Karnataka 2nd PUC Biology Notes Chapter 8 Human Health and Disease

Health and Disease

→ Health can be defined as a stage of complete physical, mental and social well being.

→ Health increases the longevity of people.

→ It reduces infant and maternal mortality.

→ Healthy people are more efficient to work and this increases the productivity and economic • prosperity.

→ The factors that are very-important to maintain good health are :

  • Balanced diet
  • Personal hygiene and
  • Regular exercise.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

→ Good health can be achieved by the following:

  • Awareness about diseases and their effects on different bodily functions.
  • Vaccination/immunisation against infectious diseases.
  • Control of vectors.
  • Proper disposal of wastes/excreta.
  • Consumption of clean food and drinking water.

→ Health is affected by :
(a) Genetic disorders,
(b) Infections,
(c) Life style including food and water, rest, excercise and habits.


  • Diseases can be broadly classified into two types: (i) Infectious diseases and (ii) Non-infectious diseases.
  • The differences between them are as follows :
Infectious diseases  Noninfectious diseases
These are the diseases which are easily transmitted from one person to the other. These are the diseases which are not transmitted from one person to the other.
They are caused by pathogens. They Occur due to hereditary factors, deficiencies, habits, etc.
  • Some infectious diseases like AIDS and Hepatitis-B are fatal.
  • Cancer among non-infectious diseases, is the major cause of death.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

1. Common Infectious Diseases:

→ Depending on the pathogen, infectious diseases are as follows :

2nd PUC Biology Notes Chapter 8 Human Health and Disease 1
→ These pathogens enter our body by various means (direct contact, droplet infection, contaminated food and water, etc.), multiply there and interfere with the normal vital activities, resulting in morphological and functional disorders.

2. Viral Diseases:

(a) Common cold:
→ It is caused by the rhino viruses.

→ These viruses infect the nasal and respiratory passages, but not the lungs.

→ Its symptoms include:

  • Nasal congestion and discharge,
  • Sore throat
  • Cough,
  • Headache
  • Tiredness and
  • Hoarseness which lasts for 3-7 days

It spreads by,

  • Droplets released during cough and sneezing by an infected person and
  • Contaminated objects/articles.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

3. Bacterial Diseases:

(a) Typhoid :
→ It is caused by Salmonella typhi. The infection is by contaminated food and water. The pathogen enters the small intestine and then the other parts through body fluids. Its symptoms include:

  • Sustained high fever (103 °-104°F),
  • Stomach pain
  • Loss of appetite,
  • Constipation and
  • Headache.

→ Intestinal perforation leading to death may occur in severe cases.

→ Typhoid can be confirmed by widal test.

(b) Pneumonia:
→ It is caused by Streptococcus pneumoniae and Haemophilus influenzae.

→ They infect the alveoli of lungs, where the alveoli become filled with a fluid resulting in severe difficulty in breathing / respiration.

→ The symptoms include:

  • fever,
  • headache,
  • cough and
  • chills.

→ In severe cases the lips and fingernails may turn greyish to bluish.

→ Infection is by

  • droplets from an infected person and
  • sharing the contaminated articles.

4. Protozoan Diseases:

(a) Malaria:
→ It is caused by different species of Plasmodium, which are P. malariae, P. vivax and P. falciparum.

→ P. falciparum causes the most serious malignant malaria.

→ The infection is through the bite of female Anopheles mosquito, that transfers the sporozoites of Plasmodium.

→ The life-cycle of the pathogen is as follows :

→ The sporozoites enter the body, reach the liver through blood and multiply within the liver cells.

→ Such liver cells burst and release the parasites into the blood.

→ Then they attack RBCs, multiply and cause their rupture.

→ The rupture of RBCs is associated with the release of a toxin called haemozoin, which is responsible for the high recurring fever and chill/shivering.

→ Sexual stages (gametocytes) develop in the fed blood cells.

→ The parasite then enters the female Anopheles mosquito along with the blood when it bites the infected person.

→ Further development occurs in the stomach wall of the mosquito.

→ The gametes fuse to form a zygote.

→ The zygote undergoes further development in the body of the mosquito to form sporozoites. Sporozoites are transported to and stored in the salivary glands of mosquitoes and are transferred to a human body during the bite of the mosquito.

→ Treatment involves the use of chloroquines.

→ The disease can be controlled by eradicating mosquitoes and avoiding mosquito bite by using mosquito repellents, mosquito nets, etc.

2nd PUC Biology Notes Chapter 8 Human Health and Disease 2

2nd PUC Biology Notes Chapter 8 Human Health and Disease

(b) Amoebic Dysentery (Amoebiasis):

→ It is caused by Entamoeba histolytica.

→ Infection is through contaminated food and water.

→ The pathogen resides in the large intestine.

→ Its symptoms include:

  • Abdominal pain and cramps.
  • Stools with excess mucus and blood clots.
  • Constipation alternating with diarrhoea.

→ Houseflies act as mechanical carriers and transfer the parasite from the faeces of infected : person to the food articles and water.

5. Fungal Diseases

(a) Ringworms
→ These are caused by fungi like Microsporum, Epidermophyton and Trichophyton.

→ The symptoms include:

  • dry scaly lesions on skin, nails and scalp.
  • lesions accompanied by itching.

→ Ringworms are generally acquired ffom%oil or by direct contact with the contaminated j articles used by the infected persons.

6. Helminthic Diseases:

(a) Ascariasis:
→ It is caused by Ascaris lumbricoides. (round worm).

→ Its symptoms include:

  • Blockage of intestinal passage,
  • Anaemia,
  • Abdominal/muscular pain,
  • Internal bleeding,
  • Nausea and
  • headache.

→ Infection is through contaminated vegetables, fruits and water as eggs of the parasite, excreted by the infected persons contaminate soil, plants and water.

(b) Filariasis/Elephantiasis
→ It is caused by Wuchereria bancrofti and Wuchereria malayi (filarial worms).

→ They normally cause inflammation of the organs in which they live for many years.

→ They normally affect the lymph vessels of the lower limbs (causing them to swell like that of an elephant, hence called elephantiasis).

→ Genital organs may also be affected leading to gross deformities.

→ Female Culex mosquito is the vector.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

7. Prevention and Control of Infectious Diseases
The following practices can prevent/control most of the infectious diseases.

  • Maintenance of personal hygiene (keeping the body clean, consumption of clean food and water).
  • Maintenance of public hygiene (proper disposal of excreta/wastes, periodic cleaning and disinfection of water reservoirs; observing standard practices of hygiene in public catering).
  • Eradication of vectors and their breeding places.
  • Vaccination and immunisation for diseases like polio, diphtheria, tetanus, etc.
  • Use of antibiotics and drugs to treat the infected persons.


Immunity could be defined as resistance to disease.

Body defence is broadly classified into two types –

  1. Non-specific or innate body defence
  2. Specific or acquired body defence

Non-Specific Body Defences: (Innate Immunity):
Non-specific body defences are those that are present by birth in a healthy individual to protect from from wide range of harmful microorganisms in the environment, but not-specific against any particular pathogen.
Then non-specific defence mechanisms are of two types.

  1. Surface barriers
  2. Cellular and Biochemical defences

Surface Barriers (Physical Barriers):
They form the first line of defence. It includes skin and mucus membrane.

It is the outermost body surface covering which forms a barrier, that prevents the entry of pathogens and other harmful substances into the body. Certain regions in the skin become heavily keratinized forming an impermeable physical barrier. Keratin is a sclero protein and resistant to weak acids, bases, bacterial enzyme and toxins. Sweat (sudorific gland) secreted by skin makes the surface acidic. This inhibits the growth of bacteria. Sebum (Oily secretion of sebaceous glands) contains chemicals that are toxic to bacteria.

Mucus membrane:
They are the membranes found, lining the various entry points of the body like, eyes, respiratory paths, genital openings, anus etc. The mucus (fluids) produced by these linings trap the micro-organisms and immobilizes them. Skin and mucus membranes also produce a variety of chemicals which serve the following functions.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Protective functions:

  • Saliva produced in the oral cavity contains lysozyme that destroys bacteria.
  • Vaginal secretions of adult females are acidic inhibiting the growth of bacteria and fungi in the female reproductive tract.
  • The mucosa of stomach secretes hydrochloric acid and protein digesting enzymes that destroys pathogens in stomach.
  • Lacrimal fluid (tear) which washes and lubricates the eyes continuous also contains bactericidal lysozyme.
  • Mucus produced in the respiratory tract, traps micro-organisms that try to enter the lungs.
  • Urine normally with acidic PH of 6-5 inhibits bacterial growth.
  • Earwax secreted by ceruminous glands in the ear canal, traps the dust, microorganisms and insects that enter into the ear.
  • Human milk rich in antibacterial substances namely lactoferritin and Neuraminic acid.

Cellular and Bio-chemical defences:

They are the internal defence barriers present in the body and form the second line of defence. They Include.

  1. Phagocytosis,
  2. Natural killer cells (NK Cells),
  3. Interferons and
  4. Inflammatory response.

1. Phagocytosis:
It is a process in which the phagocytic leucocytes (WBC) engulf the pathogen (disease causing agent) and digest it with the help of lytic enzymes. The cells involved in phagocytosis are called phagocytes. The chief phagocytes are macrophages which are derived from a type of WBC called Monocytes and Neutrophils.

A phagocyte engulfs the particulate matter through the formation of pseudopodia. The vesicle thus formed inside the phagocyte is called phagosome. The phagosome then fuses with the lysosome containing hydrolytic enzymes to form phagolysosome. Inside the phagolysosome, the particulate matter is broken down.

2. Natural Killer Cells (NK Cells):
Natural Killer Cells are non-phagocytic larger lymphocytes which have large granules. These cells show natural cytotoxicity and are able to kill a range of tumor cells. NK Cells are not phagocytic but promote cell lysis by direct attack on target cell membrane and releasing of several cytolytics like cytolysin and perforin.

3. Interferons:
These are the anti-microbial proteins released by virus infected cells that protect other healthy tissue cells from infection. During viral infection, nucleic acid enters the host cell. This triggers the genes in most of the cells to produce interferons. The host cell dies due to viruses, but interferons diffuse into other healthy cells and block the synthesis of viral proteins. When a new virus enters the cells it can’t multiply as the cell can’t produce the proteins. The virus needs to reproduce in order to spread infection.

4. Inflammatory response:
It is a biochemical local defensive response of the non-specific defence mechanism to infection and tissue damage (Such as cuts, insect bites, etc.) It is expressed in the form of swelling, pain, and irritation. It is also brought about by phagocytes.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Advantages of Inflammatory response:

  • It prevents spreading of harmful agents to adjacent tissues.
  • It helps in disposal of pathogens and dead cells.
  • It promotes tissue repair process.

Specific Body Defences: (Acquired or Adaptive Immunity)

Specific body defences are those effective defence mechanisms that are acquired by a healthy individual to protect themself from potentially harmful microorganisms in the environment. As it is effective against a specific pathogen, it is referred to as specific immunity.

Antigen is defined as “A foreign substance which when introduced into a living body, is capable’of generating an immune response by stimulating the production of antibodies.

An antigen has two important properties:

  1. Antigenicity: It is the ability to generate a specific immune response to produce antibodies.
  2. Immunogenicity: It is the ability to react specifically with the antibodies produced.

Antibodies are the protective chemicals produced by the body in response to the presence of foreign substances called antigens. Antibodies were named as immunoglobulins by Harman in 1959. The chemical structure of antibodies was discovered by Gerald Edlemen.

Types of Antibodies:
There are five major classes of antibodies, based on the constant regions in their H-chain. They are designated at IgM, IgA, IgD, IgG and IgE. They all have the same basic Y-shaped structure. IgA occurs in both monomer and diemer forms. IgM is a pentamer consisting of five monomers. Others occur only as monomers.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Structure of an antibody molecule:

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1. It is a Y-shaped protein molecule whose surface has a shapecomplementary to the determinant group of the antigen.

2. Each antibody molecule is made up of 4 polypeptide chains.

3. Out of four polypeptide chains, 2 of them are identical short stands called light chains with low molecular weight and other two are identical long strands called heavy chains. with high molecular weight. Long chain contains around 400 amino acids whereas the short chain Structure of an antibody molecule contains 200 amino acids.

4. These four chains are held together by disulphide bonds forming a Y-shaped molecule.

5. Each chain has a constant region (C) and a variable region (V).

6. The variable regions are present at the tip of each arm of Y-molecule. They form an antigen binding site. The rest of the arm forms the constant region.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Differences between antigen and antibody:

Antigen  Antibody
1. They are foreign substances capable of generating an immune response and stimulate the production of antibodies. 1. They are protective chemicals which are produced in response to the presence of foreign substances called antigens.
2 Generally it is protein, but it may also be a polypeptide, complex lipid and certain other substances that combine with proteins. 2 It is a protein molecule.
3. They are present on the surface of micro – organisms or as free molecules. 3. They are present on the surface of plasma cells and in body fluids.
4. They bind a macrophage to reach a helper T-cell to initiate an immune response. 4. They react with antigen directly to destroy them.

Role of B-lymphocytes and T-lymphocytes in immune system:
B-lymphocytes and T-lymphocytes play an important role in humoral immunity and cell-mediated immunity respectively.

Role of B-lymphocytes in humoral immunity:
B-lymphocytes undergo maturation and become immunity competent in the bone marrow.
The B-lymphocytes are responsible humoral immunity. In this type of immunity, the body fights against the pathogen by producing antibodies, in the fluids like plasma, lymph, etc.

→ When an antigen enters the body, it is recognized by the B-cells which get activated with the help of the hdlper T – cells, which secrete specific substances called lymphokines for the activation. The cell surface membrane of B-cells is capable fonning only one type of antibody.

→ Once the B-cell is activated, it is bound to the specific antigen and responds by producing 2 types of cells namely plasma cells and memory cells.

→ The plasma cells secrete large quantities of anti-bodies into the general emulation (Blood and lymph) specific for antigen.

→ These antibodies combine with the antigens and destroy them.

→ The memory cells survive for long periods and persisting in the body, ready to mounta secondary response against the pathogen, if re-infection occurs.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Role of T-lymphocytes that migrate from bone marrow to thymus: T-cells are responsible for the cell mediated immunity. In this type of immunity, antibodies are not formed, but the body produces a large number of activated T-cells that are specially designed to destroy the foreign organisms.

1. When an antigen enters the body, T-cells get activated and individually respond to the antigen by producing their elopes called lymphoblasts and memory cells.

2. These clones of T-cells are similar, but perform different functions.

3. They do not produce antibodies, but develop further to produce one of the following. 3 types of T-cells, namely.
(a) T-killer cells : They destroy the antigen before it can spread an infection by secreting certain substances like cytolysin.
(b) T-helper cells : They activate B-cells (to produce antibodies) and T-killer cells (To kill the antigens by secreting certain substances called lymphokines).
(c) T-suppressor cells : These inhibit the immune response of both T and B lymphocytes to foreign antigens when infection is controlled.

4. The memory cells persist in the body and readily mount a secondary response against the pathogen if reinfection occurs.

Differences between B-lymphocytes and T-lymphocytes

B-lymphocytes  T-lymphocytes
1. They are responsible for humoral immunity. 1. They are responsible for cell mediated immunity.
2. They provide protection against certain viruses and bacteria which enter the blood and lymph. 2. They provide protection against certain viruses, bacteria, protozoan’s, fungi which enter the cells.
3. They divide and form a clone of B-cells (plasma cells) and memory cells. 3. They divide and form a clone of T-cells (lymphoblasts) and memory cells.
4. They do not move to the region of infection but produce antibodies that pass into the blood and lymph which destroy the antigens. 4. The killer cells move to the region of infection and secrete cytolysin.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Antigen Presenting Cells:

These are specialised group of cells like macrophages (Monocytes of blood and histocytes of tissues). They posses MHC (Major Histocompatability complex) on their surface and with this complex, they bind to the antigen, process it and present it to the lymphocytes. The T – helper cells specifically interact with the presented antigen and become activated. It is the function of antigen presenting cells to activate the immune system.

Types of immunity: Immunity is of two types.

  1. Active immunity
  2. Passive immunity

1. Active immunity:
→ Immunity provided by antibodies produced by B-cells in their encounter with antigens is called active immunity. It may be natural or artificial.

→ Naturally acquired active immunity results from any bacterial or viral infection. During infection, antibodies are produced against the pathogen. If the individual contacts with the same pathogen again, the disease will not affect the person as the antibodies are already present in the body.

→ Artificially active immunity is introduced into the body through a process called vaccination or immunization. In this process, dead or attenuated (living but extremely weakened) pathogens are introduced into the body in the form of vaccine. This induces immune response and antibodies are produced in the body.

2. Passive immunity:
→ Immunity provided to an individual by the introduction of borrowed antibodies obtained from an immunized animal is called passive immunity. Passive immunity may be natural or artificial.

→ Naturally acquired passive immunity results through the natural transfer of antibodies. The transfer of antibodies from mother’s body into the foetus through placenta is a typical natural passive immunity. The baby is protected for several months after the birth.

→ Artificially acquired passive immunity results by transfer of antibodies produced in the body of one individual into other through injections. The donated antibodies provide protection for short period. The serum containing antibodies (globulins) is used for treating snake bites, rabies and tetanus etc.

2nd PUC Biology Notes Chapter 8 Human Health and Disease


→ Allergy can be defined as the exaggerated or hypersensitive reaction of the immune system to certain antigens present in the environment.

→ The substance/agent which causes the hypersensitive reaction of the immune system, is called an allergen, e.g., dust mites, pollen grains, animal dandruff, etc.

→ The antibodies produced in response to allergens are of IgE type.

→ The common symptoms of allergy are :

  • sneezing
  • watery eyes,
  • rashes,
  • running nose and
  • difficulty in breathing (asthma).

→ These symptoms are produced due to release of histamine and serotonin from the mast cells.

→ Drugs like antihistamine, adrenaline and steroids quickly reduce the symptoms of allergy.

→ Reasons for Allergy: Allergies tend to run in families, suggesting that they have a genetic basis. It has been found that breast fed infants are less prone to certain allergies later in life, than bottle fed ones.

→ Diagnosis: For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens, and the reaction is studied. The use of drugs such as antihistamine, adrenaline and steroids quickly reduce the symptoms of allergy.

→ Autoimmunity: Autoimmune diseases are those disorders caused when the body’s immune system goes off the track and starts destroying self cells and molecules by treating them as foreign particles,
e g., Rheumatoid arthritis and multiple sclerosis.

Immune System :
→ The main function of an immune system is to recognise the foreign molecules (antigens), respond to them and keep a memory of them.

→ It also plays a role in:

  • organ transplantation,
  • allergic reactions and
  • autoimmune diseases.

→ Immune system consists of lymphoid organs, tissues, cells and molecules like antibodies.

→ Lymphoid organs are the organs where the origin, and or maturation and proliferation of lymphocytes take place.

→ Lymphoid organs can be classified into two groups:
(a) Primary lymphoid organs and
(b) Secondary lymphoid organs.

(a) Primary lymphoid organs are those where the immature lymphocytes undergo maturation/ differentiation into antigen-Specific lymphocytes, e.g., Bone marrow and thymus.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

(i) Bone Marrow:

  • It is the main lymphoid organ where all types of blood cells including lymphocytes are formed.
  • Bone marrow provides the microenvironment for the development and maturation of B- lymphocytes.

(ii) Thymus:

  • Thymus is located beneath the chest bone near the heart.
  • This gland keeps reducing in size with age.
  • It provides the microenvironment for the development and maturation of T-lymphocytes.

(b) Secondary lymphoid organs are those, where the lymphocytes interact with, the antigen and proliferate to form a clone (effector cells and memory cells), e.g., spleen, lymph nodes, tonsils, appendix and peyers patches of small intestine.

(i) Spleen:

  • It mainly contains lymphocytes and phagocytes.
  • It acts as a filter of the blood by trapping blood-borne microbes.
  • It is also a reservoir of erythrocytes.

(ii) Lymph nodes:

  • Lymph nodes are small solid structures, found at different points along the lymphatic , system.
  • They act as filters and trap the microbes that have entered the lymph.
  • Antigens trapped in them activate the lymphocytes present in the lymph nodes and produce ah immune response.

(iii) Mucosal-associated lymphoid tissues (MALT):
→ Lymphoid tissue located within the mucosal lining of the major tracts (respiratory, digestive, urinogenital tracts), is called mucosal-associated lymphoid tissue.

→ It accounts for about 50% of the lymphoid tissue in a human body.

Acquired Immuno Deficiency Syndrome (AIDS):

→ Acquired Immuno Deficiency Syndrome is popularly known as AIDS. AIDS was first observed in an homosexual male in USA during 1981. AIDS is a viral disease caused by HIV (Human Immunodeficiency Virus). Earlier this virus was also called HTLV or LAV. HTV is of two strains namely HIV – 1 and HTV – 2. HTV-1 is almost cosmopolitan, whereas HIV-2 is at present restricted to Western Africa.

→ HIV has a protein coat and a RNA core. When HTV infects a person, it may not result in AIDS though the person is HTV +ve. HIV undergoes an incubation period. During incubation period HIV releases its RNA into helper T-Lymphoeytes. This viral RNA conducts reverse transcription and multiplies in number by destroying helper T-Lymphocytes. Hence, earlier stage of infection can be detected by counting helper T-Lymphocytes in blood (normal count is 1200/mm3, any deviation from this is HIV +ve).

→ Gradually as a major symptom, breakdown of the defence system in the°body of the patient can be noticed. Hence the name acquired immuno deficiency syndrome. As subsidiary symptoms, loss of body weight, repeated infections, dry cough may also appear. ELISA (Enzyme Linked Immuno Sorbant Assay) and western Blot test are tests for detecting HIV.

→ At present there is no cure for AIDS. Hence prevention is better than cure. Preventive measures include,

  • Clean sexual habits.
  • Screening of blood and blood products before use.
  • Screening of organs and tissues before transplantation.
  • Weaning of drug addicts.
  • Use of sterilized instruments in hospitals and barber shops.
  • Popularising disposable syringes, etc.,

2nd PUC Biology Notes Chapter 8 Human Health and Disease

→ However at present AIDS patients are treated with two drugs. Namely,

1. AZT (Azido Thimidine or Zidio Vudine) – It temporarily prevents reverse transcription of viral RNA.

2. ddl (Dideoxyinosine) – It temporarily prevents replication of HIV.
These drugs are not 100% safe and permanent cure for AIDS. However they can prolong the span of life by a small extent.
Recently, Biotechnologists are working on HTV in combination with virus causing canarypox to develop vaccine against AIDS.

(b) Life Cycle of HIV.

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→ The virus after getting into the body of a person, enters the macrophages.

→ The RNA replicates and DNA is formed by reverse transcriptase.

→ The viral DNA gets incorporated with the host cell DNA and directs the infected cell to produce virus particles.

→ The macrophages continuous to produce virus particles.

→ The virus then enters the helper T-Iymphocytes (T4), replicates and forms progeny viruses.

→ The progeny viruses released in the blood, attack other helper T-lymhocytes and there is a . progressive decrease in the number of helper T-Iymphocytes in the body of the infected person.

→ The person becomes easily infected by bacteria like Mycobacterium, viruses and even parasites like Toxoplasma.

→ The person is unable to project himself/herself against any infection.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

(c) Prevention of AIDS:
→ National AIDS control Organisation (NACO) and non-governmental organisations are trying their best to educate people about AIDS.

→ World Health Organisation (WHO) has started a number of programmes to prevent spreading , of HIV infection; some such steps include :

  • ensuring use of disposable needles and syringes.
  • checking blood samples for HIV.
  • free distribution of condoms and advocating safe sex.
  • controlling drug abuse.
  • promoting regular check-up for HIV in susceptible populations, etc.

→ AIDS is diagnosed byELISA (Enzyme-linked lmmuno sorbant Assay) test.

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


Cancer may defined as the abnormal uncontrolled growth of certain tissue cells.

Types of tumours or cancers:
Tumour can be classified into two types:
1. Benign tumours: Tumours result from abnormal and persistent cell division consists of cancer cells that remains localized at the spot of origin and do not spread to distinct sites. These are not great threat to life (non – fatal), but some can be fatal, as in brain tumour. Well differentiated cells generally characterize benign tumours.

2. Malignant tumours: Tumours result from abnormal and persistent cell division consist of cancer cells that may be carried by the circulating fluid (blood or lymph) or by direct penetration to other part of the body and changing the neighbouring tissues where they induce secondary* tumours. Malignant tumours usually contain undifferentiated cells. These are fatal to the organism. The phenomenon of formation of secondary tumours is called metastasis.

Classification of cancers:
Cancers are grouped into the following 4 main types.

1. Carcinoma: Any cancer that arises in the epithelial tissue, is called a carcinoma. Examples, brain tumour, lung cancer, skin cancer, breast cancer, etc.

2. Sarcoma: Any cancer that arises in the connective tissue of the body is called a sarcoma These tumours can arise at any part of the body such as fibrous muscles, cartilage, bone, blood and lymph vessels etc. Example are multiple myeloma, osteoqenic sarcoma (bone cancer), muscle cancer etc.

3. Lymphoma: Any cancer that arises in the lymph nodes or lymph glands is called lymphoma. It is characterized by painless enlargement of lymph glands, e.g. Hodgkin’s lymphoma and non – Hodgkin’s lymphoma.

4. Leukemia: This is commonly called the blood cancer. In this type, the bone marrow and the other blood producing cancerous immature white blood cells in more than numbers required. This condition is called leukemia or blood cancer.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Characteristics of cancer cells:
→ Anaplastic or undifferentiated cells: The cancer cells lack normal cell cycle where the daughter cells.

→ Immortality: These cells do not age normally and continue dividing indefinitely.

→ Change in the structure of cell: There is disorganization of the cytoskeleton which alters the shape of the cell. Mitochondria swell and lack cristae. Cancer cells also show large, irregularly shaped nuclei and prominent nucleoli. There is an increase in the number of rough ER and ribosomes and further, permeability of plasma membrane also gets altered.

→ Invasiveness: Cancer cells grow by progressive infiltration, penetration and destruction of the surrounding tissues.

Causes of cancer (Carcinogenic agents):
These include physical, chemical and biological agents, which transform normal cells by directly causing changes in the DNA of this cells.
1. Physical agents: They include various forms of ionizing radiations. UV radiation is a powerful mutagen for skin cancer. The exposure of the thyroid glands to x – rays has shown to increase the incidence of thyroid cancer.

2. Chemical agents: The chemical carcinogens that have been found to be carcinogenic in humans include:.
a. Chemical mixtures like soot (black carbon), tars, cigerette Smoke, etc.,
b. Industrial chemicals: Arsenic, nickel coumpound, benzidine, etc.,
c. Drugs: Mustard gas, phenacetin.

(a) Prevention and treatment of cancer:
There are two methods of cancer prevention, i.e., primary and secondary preventions. Primary method is concerned with protecting people from the causative agents and secondary prevention is aimed at correction of pathological states, which is already present.
The treatment of cancer depends on its type and severity and on the organ that is diseased. Ill early stages, cancer is curable by radiotherapy or chemotherapy.

Drug Abuse:

Narcotic drugs:
Drugs that dull the senses, induce sleep and cause Euphoria (feeling well being) are called narcotic drugs. The prolonged use of narcotic drugs, leads to the dependence of the body, on these drugs. This is referred to as drug addiction.

Classification of narcotic drugs :
Narcotic drugs are classified into four types, based on their effect on the body. They are
(a) Stimulants or Coca alkaloids : These are narcotic drugs which tend to stimulate CNS, make a person more alert, wakeful and provide excitement. They are also called superman drugs as the person is able to be awake for long periods and is capable of doing more work than others. Chronic (long time) use of cocaine (from coca plant) can cause severe physical, changes in brain, damage to tissues of the nose, lungs, heart and respiratory failure, e.g.; Caffeine, cocaine, Tobacco (nicotine).

(b) Depressants or sedatives or tranquilisers : These are narcotic drugs that depress the activity of CNS (central nervous system). They also create a feeling of calmness, relaxation, drowsiness and deep sleep under high dosage.
e.g. : Alcohol is the most common legal depressan. Other depressants are Barbiturates, Benzodiazepine (Valium).

(c) Analgesics or opiods : These are narcotic drugs that reduce or relieve pain and also suppress brain activity. Some synthetic opiates are also used as ingredients in medicines for cough and diarrhea.
e.g.: Codium, morphine, heroin (brown sugar), pethidine, methadone.

(d) Hallucinogens or cannabinoids : These are narcotic drugs which are generally called mind expanding drugs. They cause sensory perceptions that have ho external stimuli. A person may see, hear, smell or feel things that do not exist. Regular use of hallucinogens can cause dis co-ordination, increased heart beat rate, depression, decreased levels of sex hormones and poor judgement.
e.g.: LSD (Lysergic acid diethylamide), marijuana, charas, ganja, etc.
The drugs that are commonly abused, include opioids, cannabinoids and coca-alkaloids. Other drugs like barbiturates, amphetamines, benzodiazepines and lysergic aqid diethylamide (LSD) are also abused.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Effects of alcohol on body parts:

→ Alcohol addiction or alcoholism: Regular consumption of alcohol leads to dependency on alcohol, which is known as alcoholism or alcohol addiction. Alcohol addiction in modem days is mainly due to many social, psychological and physical problems.

→ Effect of alcohol on the nervous system: Alcohol has direct effect on brain and leads to dis co-ordination of movement, dementia, and partial loss of memory (amnesia). During this period, the person is unable to remember anything. There is a loss of moral sense and indulgence in antisocial behaviour and loss of body balance.

→ Effect on the stomach: Alcohol stimulates excessive secretion of gastric juice which may lead to inflammation of gastric mucosa and also leads to hyperacidity and ulcer.

→ It also affects food intake and digestion. It may lead to loss of appetite (hunger), indigestion, vomiting and diarrhea.

→ Effect on the liver: Excessive consumption of alcohol affects the normal functioning of liver. It includes fibrosis (Formation of fibrous tissue on liver) and cirrhosis (degeneration of liver tissue). It can also lead to jaundice.

Effect on the kidney:
It affects the normal functioning of kidney and leads to kidney failure.

Effect on the foetus:
Consumption of alcohol during pregnancy, affects the normal growth and development of foetus and leads to congenital defects such as heart diseases, abnormal limb development, etc.

In addition to all these bodily effects, it also affects the social life i.e. family in particular and society in general.

2nd PUC Biology Notes Chapter 8 Human Health and Disease

Efforts to encounter drug menace:

  • A gradual decrease in the intake of drugs.
  • Substitution of drugs which are less harmful.
  • Psychiatric counselling.
  • Medical treatment is required to supervise withdrawal of drugs.
  • If the deaddiction is to be successful, the addicted person needs total support from his family.

Community should be educated through mass media like radio, TV, films, News paper, etc about the hazards of drug addiction and effect of these drugs on a persons body, family and society.

Enactment of law:
The possession of drugs, selling and using of drugs is an offense. Hence Government, of all countries should punish the criminals and discourage the selling of drugs and alcohol in public. Society should accept ex-drug addicted persons and treat them kindly. It is because basically, society is responsible to produce drug addicts.

2nd PUC Biology Notes

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