Revision: Biology and Human Welfare >> Human Health and Diseases Biology Science (English Medium) Class 12 CBSE

The overall ability of the host to fight the disease-causing organisms conferred by the immune system is called immunity.

Health is defined as the state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.

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

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

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

The exaggerated response of the immune system to certain antigens present in the environment is called allergy.

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to something in the environment that usually causes no adverse effects to most people. These diseases include hay fever, dermatitis, asthma, food allergies, etc.

Autoimmune response is an immune reaction in which antibodies or immune cells are produced against the body’s own antigens.

Autoimmune disease is a pathological condition caused due to autoimmunity, where self-tissues are damaged or destroyed by the immune system.

Autoimmunity is the condition in which the immune system fails to recognise self and reacts against the body’s own cells and tissues.

The antibody-mediated defence mechanism is called humoral immune response.

The immunity developed during an individual’s lifetime after exposure to antigens is called acquired (specific) immunity.

The hereditary, non-specific protection present from birth is called innate (natural) immunity.

The system of defence mechanisms that protects the body against harmful agents is called immune system.

The defence mechanism involving lymphocytes and macrophages without antibody production is called cell-mediated (cellular) immune response.

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

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

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

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

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

A cancer-causing gene that induces transformation of normal cells into cancerous cells is called an oncogene.

A normal cellular gene involved in growth and development, which can become an oncogene after mutation or activation, is called a proto-oncogene.

Agents that cause cancer by disturbing the normal genetic and regulatory processes of cells are called carcinogens.

Innate immunity is the inborn, non-specific defence that protects the body from pathogens from birth.

The process by which an individual acquires protection against a specific disease through vaccination or antibody administration is called as immunisation.

The process of providing immediate protection by injecting preformed antibodies into the body is called as passive immunisation.

The exaggerated or hypersensitive immune response of the body to certain harmless environmental substances is called as allergy.

The substance that triggers an allergic immune response in a sensitive individual is called as allergen.

The condition in which the immune system fails to distinguish self from non-self and attacks the body’s own cells is called as autoimmunity.

A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity is called health.

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

Diseases that are easily transmitted from one person to another are called infectious diseases.

Diseases that do not spread from one person to another and arise due to genetic factors, lifestyle or physiological disorders are called non-infectious diseases.

Organisms such as bacteria, viruses, fungi, protozoans and helminths that cause diseases in humans are called pathogens.

The immunity developed when the body produces its own antibodies in response to exposure to antigens through infection or vaccination is called as active immunity.

The immunity obtained by the direct transfer of ready-made antibodies from another individual is called as passive immunity.

The process of introducing weakened or inactivated pathogens or their antigenic components into the body to induce immunity is called as vaccination.

• The immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies that protect the body against foreign antigens.
• It has the unique ability to recognise antigens, respond to them and retain memory for faster and stronger responses on repeated exposure.
• Primary lymphoid organs (bone marrow and thymus) are responsible for the origin, development and maturation of lymphocytes.
• Secondary lymphoid organs such as spleen, lymph nodes, tonsils, Peyer’s patches and appendix are sites where lymphocytes interact with antigens and initiate immune responses.
• Mucosa-associated lymphoid tissue (MALT), present in respiratory, digestive and urogenital tracts, forms nearly 50% of the body’s lymphoid tissue and provides defence at body surfaces.