Please give me a short summary/ notes of the chapter ' why do we fall ill' .

Why Do We Fall Ill **Health and Disease * Health - A state of physical, mental, and social well-being that includes a unity and harmony within the mind, body, and soul of an organism * Disease - Any condition that can lead to discomfort, distress, health problems, and even death of the affected person * Symptoms - Indications of disease, such as headache, stomach pain, nausea, etc that can only be felt by the patient * Signs of a disease include fever, vomiting, diarrhoea, etc that can be observed by a physician * Incubation period - The time interval between infection and appearance of symptoms **Causes of diseases * On the basis of its duration - Acute and Chronic * Acute - Lasts for a short period of time, eg. Cold, cough, influenza, etc. * Chronic - Lasts for long periods of time, eg. Diabetes, kidney stones, etc. * On the basis of causative agents - Infectious and Non-infectious * Infectious - Diseases such as influenza, cold, etc., which are caused due to infectious agents * Non-infectious - Diseases such as high blood pressure, cancer, etc., which are caused by some internal causes such as excessive weight, genetic defects, etc. ***Infectious agents **They are the disease-causing microorganisms which belong to different categories such as: * Viruses - These are tiny organisms that grow, multiply, or reproduce only inside the host cells * Diseases caused by viruses - Influenza, cold (Rhinovirus), dengue, AIDS, SARS etc. * Bacteria - These are unicellular organisms; larger than viruses * Diseases caused by bacteria - Whooping cough, typhoid, cholera, anthrax, etc. * Fungi - These are plant-like organisms; heterotrophic * Diseases caused by Fungi - Athlete’s foot, candidiasis, ringworms, etc. Protozoa - **These are simple, primitive unicellular organisms which are often found in water * Diseases caused by Protozoa - Amoebiasis, kala azar, malaria, African sleeping sickness, etc. Sleeping sickness is caused by Trypanosoma and Kala azar is caused by Leishmania * Multicellular animals like worms - These are parasites that infect the intestines of human beings and other animals * Diseases caused by worms- Diarrhoea, liver rot, etc. Communicable diseases * An infectious disease is classified as communicable disease when it can be transferred from an infected person to a healthy person ***Means of disease spread **They are the disease-causing microorganisms which belong to different categories such as: * Air-borne diseases - Transmitted when disease-causing microorganisms are expelled into the air by coughing, sneezing, talking, etc. E.g. common cold, chicken pox, small pox, pneumonia, influenza, tuberculosis, etc. * Water-borne diseases - Spreads when the excretions (from an infected person) containing causal microorganisms get mixed with drinking water and this contaminated water is consumed. E.g. cholera, typhoid, hepatitis A, etc. * Physical contact – Includes sexually-transmitted diseases. E.g. syphilis, gonorrhoea, AIDS, etc. * Blood to blood contact – Such contact is established during blood transfusion or pregnancy (between the mother and her baby). E.g. AIDS can spread through blood contact * Animals – Animals that transfer disease-causing microorganisms from an infected person to others are called vectors. E.g. female mosquitoes can transfer the malariacausing Plasmodium **Effects of diseases * Local effects - Includes swelling, pain, joint stiffness, etc., that occur only at the site of infection * General effects - Includes fever chills, headaches, fatigue, loss of appetite, etc., that occur all over the body Inflammation- The process by which the body’s immune system shows response to protect the body from infection **Prevention of diseases * Antigens - Foreign substances that invade our body * Immunisation - The protection of the body from communicable diseases by administration of some agent that mimics the microbe. * Vaccine: The suspension of killed microbes that mimics the disease causing microbes. * Vaccines available against tetanus, polio, measles, hepatitis B, etc Source -> Revision notes from merit nation of science of chapter 13. Why do we fall ill ? Hope this helps !! :)