HUMAN HEALTH AND DISEASE (NOTES)

  ATS COACHING CLASSES
  REVISION NOTES                          
  HUMAN HEALTH AND DISEASE

Health: The state of complete physical, mental and social well beings is called health. Health simply does not simply mean disease-free condition or physical fitness. 

Health is affected by: 

a. Genetic disorders – the defect which child inherits from it parents. 

b. Infection from microbes or other organisms. 

c. Lifestyle- includes food and water we take, exercise and rest.

 

We can maintain good health by:

 (i) A good balanced diet. 

(ii) Maintaining personal hygiene.

 (iii) Do regular exercise.

 (iv) Spreading awareness about the disease.

 (v) Getting Immunized against the infectious disease.

 (vi) Disposing waste in a proper way.

 (vii) Controlling vectors Disease: these are of two types: 

1. Infectious diseases: Diseases that get easily transmitted from one person to another, are called infectious diseases. AIDS, common cold, malaria are some examples. 

2. Non-infectious diseases: Diseases that cannot be transmitted from one person to another, are called non infectious diseases. cancer, hypertension, diabetes are some examples. Diseases can be caused by bacteria, viruses, fungus, protozoa, and helminthiasis, they are grouped under the category of pathogen.

Plasmodium: Life Cycle

 Plasmodium enters the human body as microscopic sporozoites from the bite of an infected female anopheles mosquito and multiplies within liver cells. Later, the RBCs are attacked, leading in rupture and the production of a poisonous chemical, haemozoin, which is responsible for high fever and chills that re-occur every three to four days. Malaria parasites require two hosts to complete their life cycle: humans and anopheles’ mosquitos. Female anopheles is the disease's vector to humans.

 Let’s have a look at the life cycle in detail: 

o When a female Anopheles mosquito bites an infected person, these parasites enter the mosquito’s body and undergo further development. 

o The parasites multiply within them to form sporozoites (infectious stage) that are stored in their salivary glands. 

o When these mosquitoes bite a human, the sporozoites are introduced into his/ her body, thereby initiating the events mentioned above.

Immunity: 

Immunity refers to the ability of host cells to resist disease-causing microorganisms through the immune system. 

Immunity is classified into two types: 

1. Innate immunity: The immunity that an individual gets from birth is called innate immunity. It is a non-specific type of defense. It has four types of barriers:

 

• Physiological barriers: e.g. acid in the stomach wall, saliva, and tears in the eyes.

 • Physical barriers: e.g. skin, the mucus coating of the epithelium lining of the respiratory tract, gastrointestinal tract, and the urogenital tract.

 

• Cellular barriers: Certain types of leukocytes (WBC) of our body like polymorpho-nuclear leukocytes (PMNL-neutrophils) and monocytes and natural killer (type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes. 

• Cytokine barriers: Virus-infected cells secrete proteins called interferons which protect noninfected cells from further viral infection.

2. Acquired Immunity: Pathogen-specific defence is distinguished by memory. When our body first meets a virus, it creates a response known as the initial response that is of modest intensity. Due to the memory of the initial contact, subsequent encounters with the same virus create a significantly heightened response known as the secondary response or anamnestic response. Primary and secondary reactions are carried out with the assistance of B- and T-lymphocytes. B-lymphocytes create an army of proteins known as antibodies, each of which has two light and two heavy chains.

 The B-lymphocytes show humoral immune response and the T-lymphocytes show cellmediate immunity. 

Antibody: Structure 

IgA, IgM, IgE and IgG are various types of antibodies produced by our body.

 Each antibody molecule is made up of four polypeptide chains, two of which are long and are known as heavy chains, and two of which are short and are known as light chains. Because both are organised in the form of a 'Y,' an antibody is denoted as H2L2.

Immunity is again of two types as per antibodies produced by the body:

 1. Active immunity: The body generates its own antibodies against antigens. Active immunity is slow and takes time to give its full effective response. 

2. Passive immunity: When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive. 

E.g colostrum secreted by mother in the initial days of lactation contains numerous IgA antibodies, it protects the baby during initial days of lactation from infections. 

Note: The body is able to differentiate ‘self’ and ‘nonself’ and the cell-mediated immune response is responsible for the graft rejection.

Autoimmunity: The human immune system can differentiate between self and alien molecules or foreign entities. Sometimes, the body attacks its own cells for unclear reasons, the reason can be genetic also. This causes harm to the body and is known as auto-immune illness. E. g rheumatoid arthritis.

Vaccine: In vaccination, a preparation of antigenic proteins of pathogen or inactivated/weakened pathogen (vaccine) are introduced into the body. The antibodies produced in the body against these antigens would neutralise the pathogenic agents during actual infection. The vaccines also generate memory – B and T-cells that recognise the pathogen quickly on subsequent exposure and overwhelm the invaders with a massive production of antibodies. 

Passive Immunisation: Sometimes a person gets infected with some deadly microbes to which quick immune response is required E.g tetanus.

 In such case, we need to directly inject the preformed antibodies, or antitoxin (a preparation containing antibodies to the toxin). Even in cases of snakebites, the injection which is given to the patients, contain preformed antibodies against the snake venom. This type of immunisation is called passive immunisation.

Allergy: Allergy is defined as an excessive immune system reaction to particular antigens in the environment. Allergens are substances that cause such an immunological reaction.

 IgE antibodies are created as a result of this. Allergies are caused by the mast cells secreting substances such as histamine and serotonin.

 Lymphoid Organs: The lymphoid organs, tissue, cells, and soluble chemicals such as antibodies comprise the human immune system.

 Lymphoid organs are the sites of lymphocyte formation, maturation, and proliferation. The bone marrow and thymus are primary lymphoid organs where immature lymphocytes differentiate into antigen-sensitive lymphocytes. Lymphocytes travel to secondary lymphoid organs such as the spleen, lymph nodes, tonsils, Peyer's patches of the small intestine, and the appendix after maturation. They serve as locations for lymphocytes to engage with antigens. The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells.

Bone Marrow:  The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.

 

Thymus: The thymus is a lobed organ located near the heart and beneath the breastbone. The thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size. 

Note: Both bone-marrow and thymus provide microenvironments for the development and maturation of Tlymphocytes.

 Spleen: The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes. It acts as a filter of the blood by trapping blood-borne microorganisms. Spleen also has a large reservoir of erythrocyte.

 Lymph Nodes: The lymph nodes are small solid structures located at different points along the lymphatic system. Lymph nodes serve to trap the micro-organisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response. 

MALT: There is lymphoid tissue also located within the lining of the major tracts (respiratory, digestive and urogenital tracts) called mucosa-associated lymphoid tissue (MALT). It constitutes about 50 per cent of the lymphoid tissue in human body. 

AIDS: The first case of AIDS (Acquired Immuno Deficiency Syndrome) was recorded in the year 1981. It is caused by retrovirus HIV (Human Immunodeficiency virus). The HIV virus spreads primarily through-

 (i) Sexual intercourse with an infected individual. 

(ii) The use of infected blood and blood products in transfusions. 

(iii) Sharing contaminated needles, as in the case of intravenous drug users. 

(iv) From an infected mother to her kid via the placenta. Physical contact does not transfer AIDS/HIV. It is only transmitted by bodily secretions. There is usually a time difference between infection and onset of symptoms, which can range from 5 to 10 years. ELISA is an AIDS diagnostic test (Enzyme-Linked Immuno-sorbent assay). The therapy of this condition with anti-retroviral drugs is only partially effective, extending life but not preventing death.

Cancer: In human body, cell growth and differentiation is a highly controlled process. In cancer cells, there is a breakdown of these regulatory mechanisms.

Tumor: When the cancerous cells continue to divide giving rise to a mass of cells then it is called tumor. It is again of two types:

 1. Bengian tumor: it remains atthe place where is has arose, rate of growth is slow, causes minimum damage to the a body, it has no latent stage, no metastasis is there and the last it is non-cancerous. 

2. Malignant tumor: it spreads to other parts of the body, shows vigorous growth, show a latent stage, there is metastasis and it is cancerous.

 

Causes of cancer: It is caused by: 

1. Carcinogens are physical, chemical, and biological factors that can cause transformation of normal cells into cancerous neoplastic cells. 

2. Oncogenic viruses have viral oncogenes, which are genes that cause cancer. In normal cells, many genes known as cellular oncogenes (c-onc) or proto oncogenes have been found that, when activated under particular conditions, can lead to oncogenic transformation of the cells.

Detection and diagnosis: Biopsy and histological examination of tissues, blood and bone marrow tests for elevated cell counts are used to identify cancer. Internal organ tumors benefit greatly from radiography, CT (computed tomography), and MRI (magnetic resonance imaging). 

Treatment: it may be treated by radiation; immunotherapy may be given or may be removed surgically. Note: Tumor cells have been shown to avoid detection and destruction by immune system. Therefore, the patients are given substances called biological response modifiers such as α-interferon which activates their immune system and helps in destroying the tumor.

Drugs and Alcohol abuse

 Most common drugs that are abused are: 

1. Opioids: Opioids are medications that get attach to opioid receptors in our central nervous system and gastrointestinal tract. Heroin, sometimes known as smack, is a white, odourless, bitter crystalline substance, it is chemically diacetylmorphine and is derived from the latex of the poppy plant (Papaver somniferum). Heroin is a depressant that slows down biological functioning and is commonly snorted or injected.

 Note: Morphine is a very effective sedative and painkiller, and is very useful in patients who have undergone surgery.

2. Cannabinoids: Cannabinoids are a class of substances that bind to cannabinoid receptors in the brain. The inflorescence Cannabis sativa is used to extract natural cannabinoids. Some of the examples of cannabinoids are marijuana, hashish, charas, and gangja are among them. They are renowned for their effects on the circulatory system of the body and are commonly administered through inhalation and oral consumption.

3. Coca alkaloids: Coca alkaloid/cocaine is derived from the South American coca plant Erythroxylum coca. It disrupts the transit of the neurotransmitter dopamine. Cocaine, often known as coke or crack, is typically snorted. It has a strong effect on the central nervous system, causing euphoria and enhanced vitality.

 Note: Some other plants with hallucinogenic properties are Atropa belladona and Datura. 

Nicotine: Tobacco contains a large number of chemical substances including nicotine, an alkaloid. Nicotine stimulates adrenal gland to release adrenaline and nor-adrenaline into blood circulation, both of which raise blood pressure and increase heart rate. Smoking is associated with increased incidence of cancers of lung, urinary bladder and throat, bronchitis, emphysema, coronary heart disease, gastric ulcer, etc. Tobacco chewing is associated with increased risk of cancer of the oral cavity. Smoking increases carbon monoxide (CO) content in blood and reduces the concentration of haembound oxygen. This causes oxygen deficiency in the body.

Adolescence: the period when a child becomes mature is called adolescence. The is 12-18 years. Some of the adolescence get in drug abuse during this age. 

Causes of drug abuse: it can be due to stress, companionship, excitement or simply experimentation. 

Harmful effects of drug abuse: people taking drugs can become careless, mischievous, violent, can go in depression, can isolate themselves also. 

Dependence: Dependence is the body's predisposition to exhibit a distinct and unpleasant withdrawal experience when a regular dose of drug/alcohol is abruptly removed, it includes anxiety, shakiness, nausea, and sweating.

Counselling, education, parents help, professional help can help in prevention and control.