Revision: Health and Diseases General Science SSC (English Medium) 8th Standard Maharashtra State Board

It is to maintain a stable equilibrium of the body in accordance with the pressures and changes of the body environment.

A pathogen is a biological agent that causes disease to its host. e.g. bacteria, virus, etc.

Any deviation from normal state of health is called disease.

Disease:
The disease can be defined as an impairment or malfunctioning of the normal state of the living organism that disturbs or modifies the performance of vital functions of the body.

A disease caused by a specific pathogenic organism and capable of being transmitted to another individual by direct or indirect contact is known as communicable (infectious) disease.

Adverse functioning of one or more organs or systems of the body, characterised by specific signs and symptoms, is called disease.

A disease not caused by pathogenic organisms and not transmitted from one person to another by direct or indirect contact is known as a non-communicable (non-infectious) disease.

or

The diseases which don’t spread from infected person to a healthy person are known as non-communicable or non-infectious diseases.

Malignant tumour is a cancerous tumour that grows rapidly, invades surrounding tissues and spreads to distant organs.

Cancer is a disease characterised by uncontrolled and abnormal division of body cells due to loss of normal growth regulation.

Metastasis is the process by which cancer cells spread from the primary site to distant organs through blood or lymph.

Tumour is a mass of abnormally proliferating cells formed due to uncontrolled cell division.

Benign tumour is a non-cancerous tumour that remains confined to its original site and does not spread to other parts of the body.

The process of administering a vaccine to stimulate the immune system and provide protection against infectious diseases is called vaccination.

A preparation containing specific antigens that is administered to induce temporary or permanent immunity against a particular disease is called a vaccine.

Preparation of antigenic proteins of pathogens (weakened or killed) which on inoculation into a healthy person provides temporary/permanent immunity against a particular disease.

Antibiotics are metabolic products of microorganisms whose very low concentrations are inhibitory or detrimental to other microbes.

Infection is the entry, development, or multiplication of an infectious agent in the human body or animals.

• Communicable / Infectious diseases are caused by pathogens and spread from an infected to a healthy person via air, water, food, vectors, or contact.
• Common pathogens: bacteria (cholera, typhoid, TB), viruses (AIDS, hepatitis), protozoa (malaria), and helminths (ascariasis, filariasis).
• Incubation period: time between infection and symptoms — varies from hours (cholera) to years (HIV/AIDS, leprosy).
• TB (Mycobacterium tuberculosis) spreads through air; prevented by BCG vaccine, isolation, and DOTS.
• Hepatitis spreads through contaminated water, needles, or blood; prevented by boiled water and hygiene.
• Cholera, typhoid, and dysentery spread through contaminated food and water; prevented by hygiene, boiled water, ORS, and vaccination.

• Common cold is caused by Rhinovirus, spreads via droplets from cough/sneezes and contaminated objects, with symptoms like nasal congestion, sore throat, and headache, lasting 3-7 days.
• Dengue and Chikungunya are both spread by the Aedes mosquito; Dengue is caused by the Dengue virus and Chikungunya by the CHIK virus.
• Influenza spreads via coughing/sneezing, Measles spreads via droplets, while Mumps and Chickenpox spread through airborne droplets.
• German measles spreads via close contact, Smallpox via direct contact, and Rabies is transmitted through the bite of a rabid dog.
• Polio is caused by the polio virus and spreads via faeces and air, seriously affecting the nervous system.
• Avian flu is caused by the H5N1 virus and spreads through contact with infected poultry as well as through airborne spread.
• Chickenpox is caused by Varicella zoster and spreads via airborne droplets, while Smallpox, caused by Variola virus, spreads via direct contact and is now globally eradicated.

• Vaccination and immunisation work on the immune system's memory.
• A vaccine may contain a weakened pathogen, an inactivated pathogen, or antigenic proteins.
• The body produces antibodies against these antigens.
• Memory B-cells and T-cells enable a faster response during later exposure.
• Passive immunisation involves direct injection of preformed antibodies or antitoxins.
• Examples of passive immunisation include tetanus and snakebite treatment.
• Vaccines may be made from protein or sugar from a pathogen, a dead or inactivated pathogen, a toxoid, or a weakened pathogen.
• Antigenic polypeptides can also be produced using recombinant DNA technology in bacteria or yeast.