Human Health and Disease

Flashcards covering vocabulary, types of diseases, the immune system, diagnostic tests, and drug/alcohol abuse from the Class XII Biology lecture notes.

Health

A state of complete physical, mental and social well-being rather than only the absence of disease or physical illness.

Good Humor Hypothesis

An early belief asserted by Greeks like Hippocrates and the Indian Ayurveda system that health was a state where there was a balance of certain 'humors'.

William Harvey

The scientist who disproved the 'good humor' hypothesis by discovering blood circulation and demonstrating normal body temperature in people with black bile using a thermometer.

Disease

A condition characterized by various signs and symptoms where the functioning of one or more organs or systems is adversely affected.

Pathogens

Disease-causing organisms such as bacteria, viruses, fungi, protozoans, and helminthes that multiply and cause harm by interfering with vital activities.

Typhoid

A bacterial disease caused by $Salmonella typhi$ which enters the small intestine via contaminated food and water; confirmed by the Widal test.

Pneumonia

An infection of the lung alveoli caused by $Streptococcus pneumoniae$ and $Haemophilus influenzae$, often resulting in lips turning gray to bluish in severe cases.

Common Cold

A viral infection caused by Rhino viruses that affects the nose and respiratory passages but not the lungs.

Amoebiasis

A protozoan disease caused by $Entamoeba histolytica$ transmitted through contaminated food and water via houseflies as vectors.

Filariasis (Elephantiasis)

A chronic inflammation and deformation of organs caused by $Wuchereria bancrofti$ and transmitted by the female culex mosquito.

Hemozoin

A toxic substance released from ruptured red blood cells ($RBCs$) during the infection of $Plasmodium$, responsible for the chill and high fever in malaria.

Immunity

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

Innate Immunity

A type of non-specific immunity present at the time of birth, providing physical, physiological, cellular, and cytokine barriers.

Lysozyme

An antibacterial agent found in saliva and tears that acts as a physiological barrier in innate immunity.

Diapedesis

The amoeboid movement by which polymorpho-nuclear leukocytes ($PMNL$-neutrophils) exit blood capillaries to phagocytose and destroy microbes.

Interferons

Proteins secreted by virus-infected cells that protect non-infected cells from further viral infection as part of the cytokine barrier.

Acquired Immunity

Pathogen-specific immunity characterized by memory, including primary responses to first encounters and intensified secondary (anamnestic) responses.

Antibodies

Army of proteins produced by B-lymphocytes in response to pathogens; structurally represented as $H_2L_2$ (two heavy and two light chains).

IgA

A secretory antibody found in saliva, tears, and colostrum (early mother's milk) that provides protection to infants.

Cell Mediated Immune Response (CMI)

Immune response carried out by T-cells which detects and destroys foreign or cancerous cells and is responsible for organ transplant rejection.

Active Immunity

A slow but long-lasting type of acquired immunity where the body produces its own antibodies against antigens during natural infection or immunization.

Allergy

An exaggerated response of the immune system to environmental antigens (allergens) mediated by $IgE$ antibodies and chemicals like histamine.

Auto Immunity

A condition where the body attacks its own self-cells due to genetic or unknown reasons, such as in Rheumatoid arthritis.

Thymus

A primary lymphoid organ large at birth but reducing in size with age; often called the juvenile gland where T-lymphocytes mature.

MALT (Mucosa Associated Lymphoid Tissue)

Lymphoid tissue located within the lining of major tracts (respiratory, digestive, urogenital), constituting about $50$ percent of total lymphoid tissue.

AIDS (Acquired Immuno Deficiency Syndrome)

A non-congenital deficiency caused by the Human Immuno Deficiency Virus ($HIV$), first reported in America in $1981$.

Reverse Transcriptase

The enzyme used by the $HIV$ RNA genome to replicate into viral $DNA$ within host macrophages.

Contact Inhibition

A property of normal cells where contact with other cells inhibits uncontrolled growth, a property lost in cancer cells.

Metastasis

The most feared property of malignant tumors where cells slough off to reach distant sites through blood and develop new tumors.

MRI (Magnetic Resonance Imaging)

A diagnostic technique using strong magnetic fields and non-ionising radiations to accurately detect pathological and physiological changes in living tissue.

Heroin

Commonly called 'smack' and chemically known as diacetylmorphine; it is an opioid obtained by acetylation of morphine extracted from $Papaver somniferum$.

Cannabinoids

Chemicals obtained from $Cannabis sativa$ that interact with brain receptors and affect the cardiovascular system.

Cocaine

An alkaloid obtained from $Erythroxylum coca$ that stimulates the central nervous system by interfering with the neurotransmitter dopamine.

Withdrawal Syndrome

The characteristic and unpleasant effect manifested by the body if regular use of addictive drugs or alcohol is discontinued.