| S.No. | Active Immunity | 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 all the peripheral blood vessels and the capillaries become highly permeable so that large amounts of fluid leak out from the blood into the tissues.
(1) Hay fever : In this allergic form, there is swollen, reddened, running eyes and nose. The drugs called antihistamines are of major importance in the treatment of this allergic disorder.
(2) Asthma : The tissue surrounding the respiratory tubes in the lungs swell up and compress the tubes. Hence there is difficulty in breathing. Antihistamine drugs are also given in this disease.
(3) Anaphylactic shock : It is an allergic reaction involving all the tissues of the body and occurs in a few minutes after the injection of an antigen such as penicillin. Such a reaction is very serious. Histamine released from ruptured mast cells causes marked dilation of all the arteries so that a large amount of fluid is passed from the blood to the tissues and there is a drastic fall in blood pressure. The affected person may become unconscious and the individual may die within a short time.
Autoimmunity : Sometimes it may also happen that the immune system of the body goes off the track and starts behaving against the ‘own body’ or ‘self’. This leads to a variety of diseases known as autoimmune diseases. This type of diseases depends on which type of ‘self-antigen’ is involved. When the cells acting as antigens in the same body, they are called autoantigens. The nature of autoimmune diseases depends on the autoantigens involved. For example, if the autoantigens are RBC then the body destroys its own RBC, resulting in chronic anaemia; if the autoantigens are muscle cells then it results in the destruction of its own muscles resulting in severe weakness (myasthenia gravis); if the autoantigens are liver cells, then it results in chronic hepatitis, etc. Other autoimmune diseases are insulin-dependent diabetes, Addison’s disease, ulcerative colitis and rheumatoid arthritis.
Immuno deficiencies
(1) Severe Combined Immuno deficiency (SCID) : Sometimes new born children are without T-cells and B-cells. These children are highly susceptible to various infections. The most serious disorder of this type 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 friction or other mechanical forces which result in injury, sprain, dislocation fracture.
(6) Deficiency and Excess of substances : e.g. Hormones, enzymes.
Some diseases are caused by genetic disorders and lack or underdevelopment of organs. The agents for certain diseases such as peptic ulcers, coronary heart diseases and hypertension, are not fully known.
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 :
(1) Non-specific Defence Mechanism : It is further of two types : external defence or first line of defence and internal defence or second line of defence.
(i) External Defence : It includes physical and chemical barriers.
(a) Physical Barriers
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 well developed colony of bees had 40 to 50 thousand individuals consisting of 3 castes viz. queen, drone and worker.
(1) The Queen : It is a well developed fertile female provided with immensely developed ovaries. Commonly one queen is found to be present in each hive and feeds on Royal Jelly. The queen is 15 to 20 mm in length and can be easily distinguished by her long tapering abdomen, short legs and wings. Structurally she is unable to produce wax or honey or gather pollen nector. By the combination of ovipositor-cum sting, a structure is developed which aids in egg laying. It is said that the queen gets mated only in her life but in a single chance of mating, drone releases two crore sperms which are sufficient for the fertilization of the eggs at the time of laying by the female throughout her life span.
One queen lays about \[1,5002,000\] eggs in day. In the whole life span of 2-5 years a queen lays about 15,00,000 eggs. When the queen in a colony looses its eggs lying capacity, another worker of the same colony starts feeding on queen’s diet i.e., Royal Jelly and develops into a new queen and is provided with the facilities of real queen. At the same time old queen may be driven out but sometimes some workers object that as to why the mother of the colony be driven out so ultimately they also come out with the mother. Sometimes when 2 to 3 queens are developed in a colony, only one takes the position of the real queen and the others come out with some workers to establish new colonies. This phenomenon is known as swarming.
(2) The Drone : The drone is the male member of the honey bee colony which fertilizes the queen so called as king of the colony. They are reared from an unfertile egg in large drone cell. Drone are totally dependent on the workers and have been seen begging for honey from the workers. The sole duty of the drone is to fertilize the virgin queen. 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 size of the hump is a good indicator of its health.
Breeding : There are four kinds of camels in India. These are Jaisalmeri, Sindhi and Bikaneri found in Rajasthan and Kutchi found in Gujrat. They have a well-defined breeding season. Camels breed in winter (November to March).
Diseases : Camels suffer diseases such as anthrax, pneumonia, camel-pox and surra.
12th ClassCurrent Affairs CategoriesArchive
Trending Current Affairs
You need to login to perform this action. |
