12th Class

The main non-communicable diseases are diabetes, inflammatory diseases of joints such as arthritis, gout, cardiovascular diseases and cancer. (1) Diabetes Mellitus (i) Diabetes is characterised by chronic hyperglycemia which is excessive concentration of glucose in the blood. (ii) Diabetes is primarily a result of relative or complete lack of insulin secretion by the \[\beta \] cells of islets of Langerhans in pancreas. (iii) Diabetes is established by blood and urine sugar levels. (2) Arthritis (i) Arthritis is any inflammatory condition of the joints characterised by pain and swelling. (ii) Two kinds of arthritis are : rheumatoid arthritis and osteoarthritis. (iii) There is no cure for arthritis; drugs are available which relieve pain. (iv) Rheumatoid arthritis is characterised by inflammation of the synovial membrane. (v) A kind of rheumatoid arthritis that occurs in younger people is Still’s disease. (vi) Osteoarthritis is a disease common among the elderly persons resulting from erosion more...

Meaning : The diseases which are caused by pathogens (viruses and living organisms) and readily spread from the infected to the healthy persons are called communicable or infectious diseases. A German physician, Robert Koch, listed the following four conditions to establish that a specific pathogen causes a particular disease - (1) The suspected pathogen should be invariably present in the animals suffering from the disease and should not be found in healthy individuals. (2) The pathogens isolated from the diseased animal should be grown in a pure culture. (3) When this culture is inoculated into a healthy host, the latter should develop the disease and show its characteristic symptoms. (4) The pathogen should be recoverable from the experimental host, and it should be the same as the original one. Kotch’s postulates proposed for animal diseases, hold good for human diseases also. However, his conditions do not apply to viruses because more...

History of Vaccines and Vaccination : In vaccination weakened or dead pathogens, or portions of pathogens, are injected into a person who is required to be made immune. The pathogens given in a vaccine are unable to cause the disease, but are sufficient to stimulate the formation of antibodies by host’s cells. The process of vaccination was initiated by Edward Jenner in 1790. He observed that milkmaids did not contract smallpox apparently because they were exposed to a similar but milder form of disease called cowpox. Edward Jenner infected first James Phipps,, a healthy boy of about 8 years with cowpox and two months later he infected the boy with smallpox. The boy did not suffer from small pox. Jenner proposed that an induced mild form of a disease would protect a person from a virulent form (which has ability to damage the host). He used the term vaccine (in more...

The diseases may be broadly classified into two types : Congenital and acquired. (1) Congenital Diseases : These are anatomical or physiological abnormalities present from birth. They may be caused by (a) a single gene mutation (alkaptonuria, phenylketonuria, albinism, sickle-cell anaemia, haemophilia, colour blindness); (b) chromosomal aberrations (Down’s syndrome, Klinefelter’s syndrome, Turner’s syndrome); or (c) environmental factors (cleft palate, harelip). Unlike the gene-and chromosome-induced congenital defects, environmentally caused abnormalities are not transmitted to the children. (2) Acquired Diseases : These diseases develop after birth. They are further of two types : communicable and non-communicable. (i) Communicable (Infectious) Diseases : These diseases are caused by viruses, rickettsias, bacteria, fungi, protozoans and worms. (ii) Noncommunicable (Noninfectious) Diseases : These diseases remain confined to the person who develops them and do not spread to others. The non-communicable diseases are of four kinds : (a) Organic or Degenerative Diseases : These diseases are due more...

Definition : The resistance of the body to occurrence of any disease is known as immunity. Study of the ability of an organism to resist a disease is called immunology. Development of Immunity : A person may develop immunity in three ways. (1) Vaccination : It is a technique to develop immunity without infection. Weakened or dead pathogens (attenuated) or parts of pathogens are injected into a person who is required to be made immune. The pathogens given in a vaccine are unable to cause the disease but are sufficient to stimulate the formation of antibodies by the host’s immune system. Often 2 or 3 additional doses are needed to generate adequate immunity. These doses are called booster doses. (2) Antitoxins : Antibodies that neutralize toxins produced in the body or introduced from outside are, called antitoxins. Bacterial toxins are produced in the body, however antitoxins produced from outside are more...

Allergies : Allergy is the hypersensitiveness of a person to some foreign substance coming in contact with or entering the body. The substances that cause allergic reaction are called allergens. The common allergens are dust, pollen mould, spores, fabrics, lipsticks, nail paints, feathers, fur, plants, bacteria, foods, heat, cold, sunlight. Symptoms : The symptoms that result from an allergy may be of different kinds but mostly it affects the skin and mucous membrane. Hay fever affects the mucous membranes of the nose, eyes and upper respiratory tracts. In asthma, the lower portions of the respiratory system are severely affected. In eczema the skin becomes red, followed by the appearance of minute blisters. Eczema may affect any part of the body and is one of the most severest of all allergic symptoms. Cause : During allergic reaction there is increased release of histamine from mast cells. It causes marked dilation of more...

The disease agent is a factor (substance or force) which causes a disease by its excess or deficiency or absence. These agents are of five main types : (1) Biological Agents : These include viruses, rickettsias, bacteria, fungi, protozoans, helminthes and arthropods. The biological agents are called pathogens (Gr. Pathos = disease; genes = producing). (2) Nutrient Agents : These comprise food components such as carbohydrates, fats, proteins, minerals, vitamins and water. (3) Chemical Agents : These are further of two types (i) Endogenous Chemical Agents : These are formed in the body itself and include hormones, enzymes, urea and uric acid. (ii) Exogenous Chemical Agents : These enter the body from outside by inhalation, ingestion or inoculation. Pollutants (fumes, gases, dusts, metals) and allergens (spores, pollen) are examples. (4) Physical Agents : These include heat, cold, humidity, pressure radiation, electricity and sound. (5) Mechanical Agents : These comprise chronic more...

Immune response : Nature has provided certain ways in the body to defend ourselves from the invention of pathogens and therefore, from the disease. The ability of a host’s body to prevent or overcome the effects caused due to the invention by pathogenic organisms and its toxins is known as resistance and immunity. Resistance is considered as an inherent factor and those acquired during life to overcome the disease, while the immunity is accepted to be due to the acquired factors that help in resistance. The host body has two lines of defence that must be overcome by a pathogen before establishing an infection. External defence mechanism : This defence mechanism involves mechanical and chemical factors e.g. skin, mucous membrane, mucous secretion, peristalsis, coughing, sneezing, shedding tears, etc. Chemicals are lysozymes present in the body. Internal defence mechanism : This mechanism of defence has two lines of defence against pathogen more...

Apiculture is the science of rearing honeybees for obtaining honey, wax and venom. It is a profitable money-making hobby. It forms a cottage industry, when carried out on a large scale. Three species of honey bees are commonly found in india vig. Apis indica (The small indian bee), Apis florea (The little indian bee) and Apis dorsata (the giant bee) other important species include Apis mellifera (the common European bee) and apis adamsoni (the African bee) In india the commonly domesticated species are Apis milifera and Apis Indica. Honeybee-Apis : Like termites, honeybees are social insects known for producing honey and beeswax, and for living in very highly organized colonies. These feed upon nectar and pollen of flowers, possess “sucking and chewing” mouth parts, and undergo complete metamorphosis. Social Organisation of Honey Bee A highly organised division of labour is found in the colony of honey bees. A good and more...

The camel is a large, horn less, ruminant mammal of genus Camelus. It is popularly called “the ship of the desert” because of its great travelling power in a desert. It is a valuable beast of burden in hot desert and semidesert regions as it can live on minimum food and water when travelling with load. Types of camels : There are two types of camels : (1) Arabian camels (Camelus dromidarius) : With a single hump, short hair and found in north Africa to India. It does not occur in wild form. (2) Turkish or bactrian camel (Camelus bactrianus) : With two humps, long hair and found in Gobi desert of central Asia. It occurs in wild form also. Feeding : Camels are fed on dry fodder (barley, straw) supplemented with chopped green fodder made of pulses, mustard and green pees. They browse on trees, shrubs and bushes. The more...