The disease causing agents can be classified as follows:

• 1. Genetic or inherited causes: These causes are transmitted to the offspring through the germplasm.
• (a)   Sub factors: Some factors cause death in utero or after birth death.
• (b)   Sub lethal factors: Those factors, which are inherited and interfere with the function of the body but do not cause death.
• (c)   Defects that are inherited errors in structure or function.
• 2. Non-genetic or Non-inherited defects : These causes do not transmitted through the germ plasma. These are caused by anything but not genetic.

Endemic and Epidemic diseases

Endemic is a disease is generally confined to certain area because the conditions are such as would promote that disease, such as Malaria in marshy areas or leprosy in Tehri-Garhwal.Epidemic occurs when disease breaks out and spreads from one place to another colourless stools and also vomiting, pain in legs and back, camps, suppression of urine and collapse.

Viruses

(Latin-Venom or poisonous fluid): The viruses were first discovered by lwanowski (1892) as extremely small microorganisms. The viruses are the simplest forms of life which instead of having cellular organization (viz. plasma membrane, cytoplasm and nucleus) similar to bacteria, blue green algae, plants and animals contain definite genetically determined macromolecular organization, genetic material and characteristic mode of inheritance.

It is very difficult to categories, viruses in any one of two groups of living and non-living. Because the viruses are non-living outside the cell body (host) and can even by stored in bottles for any length of time just like non-living things. They lack a necessary energy yielding and synthetic enzyme system and therefore they can not lead an independent mode of life Viruses replicate and behave like living beings only within the living cells. For this reason they are a link between living and non-living things, and al are strictly parasitic.

Differences between bacteria and viruses

1.    Viruses have only one type of nucleic acid either DNA or RNA. Whereas bacteria have got both.

2.    Viruses are devoid of ribosomes and the enzyme systems needed to generate ATP molecules. Whereas bacteria have got ribosomes as well as enzymes needed in ATP synthesis.

3.    Viruses lack various cytoplasmic organelles. Whereas bacteria have cytoplasmic organelles.

4.    Viruses do not have cell wall but bacteria have well defined cell wall.

5.    Viruses cannot multiply or synthesize their proteins and enzymes independent on the host cell, but, bacteria can.

Different disorders

Developmental disorders  

Arrest of development: Includes Agenesia or aphasia (Complete absence of a body part),          Hypoplasia( Reduction in size of a body part),  Atresia(closure of anal opening) etc .

Excessive development: inlcudes (i)              Congenital hypertrophy: Increase in the size of the organ. Example: Ventricular hypertrophy is the hypertrophy of the myo cardium of the ventricle.(ii)             Increase in number-Example: Polydactyla is the presence of supernumerary digits on the hands or feet.

Inflammation

It is the reaction of the living tissue to injury or is the reactive process to a sub lethal injury to tissue and end with complete healing. It is the protective mechanism to destroy and remove the irritant. It includes

1.    Redness (increased blood supply);

2.    Swelling (due to more blood in that part);

3.    Heat (Increase metabolism);

4.    Pain (due to increase pressure on the nerve endings),

5.    Loss of function.

Necrosis

 The local death of the tissue in a living body is necrosis and the death of the body as a whole is called somatic death. The changes that take place gradually in the cells while they are dying are known as necrobiosis.

Gangrene

Necrosis of tissues with putrification by saprophytic bacteria is called gangrene.

Hyperemia or Congestion

The condition in which there is increased amount of blood in the blood vessels of the body.

Ischemia

Local deficiency of arterial blood in an organ.

Hemorrhage

Escape of blood from an artery, vein or capillary to the outside or into the body cavity or into tissue.

Epistaxis: Bleeding from nose.

Hematemesis: Blood in vomit

Hemoptysis: Blood in sputum

Metrorrhagia: Bleeding from uterus

Enterorrhagia: Bleeding from Alimentary Canal

Melena: Blood in stools.

Hematuria: Blood in urine

Hemothorax: Blood in the thoracic cavity.

Hemorpericard: Blood in the pericardium

Hematocele: Bleeding into tunica aginicis

Hemosalpinx: Bleeding in oviducts.

Hematoma: A tumour like accumulation of blood in the tissue.

Apoplexy: Hemorrhage into the brain

Infectious Diseases

These are conveyed from one person to another by

(a)   Air, e.g. Tuberculosis, influenza, Smallpox.

(b)   Inanimate objects (such as clothes, books, furniture) e.g. Scarlet fever and small pox.

(c)   Water and food, e.g. Cholera, Dysentery

(d)   Through some wound in the skin, e.g., Anthrax, tetanus.

(e)   Living creatures (especially insects) e.g., Cholera (through files), Malaria (through mosquitoes).

(f)    Direct contact, e.g. small pox, Venereal diseases

Immunity

Bacteria and microbes cause several diseases in man. The disease causing germs often release toxins, which are poisonous. Normally, our body is able to defend itself against most disease causing micrones with the help of WBC. Bacteria are engulfed and devoured by the WBC. Occasionally the number of bacteria far exceeds the capacity of the WBC to remove them. Many persons are able to resist diseases to a certain extent due to a chemical reaction in their blood, which makes them immune to a disease. The blood of this person produces substances called antibodies, which fight the invading organisms. Each kind of antibody can act only against one type of microbe. Different antibodies have different characteristics. The substance that causes the formation of antibodies is called the antigen. The foreign microbes or the toxins produced by them may act as antigens. The resistance of our body to a disease is called immunity.

Natural and acquired immunity

Some persons are immune to certain diseases from birth. These people are said to have natural immunity. Some people who have once suffered from a disease may not be affected again during their lifetime. The body retains adequate levels of antibodies for the protection against future infection. This is called acquired immunity. A person can develop immunity by treatment with appropriate antigens the immunity caused in an organism by such means is called Artificial or Acquired immunity. Edward Jenner was the first to discover a safe and effective means of producing artificial immunity against smallpox. In vaccination the host is deliberately infected with a disease-producing organism, the inoculated substance is called a vaccine. The vaccine against smallpox is produced by infecting calf or horse with the smallpox virus. The virus in the calf or horse becomes weakened. This weakened smallpox virus is collected as a vaccine and introduced into the human body. Since the virus is weak it is not able to cause a severe form of the disease in man. But the presence of the virus induces the body to produce antibodies and provide immunity against smallpox. Such immunity is called active immunity, the effect of which may last for several years or even throughout life. Immunity can also be gained in another way. An experimental animal like a horse is infected with disease producing microbes. The antibodies are produced in the blood of the horse. The serum of the horse containing the antibody is extracted and introduced into the human body. The human body utilise the readymade antibodies thus producing immunity, which is known as passive immunity. Allergy is also dependent on antibody formation. When the antigen antibody reaction occurs within the tissues instead of in the blood a severe allergic reaction is likely to occur. These reactions are characterised by local inflammation, as is Urticaria. Dust particles, pollen grains and many other substances function as antigens in allergic reaction.

Medicines

Medicines are chemical substances used for treatment of disease and for reducing the suffering from pain.

Chemical used to frequently classified according to their action.

Antipyretics

These chemicals bring down body temperature during high fever and the patient. Commonly used chemicals are aspirin, phenactin and paracetamol.

Analgesics

These drugs relieve pain. Aspirin and some other antipyretics act as analgesics certain narcotics, i.e. morphime, marijuana, codeine and heroin are also used as analgesics.

Antiseptics and Disinfectants

These chemicals kill or prevent the growth of microorganisms.

Antiseptics are applied to the living tissues, and this applicable to wounds, cuts, ulcers and diseased skin surfaces, and also used as deodorants & breath purifiers.

Disinfectants kill microorganisms that live in inanimate items like floor, instruments etc.

Phenol is used as both, 0.2% solutions of phenol as antiseptic and 1% solution of phenols as disinfectants.

Chlorine is used for making drinkable water by adding a concentration of 0.2 to 0.4 ppm.

Low concentration of sulphur dioxide is used as preservatives in squashes.

Bithional imparts antiseptic properties to the soap, and reduces undesirable odours from skin.

Tincture of iodine, is a powerful antiseptic.

Iodoform was widely used as an antiseptic powder.

Organic dyes such as gentian violet and methylene blue are used as antiseptic dyes.

Tranquilizers

Tranquilizers are substances that are used for the treatment of mental diseases, and act on central nervous system. They are constituents of the sleeping pills, and helping the patient by alleviating symptoms, which interferes with sleeping function of the brains.

Derivatives of the barbituric acid are known as tranquilizers since long times.

Equanil is too used in depression and hypertension.

Antibiotics

Antibiotics are chemicals produced by microorganisms (bacteria, fungi and molds) that stops or destroys the growth of other microorganisms.

Penicillin was the first antibiotic, obtained from the mold Penicillin notatum. It is used against large number of infections like pneumonia, bronchitis, sore throat and abcesses, caused by cocci, gram positive bacteria.

Streptomycin (produced from Straptomycetes) and tetracycline are used against diseases caused by gram-negative bacteria, which have penicillin resistant capability.

Streptomycin is effective against TB and while chloramphenicol for typhoid.

Broad spectrum antibiotics are effective against several different types of harmful micro organisms. These are tetracycline, chloramphenicol and others.

Penicillin

A narrow spectrum antibiotic is Penicillin. Penicillin is produced in commercial production by using the Penicillium chrysogenum and its various mutants. Its production involves and large-scale fermentation. The patient’s sensibility (allergy) is required before it is administered.

Ampicillin and amoxicillin are semi synthetic modifications of Penicillin.

Chloramphenicol

It is a broad spectrum antibiotic.

It is give orally and it is rapidly absorbed from the gastro-intestinal tract.

It is effective against typhoid, dysenetery, acute fever, certain urinary infections, meningitis and pneumonia.

Sulpha drugs

Sulpha drugs like sulphanilamide, sulphadiazine and sulpha guananidine act against micro organisms like anti-biotics.

Important tables

Mental Health and psychoactive drugs

Drugs in sports

Some important vaccines

National Immunisation schedule

venomous animals