CBSE Class 12 Biology Chapter 8 Human Health and Disease Revision Notes PDF

Preview

Summary

Biology study material for Exams...

Description

Health and Diseases The human body is an amazing creation. There are many systems within the same body that function so well in a well-coordinated and integrated manner. No wonder it took some time to really understand the functioning of the human body and other related aspects. Today we have a better understanding of what constitutes health which also includes mental health. Let us take a look.

What is Health? Why Is It Important? According to the World Health Organization, Health is defined as the state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. Health also reflects the metabolic and functional efficiency in living organisms. Health is considered as a basic parameter to life. There are many things that can affect the health of the living organism, including the physical state of the body as well as the mind and the mental state. Being healthy equates to many positive attributes. It means more efficiency, more productivity at work, a better understanding of the environment as well as better longevity.

A healthy body is not only a good sign for the self but also for the economy. That is because if the population of a country is healthy and energetic, then the productivity goes up, leading to economic prosperity. Another aspect of good health is that it leads to lower infant and maternal mortality. Browse more Topics under Human Health And Diseases

● Types of Diseases ● Immune System ● Antigen and Antibody ● Interferons and Lymphoid Organs ● Disorders of Immune System ● Vaccines and Immunisation ● Cancer ● Drugs and Alcohol Abuse

Mental Health

To maintain good health a variety of factors play a role. Some these include a well-balanced nutritious diet, regular exercise, and healthy lifestyle practices etc. apart from meditation or yoga that helps in maintaining a better mental health. In recent times we have understood that mental health of a person is just as important as physical well being. In India, we have recently passed the Mental Health Act, 2017 which aims at providing health services to those suffering from mental illnesses and remove the stigma associated with it.

Diseases The human body in its entirety should be able to function properly. If any of the organs or organ systems do not function properly, giving to rise to signs and symptoms of not being well, then it is said that the

state of health is not good. However, the human body has this ability to repair itself and attack any foreign body entering it, thanks to the specialized functions that are performed within the body. But, there are times when the body is invaded by microbes or microorganisms, that disrupt the effective functioning of the whole system. These microbes cause infection and cause a condition in the body that impairs the functioning of the infected organ/organ system. This condition is called a disease. Any disease is generally accompanied by signs and symptoms that give us an indication that all is not well with the functioning of the bodily organs and systems. Thus these symptoms are used as indicators which help in diagnosing the type of disease. Diseases can be of different types. Some may be passed on from one person to the other, while other diseases are not passed on to other people. Some diseases can be life-threatening and even fatal, resulting in death, if proper medication or treatment is not taken on time.

Solved Questions For You

Q: Health is a. Weight of body according to height b. Absence of disease or infirmity c. State of complete physical mental and social well being d. None of the above

Ans: The correct option is “C”. Health is defined as a state of complete physical, mental and social well-being. It depends on three parameters physical, mental and social. It is a dynamic condition resulting from a body’s constant adjustment and adaptation in response to stresses and changes in the environment for maintaining an inner equilibrium called homeostasis.

Types of Diseases Any disorder or malfunctioning of the body or mind that destroys good health can be called as a disease. The status of health of the body in a disease is said to be compromised. A disease can be caused due to a variety of reasons. Every disease has characteristic symptoms through which we can identify the types of diseases.

Classification of Diseases – Types of Diseases According to a very broad classification, diseases can also be classified under the following – physical diseases, mental diseases, infectious diseases, non- infectious diseases, deficiency diseases, inherited diseases, degenerative diseases, social diseases, self-inflicted diseases. Depending on certain characteristics, diseases can also be classified as an acute disease where the onset of the disease is sudden, lasts for a short time, with rapid changes; and chronic diseases  where the effects of the disease can last for months or years.

Even though the types of diseases can be classified very broadly, the classification of diseases into infectious and non-infectious diseases is considered very apt. Infectious diseases can be easily transmitted from

one person to the other while the non-infectious disease cannot be transmitted. Browse more Topics under Human Health And Diseases

● Health and Diseases ● Immune System ● Antigen and Antibody ● Interferons and Lymphoid Organs ● Disorders of Immune System ● Vaccines and Immunisation ● Cancer ● Drugs and Alcohol Abuse

What Causes Cancer? Any organism or m  icroorganism that causes a disease is called as a pathogen. A specific disease is caused by a specific pathogen. The infectious diseases are often transmitted by pathogens. These diseases can be spread through contact or proximity, either through air, water, soil or through vectors.

Pathogens can be of different types. They can be either bacteria   or virus or fungi or a protozoan   or even a helminth. Most of the parasites that are found are pathogens as they cause many diseases in humans. Some of the bacterial diseases  are Syphilis, Pneumonia, Tetanus, and Tuberculosis. Examples of diseases caused by a virus are Chickenpox, Small Pox, Measles, Polio. Fungal infections include Ringworm infection, Athlete’s foot, Yeast infections etc. Malaria is a disease caused by an organism belonging to Protista. Diseases caused by helminths include Ascariasis, Taeniasis etc.

Some Types of Diseases Explained Briefly Typhoid

It is caused by the bacterium, Salmonella typhi. The pathogen enters the body through contaminated food and water. High fever, weakness, stomach pain, headache, constipation, loss of appetite are the symptoms of this disease. The Widal test confirms this disease. Disorders of Immune System Pneumonia

It is caused by Streptococcus pneumoniae and Haemophilus influenzae bacteria. This disease affects the lungs. The alveoli of the lungs get infected and filled with fluid, causing respiratory problems. This is a disease that is acquired by inhaling the droplets or aerosols that are released by an infected person. The main symptoms include chills, fever, headache, and cough. Common Cold

The common cold is generally caused by a group of viruses called rhinovirus. The respiratory passage and the nose are commonly infected here. Nasal congestion, discharge, sore throat, cough, hoarseness, tiredness, are some of the associated symptoms of common cold, that can last for up to seven days.

This infection is transmitted when an infected person releases the droplets either through a cough or sneeze. These droplets can be either inhaled directly by other people or can be transmitted with the help of contaminated objects. How does MRI Scanner Work? Malaria

It is a disease caused by a protozoan called Plasmodium. There are different types of malaria caused by different types of species of Plasmodium. Some of the species are Plasmodium vivax, Plasmodium malaria, Plasmodium falciparum. Malignant and fatal malaria is caused by Plasmodium falciparum. The female Anopheles mosquito is the vector that carries the infectious form of the pathogen into the human body. Therefore, the malarial parasite has two hosts, i.e. human and mosquito to complete its life cycle. When an infected female Anopheles mosquito bites a human, it transfers the sporozoites of the Plasmodium parasite. These parasites multiply in the liver cells and then attack the RBCs, rupturing them.

When RBCs rupture, they release a toxic substance called haemozoin. This toxic substance is responsible for the classic symptoms of malaria – fever associated with chills. The spread of the disease can be controlled by killing the vector, mosquito.

Amoebiasis

Entamoeba histolytica causes Amoebiasis. It is a protozoan parasite that is present in the large intestine of a human. Amoebiasis is also called as amoebic dysentery. This disease is transmitted by houseflies that carry the parasite from the contaminated faeces of an infected person to any food product, thereby contaminating it. The symptoms include abdominal pain, cramps, constipation, stools with excess mucous etc. Ascariasis

It is a disease that is caused by a helminth, Ascaris lumbricodes, also called the roundworm. It is an intestinal endoparasite found in humans. Muscular pain, internal bleeding, fever, anaemia, intestinal passage blockage are some symptoms of this disease. The infection is spread by contamination of soil, water, plants, etc. as the eggs of the parasite are excreted out through the faecal matter. Filariasis

Also called as elephantiasis, this disease is characterized by the inflammation of the affected organs. Even genital organs can get affected by this disease. Wuchereria bancrofti and Wucheria malayi are the filarial worms that are responsible for causing this disease. The female Culex mosquito acts as the vector for transmitting the pathogen. Fungal Diseases

Ringworm infection is caused by Fungi. Some of the Fungi that cause this infection are Microsporum, Trichophyton, and Epidermophyton. It is a very common infectious disease that is characterized by intense itching and dry, scaly lesions on the skin, nails, and scalp. Moisture and heat are the favourable factors that help the fungi grow.

Preventive Measures The different types of diseases, especially, infectious diseases can be prevented by taking the right measures. Personal and public hygiene play an important role here. Eradication of vectors that carry the pathogens is also an effective preventive measure. Vaccinations also help in tackling many infectious diseases. Mental Health and the factors that affect it.

Solved Questions For You Q: Blackwater fever is also known as which of the following? a. Yellow Fever b. Scarlet Fever c. Aestivo-autumnal malaria d. Encephalitis

Ans: The correct option is “C”. Blackwater fever, also called malarial hemoglobinuria or ‘aestevo autumnal malaria’ is a complication of malaria in which the RBCs burst in the bloodstream, (hemolysis)

releasing haemoglobin directly into the blood vessels and into the urine, leading to kidney failure.

Immune System The immune system of the body is the essential aspect of our survival. If an immune system is absent then the body is very easily susceptible to infections caused by bacteria, virus, and various other pathogens. Let us learn about this unique system.

Uniqueness of the Immune System The human immune system is very unique. It is spread throughout the body, involving several types of cells, tissues, organs etc. A significant characteristic feature of this immune system is that it can distinguish between the body tissue and a foreign tissue. Even dead and faulty cells can be recognized by the immune system, which is cleared away from time to time by the immune system. The immune system also has a role to play in allergic reactions, organ transplantation, and autoimmune diseases. It can be said that the immune system is majorly responsible for keeping us in good health.

Human Immune System

Organs of the Immune System (Source – Wikimedia Commons)

The human immune system consists of tissues, c ells, soluble molecules like antibodies and lymphoid organs. The white blood cells called the leucocytes  have a significant role as they seek out to destroy the disease-causing organisms. These leucocytes are stored in different locations in the body including the spleen, bone marrow, and thymus. And therefore these organs are called as the lymphoid organs. The leucocytes are also present in the lymph nodes of the body. The bone marrow is considered as the main lymphoid organ. It produces all the blood cells including the lymphocytes. The thymus is

an organ that is present near to the heart, beneath the breastbone. It is very large at the time birth and gradually reduces in size. In the bone marrow and the thymus, the immature lymphocytes differentiate and become antigen sensitive lymphocytes. Once they are mature, they migrate to the other secondary lymph organs such as the spleen, lymph nodes, tonsils, appendix, and Peyer’s patches of the small intestine. The secondary lymphoid organs are the sites where the lymphocytes interact with the antigen and then proliferate to become effector cells. The spleen is a large organ that contains lymphocytes and phagocytes. It filters the blood and traps the microorganisms that are blood borne. Lymph nodes are small structures that are present in the lymphatic system of the body. They also trap the microorganisms that are present in the lymph or tissue fluid. The antigens in the lymph activate the lymphocytes and cause the immune response.

Solved Questions For You

Q: Which lymphoid organ is large in size at birth, but gradually reduces in size? a. Spleen b. Thymus c. Pituitary d. Thyroid

Ans. The thymus is a lymphoid organ that is large in size at the time of birth. By the time a person reaches the age of puberty, it shrinks in size and becomes a small organ. Q: To which type of barriers under innate immunity, do the saliva in the mouth and the tears from the eyes belong?

a. Physiological Barriers b. Physical Barriers c. Cellular Barriers d. All of the above

Ans: The correct option is “A”. The immune system provides both the types of immune response innate and acquired immune responses. Innate immunity occurs naturally due to genetic factors or physiology. It is a native immune response that present by birth. It provides physical barrier such as skin, Physiological barriers such as pH of the stomach, bile juice, saliva and tears, cellular barriers such as leucocytes, macrophage cell, and cytokine barrier.

Antigen and Antibody When you read about antigen and antibody, you will begin to understand that these have something to do with the immunity in the body. In the field of microbiology and immunology, the antigen-antibody complex has a major role. Let us take a detailed look.

What is an Antigen? Antigens are substances that stimulate the i mmune system to produce antibodies. Each antigen has a distinct surface feature or epitope. Thus there is a resultant effect of a specific response. Antigens could be anything like a pathogen or bacteria or fungi or even virus. They cause diseases or allergic reactions. Antigens are generally proteins. But they can be lipids, carbohydrates or nucleic acids. Antigens can be of three types – Exogenous, endogenous and autoantigens. Antigens can also be foreign bodies that stimulate the immune system of the body. Even pollen and spores can be antigens. To summarise in a nutshell, antigens are the harmful germs or pathogens or other foreign substances that pose a threat and disrupt the normal functioning of the body. And in order to stop this disruption, the body produces an antibody to protect itself, thereby destroying the antigens. Browse more Topics under Human Health And Diseases

● Health and Diseases ● Types of Diseases

● Immune System ● Interferons and Lymphoid Organs ● Disorders of Immune System ● Vaccines and Immunisation ● Cancer ● Drugs and Alcohol Abuse

What is an Antibody? An antibody is an immunoglobulin. It is a Y shaped molecule which is basically a protein that is produced by the B cells of the immune system. Antibodies are produced in response to the exposure to antigens. An antibody has a paratope that can recognize the epitope that is present on the surface of the antigen. Both the antigen and antibody act like a lock and key mechanism. With the help of this binding, the antigens are eliminated from the body. This occurs either through direct n eutralization or with the help of tagging of other arms of the immune system.

There are five kinds of antibodies, such as Immunoglobulins M, G, E, D and A. An antibody is a serum protein that is generally found in blood.

(Source – Interactive biology)

Structure of Antibody

As mentioned above, an antibody is a protein molecule in the shape of Y. It has four polypeptide chains. Two are the light chains that are identical and short and the other two are identical and longer and are called the heavy chains. The light chains are represented as L and the heavy chains are represented as H. So, while representing an antibody, it is represented as H2 L2.

Both the heavy chains and light chains are held together by disulfide bonds. Both these chains also have two regions called the distinct region and the variable region. It is the variable region of the antibody that sees the action happening. Here the lock and key mechanism occur along with the antigen that has adhered to the antibody. Antigens and Antibodies – Their role in Vaccinations

Antigens and antibodies have a significant role to play in vaccines. They are present in vaccines so that they can stimulate the B lymphocytes present in the immune system. Once these lymphocytes are stimulated, they respond and produce plasma cells which secrete the specific antibodies for that specific disease. There are some B cells that become memory cells which help in recognizing any future exposure to the disease. So, ultimately, this helps in the faster production of antibodies. These antibodies work efficiently and bind themselves to the antigens and thereby eliminate the disease.

Solved Questions For You Q: What are the different types of antibodies present? Write a few lines. Ans. The different types of antibodies that are present are as follows: ● Immunoglobulin A – It protects against gastrointestinal and respiratory problems. ● Immunoglobulin D – It activates the B cell, after an interaction with the antigen. ● Immunoglobulin E – It controls allergic r eactions. ● Immunoglobulin G – They stimulate phagocytes.

● Immunoglobulin M – It is the largest antibody and helps in the activation of B cells.

Interferons and Lymphoid Organs The human immune system is more like a defence mechanism of the body which is essential for our survival and helps us fight many diseases and infections. The immune system is made up many special cells, tissues  , organs, proteins   etc. Interferons and Lymphoid Organs are part of the I mmune System of the human body.

Interferons Interferons help in protecting us against microorganisms and germs that cause diseases thereby keeping us healthy. With the help of the immune response, the immune system attacks the organisms that invade the body. But, when the immune system of the body fails for some reason, then the body is prone to infections. The ability of the body to fight the disease-causing organisms due to the working of the immune system is called as Immunity. It has great

importance in medicine because it probes into the various causes of diseases due to lack of immunity. Browse more Topics under Human Health And Di...