood cells (including lymphocytes) are produced. Thymus: Lobed organ near heart, beneath breastbone; large at birth, reduces with age; provides micro-environment for T-lymphocyte maturation. Secondary Lymphoid Organs: Sites for lymphocyte interaction with antigens and proliferation. Spleen, lymph nodes, tonsils, Peyer's patches (small intestine), appendix. Spleen: Large bean-shaped organ, contains lymphocytes and phagocytes; filters blood, traps blood-borne microbes, reservoir of erythrocytes. Lymph Nodes: Small solid structures along lymphatic system; trap microbes/antigens, activate lymphocytes. Mucosa-Associated Lymphoid Tissue (MALT): Lymphoid tissue within major tracts (respiratory, digestive, urogenital); constitutes ~50% of lymphoid tissue. AIDS (Acquired Immuno Deficiency Syndrome) Definition: Deficiency of immune system, acquired during lifetime (not congenital). Causative Agent: Human Immunodeficiency Virus (HIV), a retrovirus with RNA genome. Transmission: Sexual contact with infected person. Transfusion of contaminated blood/blood products. Sharing infected needles (e.g., intravenous drug abusers). From infected mother to child via placenta. High-Risk Individuals: Multiple sexual partners, IV drug abusers, recipients of repeated blood transfusions, children of HIV-infected mothers. Important Note: Not spread by mere touch or physical contact; only through body fluids. Infected individuals should not be isolated. Time-lag: Several months to 5-10 years between infection and AIDS symptoms. Mechanism of Action: HIV enters macrophages, RNA genome replicates to viral DNA via reverse transcriptase. Viral DNA incorporates into host cell DNA, directs production of virus particles (macrophages act as "HIV factory"). HIV enters helper T-lymphocytes ($T_H$), replicates, produces progeny viruses. Progeny viruses released, attack other $T_H$ cells, leading to progressive decrease in $T_H$ cell count. Decreased $T_H$ cells lead to immunodeficiency, making the person susceptible to infections (e.g., Mycobacterium , viruses, fungi, Toxoplasma ) that would otherwise be overcome. Symptoms: Bouts of fever, diarrhea, weight loss, and susceptibility to various infections. Diagnosis: Enzyme-Linked Immuno-Sorbent Assay (ELISA). Treatment: Anti-retroviral drugs (partially effective, prolong life but cannot prevent death). Prevention: Since there is no cure, prevention is key. Education about HIV, safe blood banks, sterile needles/syringes. Free condom distribution, drug abuse control, safe sex advocacy, regular check-ups. Support and sympathy for infected persons, not shunning. Cancer One of the most dreaded diseases, a major cause of death globally. Normal cells have controlled growth and differentiation, showing contact inhibition (inhibition of uncontrolled growth by contact with other cells). Cancer Cells: Lose contact inhibition, divide uncontrollably, forming masses called tumors . Types of Tumors: Benign Tumors: Remain confined to original location, do not spread, cause little damage. Malignant Tumors: Mass of proliferating cells (neoplastic/tumor cells), grow rapidly, invade and damage surrounding normal tissues. Metastasis: Most feared property of malignant tumors; cancer cells slough off, travel via blood to distant sites, and form new tumors. Causes of Cancer (Carcinogens): Agents inducing transformation of normal cells into cancerous cells. Physical Agents: Ionizing Radiations: X-rays, gamma rays (cause DNA damage). Non-ionizing Radiations: UV light (cause DNA damage). Chemical Agents: Tobacco smoke constituents (major cause of lung cancer). Biological Agents: Oncogenic Viruses: Viruses with genes called viral oncogenes . Cellular Oncogenes (c-onc) / Proto-oncogenes: Genes in normal cells that, when activated under certain conditions, can lead to oncogenic transformation. Detection and Diagnosis: Early detection is crucial for successful treatment. Biopsy & Histopathological Studies: Tissue examination by pathologist. Blood & Bone Marrow Tests: For leukemias (increased cell counts). Radiography (X-rays), CT (Computed Tomography): For internal organ cancers; CT provides 3D images. MRI (Magnetic Resonance Imaging): Uses strong magnetic fields and non-ionizing radiations for accurate detection of pathological/physiological changes. Antibodies: Against cancer-specific antigens. Molecular Biology: Detects genes with inherited susceptibility to cancers, aiding prevention. Treatment of Cancer: Surgery: Removal of tumor. Radiation Therapy: Irradiating tumor cells lethally while protecting normal tissues. Chemotherapy: Drugs to kill cancerous cells (some tumor-specific, side effects include hair loss, anemia). Immunotherapy: Use of biological response modifiers (e.g., $\alpha$-interferon) to activate the immune system and destroy tumors. Most cancers treated with a combination of these methods. Drugs and Alcohol Abuse Rising concern, especially among youth, leading to harmful effects. Commonly Abused Drugs: Opioids, Cannabinoids, Coca alkaloids. Opioids: Bind to specific opioid receptors in CNS and gastrointestinal tract. Heroin (Smack): Chemically diacetylmorphine; white, odorless, bitter, crystalline. Source: Acetylation of morphine, extracted from latex of opium poppy ( Papaver somniferum ). Administration: Snorting, injection. Effects: Depressant, slows down body functions. Cannabinoids: Interact with cannabinoid receptors in the brain. Source: Inflorescences of Cannabis sativa (flower tops, leaves, resin). Forms: Marijuana, hashish, charas, ganja. Administration: Inhalation, oral ingestion. Effects: Affect cardiovascular system. Coca Alkaloid (Cocaine/Coke/Crack): Source: Erythroxylum coca (coca plant), native to South America. Mechanism: Interferes with dopamine neurotransmitter transport. Administration: Usually snorted. Effects: Potent CNS stimulant, euphoria, increased energy. Excessive Dosage: Causes hallucinations. Other Hallucinogenic Plants: Atropa belladona, Datura . Other Abused Drugs (Medicines): Barbiturates, amphetamines, benzodiazepines (sedatives, painkillers, used for depression/insomnia, often abused). Anabolic Steroids: Misused by sportspersons to enhance performance. Side Effects in Females: Masculinization, increased aggressiveness, mood swings, depression, abnormal menstrual cycles, excessive hair growth, clitoris enlargement, voice deepening. Side Effects in Males: Acne, increased aggressiveness, mood swings, depression, reduced testicular size, decreased sperm production, kidney/liver dysfunction, breast enlargement, premature baldness, prostate gland enlargement. Common Effects (Adolescents): Severe facial/body acne, premature closure of growth centers (stunted growth). Adolescence and Drug/Alcohol Abuse Adolescence: Period (12-18 years) of physical, mental, and psychological development. Causes of Abuse: Curiosity, need for adventure/excitement, experimentation. Escape from problems, stress (academic/examination pressures). Perception of being 'cool' or progressive (influenced by media). Unstable/unsupportive family structures, peer pressure. Tobacco Use: Contains nicotine (stimulates adrenal gland to release adrenaline/nor-adrenaline, increasing blood pressure/heart rate). Associated with cancers (lung, urinary bladder, throat), bronchitis, emphysema, coronary heart disease, gastric ulcer. Chewing tobacco associated with oral cavity cancer. Increases CO in blood, reduces oxygen-carrying capacity. Highly addictive; requires counseling/medical help to quit. Addiction and Dependence Addiction: Psychological attachment to effects (euphoria, well-being) of drugs/alcohol. Drives repeated use even when harmful. Tolerance Level: Increases with repeated use, requiring higher doses, leading to greater intake and addiction. Dependence: Body manifests characteristic withdrawal syndrome if regular use is abruptly stopped. Symptoms: Anxiety, shakiness, nausea, sweating (relieved by resuming use). Can be severe, life-threatening, requiring medical supervision. Leads to ignoring social norms, seeking funds, social adjustment problems. Effects of Drug/Alcohol Abuse Immediate Adverse Effects: Reckless behavior, vandalism, violence. Severe Effects: Excessive doses can lead to coma, death (respiratory failure, heart failure, cerebral hemorrhage). Warning Signs in Youth: Drop in academic performance, unexplained absence, lack of hygiene, withdrawal, isolation, depression, fatigue, aggressive/rebellious behavior, deteriorating relationships, loss of interest in hobbies, changes in sleep/eating habits, weight fluctuations. Social Impacts: Stealing for money to buy drugs/alcohol, mental/financial distress to family/friends. Long-term Effects (Alcohol): Heavy drinking in adulthood, damage to nervous system and liver (cirrhosis). During Pregnancy: Adversely affects the fetus. Prevention and Control of Drug/Alcohol Abuse Prevention is Better Than Cure: Early identification of situations pushing adolescents towards abuse. Role of Parents and Teachers: Nurturing, consistent discipline. Measures: Avoid Undue Peer Pressure: Respect individuality, avoid pushing beyond limits. Education and Counseling: Help face problems, accept disappointments, channel energy into healthy pursuits (sports, reading, music, yoga). Seeking Help: From parents, peers, trusted friends to vent feelings; from professionals (psychologists, psychiatrists) and de-addiction/rehabilitation programs. Looking for Danger Signs: Alert parents/teachers/friends to identify signs of abuse and seek appropriate remedial steps.