SSC Biology Diseases Diseases and their Defence Mechanism

Introduction

• Health is a state of complete physical, social and mental well-being and not merely the absence of disease or infirmity.
• Disease is any condition which interferes with the normal structure and function of the body that is manifested by a characteristics sets of symptoms and sign.

• Bacteriol Diseases
• Typhoid: Typhoid is caused by Salmonella typhi. Typhoid spreads through food, milk and water contaminated with intestinal discharges either directly or through flies and personal hygiene. Typhoid is diagonsed with widal test.
• Pneumonia: It is caused by Streptococcus pneumonia or Haemophilus influenza. It infects alveoli of lungs and spread by coughs, sneezes, by sharing drinking glasses and eating utensils with an infected person and contact with used tissue or handkerchiefs.

• Viral Diseases
• Rhinoviruses causes one of the most infectious disease called common cold. Rhinovirus is spread from one person to another by hand to hand contact or from one person sneezing close by another person.

• Protozoan Diseases

Malaria: It is caused by Plasmodium species & spread through female Anopheles mosquito. Primary host are female mosquito of genus Anopheles and humans acts as intermediate host.

• Malaria result in anaemia, toxaemia and splenomegaly (enlarged spleen).
• Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. Plasmodium sporozoites enters the bloodstream and travel to liver where they divide repeatedly & other attack the red blood cells resulting in their rupture.

• Amoebic Dysentery or Amoebiasis
• It is caused by Entamoeba histolytica. It is a protozoan parasite in the large intestine of human.

Helminthic Diseases

• Filariasis
• Filariasis is caused by Wuchereria bancrofti.

• Fungal Diseases
• Fungi cause’s diseases and these are known as mycosis.
• Microsporum, Trichophyton and Epidermo-phyton are responsible for ringworms, which is characterized by appearance of dry scaly lesions of the skin, nails and scalps.

• Sexually Transmitted Diseases
• Sexually transmitted diseases (STDs) are a group of communicable diseases that are transmitted mainly by sexual contact. STDs are caused by a wide range of bacterial, viral, protozoal and fungal agents.

• Diabetes mellitus
• It is caused by the deficiency of insulin hormone and is characterized by excessive concentration of sugar in the blood and urine. Diabetes insipidus, on the other hand, is characterized by excessive urination, urine being sugar- free and is caused by the deficiency of ADH.

Cancer

• Cancer is not inheritable.
• The non-regulated growth of the cells that accompanies cellular transformation produces tumours or neoplasms, each tumour being the product of proliferation of a single abnormal cell. Tumours are of two types - benign and malignant.
• Benign tumour cells is a large localized mass of abnormal tissue enclosed in connective tissue which does not spread to distant sites.
• Malignant tumour cells are cancer cells that spread to and take up residence in neigh bouring tissues - a condition called metastasis.
• Agents that cause cancers are called carcinogens. UV radiations, smoking, mustard gas, soot, viruses, coal tar, aflatoxins and industrial pollutants are known to be carcinogenic.
• Cancer can be detected by

-   biopsy and histopathological studies of the tissue.

-   blood and bone marrow tests for increased cell counts as in Leukaemia,

-   use of techniques like radiography, magnetic resonance imaging (MRI) and computed tomography (CT) for cancer of internal organs.

• Treatment of Cancer
• Therapy used in the treatment of cancer are surgery, radiotherapy, chemotherapy, immuno-therapy, hormonal therapy, etc.

AIDS

• AIDS

AIDS is caused by Human Immunodeficiency Virus (HTV) which is retrovirus.

• Life Cycle of HIV
• The virus after getting into the body of a person, enters the macrophages.
• The person becomes easily infected by bacteria like mycobacterium, viruses and even parasites like Toxoplasma.
• The person is unable to protect himself/herself against any infection.
• AIDS is diagnosed by ELISA (Enzyme Linked Immunosorbent Assay).

• Prevention of AIDS
• World Health Organization (WHO) has started a number of programmes to prevent spreading HTV infection; some such steps include:

-   ensuring use of disposable needles and syringes.

-   checking blood for HIV.

-   free distributions of condoms and advocating safe sex.

-   controlling drug abuse.

-   Promoting regular check-up for HIV in susceptible populations, etc.

• Treatment with anti-retroviral drugs is only partially effective; they can only prolong the life of the patient and cannot prevent death.

Immunity

• Immunity

The term immunity refers to the specific resistance exhibited by the host towards infections by micro-organisms (pathogens) and their products.

• Innate or Natural Immunity
• Innate immunity is developed in an individual without having the disease or immunization, e.g., recreation of sweat glands contain certain chemical substances which prevent the entry of micro-organisms.
• It is present from birth.
• It is the general defence of body including the following four mechanism —

(i) Phagocytosis of invaders by leucocytes and macrophages (called cellular barrier).

(ii) Resistance of skin to invading micro-organisms (called physical barrier).

(iii) Destruction of micro-organisms swallowed with food by the HCl of gastric juice & by digestive enzymes and tear from eye (coiled physiological barriers).

(iv) Virus infected cells secrete proteins (called interferons) which protect non-infected cells from further viral infection (cytokine barriers)

• Acquired Immunity
• It is a third line defence and developed by an animal in response to a disease caused by infections of microbes.
• The resistance against infectious disease that an individual acquires during life is known as acquired immunity.

• Antibody Mediated Immunity
• B cells produce specialized proteins called antibodies (immunoglobulin) which are glycoproteins.

• Classification of Antibodies:

(a) Ig A - Protects from inhaled or ingested pathogens.

(b) Ig D - Present on lymphocyte surface as receptors, activation of B cells.

(c) Ig E - Mediator in allergic response.

(d) Ig G - Stimulation of phagocytes and complement system, passive immunity to foetus.

(e) Ig M - Activation of B cells.

• Immunization
• Inoculation of vaccines to prevent diseases is called immunization.
• Vaccines are preparations of living or killed micro-organisms or their products. Vaccines are of two types — live vaccines and killed vaccines.
• Genetic vaccines involve one or more genes from diseases carrying agent (pathogen) and splicing these gene into plasmids (closed rings of DNA). These rings are then delivered into small groups of cell, often by infection into muscle cells or by propulsion into via so called 'gene gun’.
• Allergy and Autoimmunity
• Allergy is an important side effect of immunity.
• Autoimmune disease result when the immune system attack and destroys 'self-cells and molecules. Eg., rheumatoid arthritis.
• Drugs and Alcohol Abuse

Major groups of psychotrophic drugs, their examples and effects