CBSE Class 12 Biology Human Health And Disease Worksheet

Question. Which one is not a symptom of disease caused by E. histolytica ?
(a) Stools with excess mucus and blood clots
(b) Constipation smacked
(c) Abdominal pain and cramps
(d) Nasal discharge 
Answer : D

Question. Infection of Ascaris usually occurs by 
(a) drinking water containing egg of Ascaris
(b) eating imperfectly cooked pork
(c) tse-tse fly
(d) mosquito bite 
Answer : A

Question. The group of diseases carried (transmitted) by insects are
(a) typhoid, jaundice, tuberculosis
(b) mumps, measles, smallpox
(c) scabies, ringworm, swine flu
(d) malaria, filaria, yellow fever 
Answer : D

Question. Which of the following disease is caused by a protozoan?
(a) Syphilis
(b) Influenza
(c) Babesiosis
(d) Blastomycosis
Answer : C

Question. Fungi belonging to genera–Microsporum, Trichophyton and Epidermophyton are responsible for
(a) ringworm infection
(b) skin allergy
(c) amoebiasis
(d) measles
Answer : A

Question. Which one of the following diseases is spread by housefly?
(a) Dengue fever
(b) Encephalitis
(c) Filariasis
(d) Amoebiasis
Answer : D

Question. Gambusia is a fish which can control the mosquito borne disease like
(a) dengue
(b) malaria
(c) chikungunya
(d) All of these
Answer : D

Question. Rhinovirus causes
(a) common cold
(b) malaria
(c) AIDS
(d) pneumonia
Answer : A

Question. Common cold differs from pneumonia in, that
(a) pneumonia is a communicable disease, whereas the common cold is a nutritional deficiency disease
(b) pneumonia can be prevented by a live attenuated bacterial vaccine, whereas the common cold has no effective vaccine
(c) pneumonia is caused by a virus, while the common cold is caused by the bacterium Haemophilus influenzae 
(d) pneumonia pathogen infects alveoli whereas the common cold affects nose and respiratory passage but not the lungs
Answer : D

Question. Ringworm is a/an
(a) air borne disease
(b) infectious disease
(c) non-infectious disease
(d) None of these
Answer : B

Question. Give the name of two helminths, which cause ascariasis and filariasis, respectively.
(a) Ascaris and Wuchereria
(b) Wuchereria and Ascaris
(c) Roundworm and flatworm
(d) Plasmodium and Wuchereria
Answer : A

Question. The filariasis pathogen is transmitted to a healthy person through the bite of
(a) female Anopheles mosquito
(b) female Aedes mosquito
(c) female Culex mosquito
(d) None of the above
Answer : C

Question. Fill up the blanks.
I. Heat and moisture help ............ fungi to grow, which makes them thrive in skin folds.
II. Maintenance of ............ and ............ hygiene is important for the prevention of manyinfectious diseases.
III. ............ gives the diseases its name, elephantiasis. 
(a) I. Microsporum, II. public; personal, III. Swelling of hand
(b) I. Trichophyton, II. personal; public, III. Enlargement of eye
(c) I. Epidermophyton, II. personal; public, III. Swelling of legs
(d) I. Wuchereria, II. personal; public; III. Enlargement of tongue
Answer : C

Question. Adults of Wuchereria bancrofti attack 
(a) excretory system
(b) digestive system
(c) lymphatic system
(d) nervous system
Answer : C

Question. Infective stage of Plasmodium for man is
(a) merozoites
(b) ookinetes
(c) sporozoites
(d) None of these
Answer : C

Question. Elephantiasis, a chronic inflammation that results in gross deformities is caused by
(a) Trichophyton
(b) Wuchereria
(c) E. coli
(d) Ascaris
Answer : B

Question. Which of the following toxic substances is responsible for the high malarial fever?
(a) Haemoglobin
(b) Haemocyanin
(c) Haemozoin
(d) Haemoriden
Answer : C

Question. Pneumonia is an infection of the ......A...... . The most common cause of pneumonia is a type of bacteria known as .....B.... and .....C....... .
Most suitable combination to fill the blanks is
(a) A–liver, B– Salmonella typhi, C–Streptococcus pneumoniae
(b) A–lungs, B–Streptococcus pneumoniae, C–Haemophilus influenzae
(c) A–blood, B–Streptococcus pneumoniae, C–Haemophilus influenzae
(d) A–heart, B–Salmonella typhi, C–Haemophilus influenzae
Answer : B

Question. Elephantiasis causing organism belongs to
(a) Aschelminthes
(b) Platyhelminthes
(c) Cnidaria
(d) Porifera
Answer : C

Question. Measures for personal hygiene include.
(a) Intake of clean drinking water
(b) Keeping the body clean
(c) Disinfection of water resources
(d) Both (a) and (b)
Answer : D

Question. Which of the following endoparasites of humans does show viviparity? 
(a) Ancylostoma duodenale
(b) Enterobius vermicularis
(c) Trichinella spiralis
(d) Ascaris lumbricoides
Answer : C

Question. Which of the following diseases causes internal bleeding, muscular pain, fever, anaemia and blockage of the intestinal passage?
(a) Ascariasis
(b) Filariasis
(c) Amoebiasis
(d) Trypanosomiasis
Answer : A

Question. A disease which can easily transmit from one person to another is called
(a) non-infectious disease
(b) infectious disease
(c) viral disease
(d) bacterial disease
Answer : B

Question. Which of the following health disorder includes symptoms of fever, chills, cough, headache, grey to bluish lips and fingers nails?
(a) Filariasis
(b) Typhoid
(c) Pneumonia
(d) Malaria
Answer : C

Question. In which disease does mosquito transmitted pathogen cause chronic inflammation of lymphatic vessels?
(a) Ringworm disease
(b) Ascariasis
(c) Elephantiasis
(d) Amoebiasis
Answer : C

Case-based MCQs

Attempt any four sub-parts from each question.

Each sub-part carries 1 mark.

I. Read the following text and answer the following questions on the basis of the same :
Shivani studies in class I. Her parents come from a backward family and are unaware of immunization programme. So, she did not get vaccinated properly. Once playing with her friends in the park, she fell down due to weakness and later complained of high fever, headache and stiffness in her neck.

Question. The disease that Shivani has contracted spreads through :
(A) Mosquito bite
(B) Bite of infected dog
(C) Faecal oral route
(D) Direct contact of an infected person
Answer : C

Question. The microbe responsible for Shivani’s illness may be :
(A) Vibrio cholerae
(B) Enterovirus
(C) Plasmodium
(D) Mycobacterium
Answer : A

Question. This type of infection produces inflammation in :
(A) Bones
(B) Liver
(C) Nervous System
(D) Heart
Answer : C

Question. Which vaccine if administered earlier, would have saved Shivani from the illness she contracted unfortunately?
(A) MMR Vaccine
(B) Varicella Vaccine
(C) BCG Vaccine
(D) Salk Vaccine
Answer : D

Question. A step that can help to eradicate the disease Shivani has contracted is :
(A) Live polio vaccine
(B) Killed polio vaccine
(C) Combination of live and killed vaccines
(D) None of the above
Answer : C

II. Read the passage and answer any four questions.
A group of youth were having a ‘rave party‘ in an isolated area and was raided by police. Packets of ‘smack‘ and syringes with needles were found littered around. Syringes and needles are used to inject drugs intravenously, as this can have very quick and strong effect upon abuser. Higher chances of addition can be seen through this mode of administration of drugs. Infected syringes may cause the user to catch deadly diseases.

Question. ‘Smack’ is a drug obtained from the
(A) Latex of Papaver somniferum
(B) Leaves of Cannabis sativa
(C) Flowers of Datura
(D) Fruits of Erythroxylum coca
Answer : A

Question. Why is taking ‘smack‘ considered an abuse ?
(A) because it causes drug dependence
(B) because it affects nervous system
(C) because it impairs one’s psychological functions
(D) all of these
Answer : D

Question. Syringes and needles used by the youth for taking the drug could prove to be very fatal as :
(A) They can acquire serious infections.
(B) They can lead to malnutrition.
(C) They can cause transmission of parasitic disease.
(D) They can lead to cardiac arrest.
Answer : A

Question. Which of the following drug is commonly known as Smack?
(A) Heroin
(B) Morphine
(C) Codeine
(D) Pethidine
Answer : A

Question. Infected syringes disposes the user to catch which of the following disease :
(A) HIV/AIDS
(B) Hepatitis-B
(C) Hepatitis-C
(D) All of the above.
Answer : D

Very Short Answer Type Questions

Question. Why is it that during changing weather, one is advised to avoid closed, crowded and air conditioned places like cinema halls etc?
Answer : During changing weather one is advised to avoid crowded places, because changing seasons are the time when infectious agents are more prevalent as moist condition favoures pathogen to grow fast and people are more vulnerable as their body system is busy in adapting the changing environmental conditions of temperature humidity, etc and they get infected to there pathogen easily.

Question.  The harmful allele of sickle-cell anaemia has not been eliminated from human population. Such afflicted people derive some other benefit. Discuss.
Answer : Sickle-cell anaemia still persists in the population despite being harmful because this mutation can also be beneficial in certain conditions. The mutant Hb5 type haemoglobin is found at high frequencies (up to 20% and above) in the tropical Africa. It is known that heterozygotes (Hbs /HbA), having both types of haemoglobin show resistance to malarial infection because the body targets the Plasmodium falciparum infected cell for destruction. In contrast, individuals homozygous for normal haemoglobin (HbA/HbA) suffer high mortality rates in early childhood due to malarial infection. Thus, the allele for sickle cells has been maintained because heterozygotes have a higher reproductive success than either of the two possible homozygotes.

Question. Certain pathogens are tissue/organ specific. Justify the statement with suitable example.
Answer : Certain pathogens are tissue/organ specific as they are adapted to overcome the resistance mechanisms of those tissues and organs, e.g., the pathogens that enter the gut must know a way of surviving in the stomach at low pH and resistant to various digestive enzymes.

Question. The immune system of a person is suppressed. In the ELISA test, was found positive to a pathogen.
(a) Name the diseases the patient is suffering from.
(b) What is the causative organisms?
(c) Which cells of body are affected by the pathogen?
Answer : The immune system of a person is suppressed. In the ELISA test, he was found positive to a pathogen.
(a) The patient is suffering from AIDS.
(b) AIDS is caused by Human Immuno deficiency Virus (HIV). It is a retro virus containing RNA as genetic material.
(c) Macrophages and helper T-cells are affected by the pathogen.

Question. Why is Gambusia introduced into drains and ponds?
Answer : To feed on mosquito larvae so as to eliminate the vectors responsible for causing malaria.

Question. How does haemozoin affect the human body when released in blood during malarial infection?
Answer : Haemozoin is responsible for the chill and high fever recurring every three to four days during malarial infection

Question. State two different roles of spleen in the human body.
Answer : Spleen is the secondary lymphoid organ that stores lymphocytes, it filters microbes and acts as a reservoir to store erythrocytes.

Question. Name any two physiological barriers that provide innate immunity? 
Answer : Acid in stomach/saliva in mouth/tears in eyes.

Question. What is it that prevents a child to suffer from a disease he/she is vaccinated against? Give one reason. 
Answer : The immunological memory induced by the vaccine in a child prevents the recurrence of a disease.

Question. How does colostrum provide initial protection against diseases to new born infants? Give one reason.
Answer : Colostrum contains several antibodies which are absolutely essential for developing resistance in the new-born babies.

Short Answer Type Questions

Question. Diseases like dysentery, cholera, typhoid, etc., are more common in over crowded human settlements. Why?
Answer : Dysentery, cholera and typhoid are more common in crowded settlements because these are infectious diseases and spread from person to person contact. Water gets contaminated with the excreta of infected people and causes the spread of infection to other people.

Question. From which plant cannabiniods are obtained? Name any two cannabinoids. Which part of the body is effected by consuming these substances?
Answer : Cannabinoids are obtained from the inflorescence of the plant Cannabis sativa. Marijuana, hashish, charas, ganja are some cannabinoids. These chemicals interact with cannabinoid receptors of the body, mainly present in the brain. Cardiovascular system of the body is effected adversly by consuming these substances.

Question. In the metropolitan cities of India, many children are suffering from allergy/asthma. What are the main causes of this problem. Give some symptoms of allergic reactions.
Answer : In metropolitan cities life style is responsible in lowering of immunity and sensitivity to allergens. More polluted environment like dust in surroundings increases the chances of allergy in children. Some symptoms of allergic reactions are sneezing, watery eyes, running nose and difficulty in breathing

Question. What is the basic principle of vaccination? How do vaccines prevent microbial infections? Name the organism from which hepatitis-B vaccine is produced.
Answer : The principle of vaccination is based on the property of ‘memory’ of immune system. In vaccination, a preparation of antigenic proteins or inactivated/live but weakened pathogens is introduced into the body. The antigens generate primary immune response by producing antibodies along with memory B-cells and T-cells. When the vaccinated person is attacked by the same pathogens, the existing memory B-cells and T-cells recognise the antigen and overwhelm the invaders with massive production of lymphocytes and antibodies. Hepatitis-B vaccine is produced from yeast.

Question. What is cancer? How is a cancer cell different from the normal cell? How do normal cells attain cancerous nature?
Answer : An abnormal and uncontrolled division of cells is termed as cancer. Genes called cellular oncogenes (c-onc) or proto-oncogens present in normal cells when activated under certain conditions lead oncogenic transformation of the normal cells leading cancer. A cancer cell is different from the normal cell in following ways (Image 156)

Question. A person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air. Identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions.
Answer : If a person is hypersensitive to certain substance present in the air, he may be allergic to it. Mast cells release certain chemicals, e.g., histamine and serotonin, in response to this substance, that result in allergic reaction. Precaution taken to prevent such reaction is to avoid the allergens responsible for particular allergy.

Question. For an organ transplant, it is an advantage to have an identical twin. Why?
Answer : For an organ transplant, it is an advantage to have an identical twin because the organ will have same surface markers and therefore, the recipient’s immune system will not identify it as foreign and will not react against it. In case of different surface markers, the immune system starts a reaction, kills the foreign tissue or rejects it.

Question. What are lifestyle diseases? How are they caused? Name any two such diseases.
Answer : Life style disease are caused by specific food habits, work related posture or exposure to harmful radiations or substances, lack of physical exercise, mental stress, etc. e.g., cancer, alcoholism, heart disease, etc.

Question. If there are two pathogenic viruses, one with DNA and other with RNA, which would mutate faster? And why?
Answer : RNA mutates faster than DNA. DNA is more stable and also has better repair mechanisms that correct the changes in base pairs as soon as it is introduced.

Question. Define the term ‘health’. Mention any two ways of maintaining it. 
Answer : Health is a state of complete physical, mental and social well-being.
Good health is maintained by balanced diet/personal hygiene/regular exercise. 

Question. List the symptoms of ascariasis. How does a healthy person acquire this infection?
Answer : Symptoms of ascariasis: Internal bleeding, muscular pain, anaemia, blockage of intestinal passage.
A healthy person can acquire this infection by intake of water, vegetables/fruits/foods contaminated with eggs of the parasite.

Question. Name the causative organism of the disease amoebiasis. List three symptoms of the disease.
Answer : Entamoeba histolytica causes amoebiasis. Symptoms are constipation, abdominal pain/cramps, stool with excess mucous/blood clots.

Question. Write the scientific names of the causal organisms of elephantiasis and ringworm in humans Mention the body parts affected by them. 
Answer : 

Question. Identify a, b, c and d in the following table

Answer : (a) small intestine
(b) Rhino virus
(c) nose and respiratory passage
(d) alveoli of lungs

Question. What is “withdrawal syndrome”? List any two symptoms it is characterised by.
Answer : It is the state experienced by addicts when their regular dose of alcohol/drug is abruptly discontinued. It is often characterised by anxiety, shakiness, nausea and sweating.

Question. How does smoking tobacco in human lead to oxygen deficiency in their body?
Answer : Smoking increases the carbon monoxide (CO) content in the blood which has greater affinity to haemoglobin than oxygen. CO forms a stable bond with haemoglobin and does not allow binding of oxygen. Smoking also damages alveolar walls, which reduces respiratory surface (emphysema).

Question. (a) Name the source plant of heroin drug. How is it obtained from the plant?
(b) Write the effects of heroin on the human body. 
OR
Name an opioid drug and its source plant. How does the drug affect the human body?
Answer : (a) The source drug of heroin is poppy plant (Papaver somniferum).It is derived by acetylation of morphine, which is obtained from the latex of the poppy plant.
(b) Heroin is a depressant and slows down the body functions.

Long Answer Type Questions

Question. What are the methods of cancer detection? Describe the common approaches for treatment of cancer.
Answer : Early detection of cancer is essential. The methods of cancer detection and diagnosis are as follows.
(i) Biopsy and histo-pathological studies of the tissue/ blood/ bone marrow.
(ii) Tests for increased cell counts (in the case of leukaemia blood cancer).
(iii) Techniques like radiography (use of X-rays), CT (computed tomography) and MRI (Magnetic Resonance Imaging) to detect cancers of the internal orgAnswer :
(iv) Detection of cancer specific antigens.
(v) Molecular biology techniques to detect genes in individuals with inherited susceptibility to certain cancers.
The common approaches for treatment of cancer
(i) Surgical removal of tumour.
(ii) Irradiation of tissue to kill cancerous cells.
(iii) Immunotherapy using interferon to boost cancer cell killing.

Question. Drugs like LSD, barbiturates, amphetamines, etc., are used as medicines to help patients with mental illness. However, excessive doses and abusive usage are harmful. Enumerate the major adverse effects of such drugs in humAnswer :
Answer : Harmful effects of drugs like LSD, barbiturates, are
(i) Anxiety, shakiness, nausea and sweating, loss of mind control.
(ii) Reckless behaviour, vandalism and violence.
(iii) Lack of interest in personal hygiene, fluctuations in weight and appetite.
(iv) Withdrawal, isolation, depression, fatigue, aggressive behaviour.
(v) Social adjustment problems
(vi) Withdrawal symptoms can be severe and life threatening.
(vii) Excessive doses of drugs may lead to coma and death may occur due to respiratory failure, heart failure or cerebral haemorrhage.

Question. What is Pulse Polio Programme of Government of India? What is OPV? Why is it that India is yet to eradicate polio?
Answer : Pulse Polio is an immunisation campaign established by the Government of India in 1995-96 to eradicate poliomyelitis (polio) in India by vaccinating all children under the age of five years orally against polio virus. This project deals with the ways to fight poliomyelitis through a large scale immunisation programme, co-operating with various international institutions, state governments and Non-Governmental Organisations. In 1995, following the polio eradication initiative of World Health Organisation (1988), India launched Pulse Polio Immunisation Program along with Universal Immunisation Program which aimed at 100% coverage. Having mate on unprecedented progress in polio eradication, India is now gearing up to be declared polio free by 2014 by guarding itself against the import of polio virus from neighbouring countries and by boosting routine immunisation. Oral Polio Vaccine Oral Polio Vaccine (OPV) is a live-attenuated vaccine, produced by the passage of the virus through non-human cells at a sub-physiological temperature, which produces spontaneous mutations in the viral genome. OPV also proved to be superior in administration, eliminating the need for sterile syringes and making the vaccine more suitable for mass vaccination campaigns. OPV also provides long lasting immunity than the salk vaccine. One dose of OPV produces immunity to all three poliovirus serotypes in approximately 50% of recipients. India is yet to eradicate polio because inspite of many initiatives taken by government, few cases has been reported. The last reported cases of polio in India was in West Bengal and Gujarat on 13 January 2011. Earlier this year, the World Health Organisation (WHO) had removed India from the list of polio-endemic countries. If no fresh case is reported till 2014, the country will be declared polio free. July 30, 2013 a nine-month old boy from Navi Mumbai has been found positive for Vaccine-Derived Polio-Virus(VDPV) type 2 and was on ventilator at BJ Wadia Hospital in Parel. This is the fourth such case recorded in the country that year. In India the main obstacle in the eradication of polio had been the refusal of polio vaccine by certain communities on account of illiteracy and misinformation.

Question. What are recombinant DNA vaccines? Give two examples of such vaccines. Discuss their advantages.
Answer : Recombinant DNA vaccines are made up of a small circular DNA (plasmid) that has very tiny piece of pathogen DNA incorporated in it to produce one or two specific proteins of the pathogen. This recombinant DNA is introduced in to the bacteria or yeast cells, where it can use cell’s machinery to produce polypeptides of pathogen. These are used as vaccine to trigger a range of immune responses. Vaccines produced by using this approach allow large scale production. e.g., (i) Hepatitis-B vaccine produced from yeast. (ii) Bird flu DNA vaccine. Advantages (i) Recombinant DNA vaccines are advantageous over killed or attenuated vaccines since, they does not get virulent or mutated again as it is seen in case of attenuated vaccines. (ii) Secondly these are highly pure, specific and elicits strong immune response.

Question. Explain the role of the following in providing defence against infection in human body:
(i) Histamines
(ii) Interferons
(iii) B-cells
Answer : (i) Histamines: These are chemicals which cause inflammatory responses.
(ii) Interferons: These are glycoproteins which protect non-infected cells from further viral infection.
(iii) B-cells: These produce proteins called antibodies in response to pathogens into the blood to fight with them.

Question. (a) It is generally observed that the children who had suffered from chicken-pox in their childhood may not contract the same disease in their adulthood. Explain giving reasons the basis of such an immunity in an individual. Name this kind of immunity.
(b) What are interferons? Mention their role. 
Answer : (a) The first infection of chicken pox produces a primary response and antibodies are generated against chicken pox virus, subsequent encounter with the same virus elicits a highly intensified secondary response, due to the memory cells formed during the first encounter.
This kind of an immunity is active immunity.
(b) Proteins secreted by viral infected cells, which protects non-infected cells from viral infection are called interferous. When a-interferon is given to cancer patient it activates immune system and destroys tumour.

Question. Many microbial pathogens enter the gut of humans along with food. What are the preventive barriers to protect the body from such pathogens? What type of immunity do you observe in this case? 
Answer : Preventive barrier to protect body are:
(i) The mucus coating of the epithelium lining of the gut helps in trapping microbes entering the body.
(ii) Saliva in the mouth and hydrochloric acid in gastric juice secreted by stomach prevent microbial growth.
This type of immunity is innate immunity.

Question. A person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air, identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions. 
Answer : The condition is called allergy. Mast cells are responsible for such reactions.
To avoid such reactions following precautions must be taken.
(i) Use of drugs like antihistamine, adrenaline and steroids quickly reduces the symptoms.
(ii) Avoid contact with substances to which a person is hypersensitive.

Question. Your classmate complains of headache and cough. The doctor confirms that he is suffering
from Pneumonia and not common cold, on the basis of certain symptoms. List these symptoms.
Mention any two precautions to be followed to prevent the spread of this disease.
Answer : Doctor confirms pneumonia on the basis of the following symptoms—fever/chills/grey-blue lips and finger nails (any two).
It is not common cold as the following symptoms are not observed - Nasal congestion/sore throat/hoarseness (any two).
Precautions to be followed are:
(i) Cover the nose when near the patient.
(ii) Do not share glasses and utensils or articles used by the infected person

Question. During a school trip to ‘Rohtang Pass’, one of your classmate suddenly developed ‘altitude sickness’. But, she recovered after sometime.
(a) Mention one symptom to diagnose the sickness.
(b) What caused the sickness?
(c) How could she recover by herself after sometime? 
Answer : (a) Nausea/fatigue/heart palpitation
(b) The sickness was caused due to low atmospheric pressure at high altitude because of which the body was deprived of oxygen.
(c) The body compensates low oxygen availability by increasing RBC production decreasing the binding capacity of haemoglobin and by increasing breathing rate.

Question. A heavily bleeding bruised road accident victim was brought to a nursing home. The doctor immediately gave him an injection to protect him against a deadly disease.
(a) Write what did the doctor inject into the patient’s body.
(b) How do you think this injection would protect the patient against the disease?
(c) Name the disease against which this injection was given and the kind of immunity it provides. 
Answer : (a) Tetanus antitoxins/Tetanus toxoid.
(b) The preformed antibody injected act on the pathogen immediately to provide protection.
(c) This injection was given against tetanus and it provides passive immunity.

Question. To which category of cells do B-cells and T-cells belong? How do they differ from each other
with reference to their formation and response to antigens?
Answer : B-cells and T-cells belong to the category of lymphocytes, i.e., leucocytes (WBC).

Question.  What is the basic principle of vaccination? How do vaccines prevent microbial infections?
Name the organism from which hepatitis B vaccine is produced.
Answer : Principle of vaccination is based on the property of ‘memory’ of immune system. In vaccination, a preparation of antigenic proteins of pathogens or inactivated/live but weakened pathogens is introduced into the body. The antigens generate primary immune response by producing antibodies along with forming memory B-cells and T-cells. When the vaccinated person is attacked by the same pathogens, second time/subsequent time the existing memory B-cells and T-cells recognise the antigen and overwhelm the invaders with massive production of lymphocytes and antibodies. Hepatitis B vaccine is produced from yeast.

Question. The immune system of a person is suppressed. In the ELISA test, he was found positive to a pathogen.
(a) Name the disease the patient is suffering from.
(b) What is the causative organism?
(c) Which cells of the body are affected by the pathogen? 
Answer : (a) The disease is AIDS.
(b) The causative organism is Human Immunodeficiency Virus.
(c) It affects or destroys helper T-cells.

Question. On a visit to a Hill station, one of your friend suddenly become unwell and felt uneasy.
(a) List two symptoms you would look for the term it to be due to allergy.
(b) Explain the response of the body to an allergen.
(c) Name two drugs that can be recommended for immediate relief.
Answer : (a) Sneezing, watery eyes, running nose and difficulty in breathing are symptoms of allergy.
(b) In response to an allergen, the body releases antibodies of IgE type.
(c) Antihistamine, adrenalin, steroids.

Question. Name the cells HIV (Human Immunodeficiency Virus) gains entry into after infecting the human body. Explain the events that occur in these cells. 
Answer : HIV virus gains entry into Macrophages and (Helper) T-lymphocytes after getting into the human body.
Events that occur in the cells are:
(i) Viral RNA forms DNA by reverse transcription using the enzymes reverse transcriptase and directs the infected cells to produce viral particles.
(ii) Macrophages continue to produce viral particles and function as HIV factories.
(iii) The viral particles simultaneously enters into helper T-lymphocytes, replicates and produce viral progenies.
(iv) The number of T-lymphocytes progressively decreases in the body of the infected person.
(v) During this person suffers from bouts of fever, weight loss. Also decrease in the number of cells leads to weakening of immune system.

Question. Prior to a sports event, blood and urine samples of sports persons are collected for drug tests.
(a) Why is there a need to conduct such tests?
(b) Name the drugs the authorities usually look for.
(c) Write the genetic names of two plants from which these drugs are obtained.
Answer : (a) Such tests are conducted to detect drug abuse to ensure fair game.
(b) The authorities look for cannabinoids, cocaine, coca alkaloid, coke, crack, hashish, charas, ganja and hemp plant extract.
(c) These drugs are obtained from Cannabis, Atropa, Erythroxylum, Datura. (Any two)

Question. A farmer while working on his farm was bitten by a poisonous snake. The workers in the farm immediately rushed him to the nearby health centre. The doctor right away gave him an injection to save his life. What did the doctor inject and why? Explain. 
Answer : The doctor injected an antivenom. The antivenom contains preformed antibodies which when injected act on the pathogen immediately provide protection by providing passive immunity.

Question. (a) Why is there a fear amongst the guardians that their adolescent wards may get trapped in drug/alcohol abuse?
(b) Explain ‘addiction’ and ‘dependence’ in respect of drugs/alcohol abuse in youth.
Answer : (a) Adolescents are easily affected by (or are vulnerable to) peer pressure. Curiosity, need for adventure and excitement, and experimentation constitute common causes for motivation. A child’s natural curiosity motivates him/her to experiment. Television, movies, newspapers, internet also promote drug use.
(b) Addiction is the psychological attachment to certain effects such as euphoria or temporary feeling of well-being.
Dependence is the tendency of the body to show withdrawal syndrome or symptoms if regular doses of drug/alcohol is abruptly discontinued.

Question. A group of youth were having a ‘rave party’ in an isolated area and was raided by police.
Packets of ‘smack’ and syringes with needles were found littered around.
(a) Why is taking ‘smack’ considered an abuse?
(b) Write the chemical name of ‘smack’ and the name of its source plant.
(c) Syringes and needles used by the youth for taking the drug could prove to be very fatal.
Why? 
Answer : (a) Taking smack is considered as abuse because it is highly addictive. It is a depressant and slows down body functions. It causes psychological and physical dependance.
(b) Its chemical name is diacetylmorphine and is obtained from poppy plant, Papaver Somniferum.
(c) Drugs taken intravenously (direct injection into the vein using a needle and syringe) are much likely to acquire serious infections like AIDS and hepatitis B. The viruses, which are responsible for these diseases are transferred from one person to another by sharing infected needles and syringes.

Question. Write the source and the effect on the human body of the following drugs:
(i) Morphine (ii) Cocaine (iii) Marijuana 
Answer : (i) Morphine: It is obtained from poppy plant Papaver somniferum. It binds to specific opioid receptors present in central nervous system and gastrointestinal tract.
(ii) Cocaine: It is obtained from coca plant Erythroxylum coca. It interferes with the transport of the neurotransmitter dopamine.
(iii) Marijuana: It is obtained from Cannabis sativa. It affects the cardiovascular system of the body.

Important Notes for Class 12 Biology Chapter 8 Human Health and Disease

Health

According to World Health Organisation (WHO), health is a state of complete physical, mental and social well-being and not merely the absence of disease or physical fitness. Health is mainly affected by
- Genetic disorders which the child inherits from parents by birth and deficiencies with which a child is born.
- Infections caused by pathogens.
- Lifestyle including the food and water we take, rest and exercise, habits that we have or lack, etc.

Disease

The condition of improper functioning or any condition which interferes with the normal functioning of one or more organ or organ systems of the body and causes disorder of mind or body is called disease. It is characterised by various signs and symptoms.

Types of Diseases

Diseases can be classified as shown below
1. Congenital diseases These diseases are present in human since birth (genetic disorders) or are caused due to mutation, e.g. Down’s syndrome, sickle-cell anaemia, etc.
2. Acquired diseases These diseases develop after birth and are not transferred from parents to offspring.

Acquired diseases are further categorised into
(i) Infectious diseases or Communicable diseases These diseases are easily transmitted from a diseased person to a healthy person either by direct transmission or by indirect transmission. The infectious diseases are very common, e.g. common cold, etc.
(ii) Non-infectious diseases or Non-communicable diseases These diseases cannot be transmitted from a diseased person to a healthy person. These diseases occur either due to nutritional deficiencies or malfunctioning of organs, e.g. cancer, diabetes, etc.

Common Infectious Diseases in Humans
Infectious diseases occur either by pathogen which cause disease in human, e.g. bacteria, viruses, fungi, protozoans, helminthes, etc., or by vectors which spread diseases as they act as carriers to transmit the pathogen from an infected person to a healthy person, e.g. female Anopheles mosquito.

Some common diseases and their pathogenic members are discussed as follows

Bacterial Diseases

Some common bacterial diseases are as follows
1. Typhoid is caused by a bacterium called Salmonella typhi. S. typhi enters the small intestine through contaminated food and water and migrates to other organs through blood.
Symptoms are high fever (39-40°C), weakness, stomach pain, constipation, headache and loss of appetite. In severe cases, intestinal perforation and death may occur.
Widal test is the confirmatory test for diagnosis of typhoid.
2. Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae. These bacteria infect alveoli of the lungs. The alveoli get filled with fluid which causes decrease in respiratory efficiency of the lungs.
Pneumonia spreads by inhaling droplets/aerosol from infected individuals, sharing glasses and utensils with an infected person.
Symptoms are fever, chills, cough, headache, etc. In severe cases, the lips and finger nails may turn grey-bluish in colour.
3. Plague is caused by Pasteurella/Yersinia pestis and is also called black death.
4. Diphtheria is caused by Corynebacterium diphtheriae and is characterised by difficulty in breathing due to infection in the mucous membrane of upper respiratory tract.

Viral Diseases

Some common viral diseases are as follows
1. Common cold occurs due to a group of viruses called rhinoviruses. These viruses infect the nose and the respiratory passage, but not the lungs.
The infection occurs when droplets from cough or sneeze of an infected person are either inhaled directly or transmitted through contaminated objects such as pen, books, cups, computer’s keyboard or mouse, etc. Symptoms include nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc., which generally last for 3-7 days.

2. Dengue is caused by Flavivirus and transmitted by Aedes aegypti mosquito bite.
Symptoms are high fever, severe front headache, joint pain, nausea and vomiting. Treatement for dengue is provided through analgesic medicines as not a vaccine is available for its treatment yet. Dengue can be prevented by elimination of mosquitoes and their eggs.

3. Chikungunya is caused by chikungunya virus and is transmitted by Aedes aegypti mosquito bite.
Symptoms include onset of fever, crippling joint pain, lymphadenopathy, etc.
Chikungunya can be prevented by elimination of mosquitoes and their eggs.

Protozoan Diseases
Some common protozoan diseases are as follows
1. Malaria is caused by different species of the protozoan Plasmodium (vivax, malariae and falciparum). Its transmitting agent is female Anopheles mosquito that transfers the sporozoites of Plasmodium.

Different species of Plasmodium (P. vivax, P. malariae and P. falciparum) are responsible for different types of malaria as given below
Plasmodium species Types of malaria
P. vivax            Benign tertian malaria
P. falciparum    Malignant/pernicious malaria (Most serious)
P. malariae       Quartan malaria
P. ovale            Mild tertian malaria

The life cycle of Plasmodium in its host(s) is described below

(i) Plasmodium enters the human body as sporozoites through the bite of an infected female Anopheles mosquito.
(ii) These sporozoites reach the liver through blood and multiply asexually within the liver cells and attack the Red Blood Cells (RBCs) where they multiply again resulting in their rupture.
(iii) The rupturing of RBCs is associated with the release of a toxin called haemozoin, which is responsible for the high fever recurring every 3/4 days and chill (shivering).
(iv) Gametocytes (sexual stages) develop in the RBCs of human host.
(v) The gametocytes of parasite then enters the mosquito’s body alongwith the blood when female Anopheles mosquito bites the infected person.
(vi) Further development occurs in the stomach wall of the mosquito and the gametes fuse to form a zygote.
(vii) The zygote undergoes further development in the body of the mosquito to form sporozoites.
(viii) These sporozoites are then transported and stored in its salivary glands and are transferred into another human body through saliva.

Symptoms include influenza like illness, shaking chills,headache, muscle ache, nausea, vomiting and diarrhoea.Malaria can also lead to anaemia and jaundice and can also be life-threatening if left untreated.

2. Amoebiasis (amoebic dysentery) is caused by an intestinal endoparasite, Entamoeba histolytica, which is a protozoan parasite of the large intestine of humans.Carrier of pathogens is housefly. It transmits the parasite from faeces of an infected person to the food. Infection takes place through the contaminated food and water.
Symptoms are abdominal pain, constipation, cramps, faeces with excess mucus and blood clots.

Helminthic Diseases

Some common helminthic diseases are as follows
1. Ascariasis is caused by an intestinal endoparasite of human, Ascaris lumbricoides commonly called as roundworm. Infection occurs as the eggs of parasite excreted along with faeces of infected person, contaminate water and soil. Infection reaches human beings through contaminated vegetables, fruits and water.
Symptoms are abdominal pain, indigestion,muscular pain, fever, anaemia, nausea, headache and blockage of intestinal passage.
2. Filariasis/Elephantiasis is caused by filarial worms Wuchereria bancrofti and Wuchereria malayi. Culex mosquito (female) is the vector.
Symptoms are chronic inflammation of organs in which they live, blockage of lymph vessels of lower limbs resulting in swelling. Genital organs also get affected leading to their deformation.

Fungal Disease

Common fungal disease in humans is ringworm.
Ringworm is caused by fungi of the genera–
Microsporum, Trichophyton and Epidermophyton.Infection occurs through contact with an infected person or from soil, through the use of towels, clothes, combs, etc., of an infected person.
Symptoms are appearance of dry, scaly lesions on various parts of the body such as skin, nails and scalp accompanied by intense itching.
Heat and moisture help these fungi to grow in regions like folds as in groin or between the toes.

Prevention and Control of Infectious Diseases

Maintenance of personal and public hygiene is extremely important for prevention and control. Some of the preventive measures that can be taken are as follows

1. For personal hygiene Keeping the body clean, consumption of clean drinking water, food, vegetables, fruits, etc.
2. For public hygiene Proper disposal of waste and excreta, periodic cleaning and disinfection of water reservoirs, pools, cesspools and tanks and observing standard practices of hygiene in public catering.
3. For vector borne diseases such as malaria Eradication of vectors and destroying their breeding sites, e.g. using mosquito nets and repellents, avoiding stagnation of water, regular cleaning of coolers, etc., introducing fishes like Gambusia in ponds that feed on mosquito larvae, spraying of insecticides in ditches, drainage areas and swamps, etc.
4. For air-borne diseases Avoid contact with infected persons or their belongings.
5. Vaccination and immunisation These programmes for diseases should be strictly followed.

Immunity

The ability of the body (host) to fight against the disease causing agents is called immunity. It is of two types as shown below

Innate Immunity
It refers to non-specific type of defence elements with which an individual is born and which are always available to protect the body. It is a non-specific type of defence. It consists of four types of barrier systems that prevent the entry of pathogen or foreign element into the body.

Types of Barriers in Innate Immunity

Various types of barriers are as given below

(i) Physical barriers Skin is the first line of defence. It prevents the entry of the pathogens into the body. Mucus coating of epithelium lining the respiratory, gastrointestinal and urogenital tracts also helps in trapping microbes.
(ii) Physiological barriers Tears from the eyes, saliva in the mouth, acid in the stomach, etc., prevent the growth of microbes.
(iii) Cellular barriers These include the special types of cells in our body which kill the disease causing agents. These are WBCs like Poly Morpho Nuclear Leukocytes (PMNL–neutrophils), monocytes and natural killer cells (type of lymphocytes) in the blood and macrophages in tissues.
(iv) Cytokine barriers Cells which are virus-infected release proteins called interferons that protect non-infected cells from further viral infection.

Acquired Immunity

It is pathogen specific immunity. It is not present from birth and develops during an individual’s lifetime. This type of immunity is acquired, either by encountering the disease or by vaccination. It has the following characters
(i) Specificity It has the ability to distinguish many different foreign molecules.
(ii) Memory It is a unique feature, which helps in producing an intensive secondary/ anamnestic response when the pathogen attacks the second time.
(iii) Discrimination between self and non-self This type of immunity is able to recognise and respond to foreign molecules (non-self) and can avoid response to those molecules that are present within the body (self).

Types of Acquired Immunity
Acquired immunity can be classified as

Active Immunity
It is the immunity developed by the body when it is exposed to the antigens which may be in the form of living or dead microbes or other proteins. Antibodies are produced by the body in this case. Introduction of pathogens or microbes either during immunisation or by any infection induces active immunity. It is slow, but long lasting and has no side effects.
This immunity may be
(i) Artificial immunity developed by vaccination.
(ii) Natural immunity developed during natural infection.

Passive Immunity
It is the immunity bestowed by antibodies that are directly given to the body. It is fast but lasts only for few days. Some examples of passive immunity are
(i) Antibodies received by foetus from mother through placenta.
(ii) Antibodies in the colostrum (IgA rich). Colostrum is a yellowish fluid secreted by mother during the initial days of lactation.

Immune Responses

Following are two major types of immune responses
1. Primary response It is the response generated when a body encounters a pathogen for the first time. It is of low intensity. After every primary response, cell memory stores the details of the encounter.
2. Secondary/Anamnestic response Subsequent encounters of the same pathogen elicits secondary response. It is highly intense. The memory of the first encounter helps in the intense secondary response. It has the capacity to distinguish between self and foreign molecules/cells.
Primary and secondary responses are carried out with the help of two types of lymphocytes, i.e. B-lymphocytes and T-lymphocytes which are classified as

Humoral Immune Response
It is mediated immune response. It includes
(i) B-lymphocytes or B-cells which produce an army of proteins called antibodies in response to pathogens.
These antibodies are found in blood.
(ii) T-lymphocytes or T-cells help B-lymphocytes to produce antibodies.

Cell-Mediated Immune (CMI) Response
- It is mediated by T-lymphocytes. It plays an important role in organ transplantation and is responsible for body’s ability to differentiate between ‘self’ and ‘non-self’.
- In case of transplantation, the chances of graft rejection are very high. Hence, tissue matching and blood group matching are essential before transplantation of any organ or tissue. Even after successful transplant, the patient has to take immuno-suppressants throughout his/her life.
There are two groups of T-lymphocytes responsible for CMI
(i) Cytotoxic/Killer T-cells which kill the specific target cells by a variety of mechanisms.
(ii) Helper T-cells which activate the specific B-cells to produce antibodies.

Antigens and Antibodies

Antigens (Immunogens) These are substances which when enter the body, stimulate the production of antibodies.Antibodies These are immunoglobulins (class of proteins) produced in response to antigenic stimulation.
Each antibody molecule has four peptide chains, out of which; two small chains are called Light (L) chains and two large chains are calledHeavy (H) chains.

An antibody is represented asH2L2 . In our body, different types of antibodies are produced such as IgG, IgA, IgM, IgE and IgD.

Types of Antibodies
Types 

IgG
- Most prevalent class of antibody constitute, 75-80% of total antibodies.
- Protects against fungi, bacteria, toxins, etc.
- It can cross placenta from mother to child and provides immune protection to newborns.
- Responsible for Rh-factor in blood.

IgA
- Second most prevalent antibody.
- It is about 15% of the total antibodies.
- Secreted through parts lined by mucous system.
- Found in secretions from nose, eyes, lungs and digestive tract, saliva, tears, etc.
- Also found in colostrum, i.e. breast milk for newborn’s immune protection.

IgM
- Third most common antibody.
- It constitutes 5-10% of total antibodies.
- They are first to be produced in response to encounter with a pathogen.
- Responsible for blood transfusion reactions in ABO blood system.

IgE
- The least common antibody.
- It makes upto only 0.002% of total antibodies and is involved in allergic reactions.

IgD
- Their function is not well understood yet.

Vaccination and Immunisation

The basic principle of immunisation is based on the property of memory of the immune system. In vaccination, an antigen or antigenic protein or pathogen which is in inactive form is introduced in the body which induces very mild immune response. The vaccine thus, generates antibodies that neutralise pathogen during actual infection. It also generates memory B- and T-cells that recognise the pathogen on subsequent exposure and elicit a massive immune response.

Recombinant DNA Vaccine

Recombinant DNA technology has led to the production of antigenic polypeptides of pathogen via bacteria or yeast cells. It helps in the production of recombinant DNA vaccines on a large scale, e.g. hepatitis-B vaccine (produced from yeast). The vaccines contain a specific gene (segment of DNA). These vaccines are more advantageous as they are pure, specific, etc.

Passive Immunisation

It refers to the introduction of antibodies or antitoxins directly for quick immune response, e.g. in tetanus, preformed antibodies are directly injected and in case of snake bites, antitoxin (contain antibodies to the toxin) against venom is directly given.

Allergies

l The exaggerated or hypersensitive response of the immune system to certain agents in the environment is called allergy and its causing elements are called allergens. Dust, mites, pollens, animal dander (old skin scales which are constantly shed), etc., are some common allergens. The antibodies produced in response to allergens are of IgE type.
l Symptoms of allergic reaction includes sneezing, watery eyes, rashes, running nose, difficulty in breathing, etc.
l Allergy occurs due to the release of chemicals like histamine and serotonin from the mast cells. Drugs like anti-histamine, adrenaline and steroids quickly reduce the symptoms of allergy.
l Now-a-days, allergies are very common especially in children of metropolitan cities which is a result of high sensitivity and lowering of immunity. It is due to the protected environment provided early in life.
l For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens and the reactions are studied.

Autoimmunity
It is the state, where body loses the ability to distinguish between self and non-self cells. The body’s immune system goes off the track and starts destroying self cells and molecules. This causes damage to the body resulting in autoimmune diseases, e.g. rheumatoid arthritis, Addison’s disease, Hashimoto’s disease, etc.

Immune System in the Body

The main function of immune system is to recognise the foreign molecules (antigens), respond to them and to keep memory of these encounters. It also plays a crucial role in organ transplants, allergic reactions and autoimmune diseases. Human immune system consists of antibodies, immune cells, lymphoid organs and tissues. It has unique features of memory and identification of a large number of pathogens.

Lymphoid Organs

Organs where lymphocytes originate, proliferate and get matured are known as lymphoid organs. They can be categorised as

Primary Lymphoid Organs
In primary lymphoid organs, immature lymphocytes differentiate to mature antigen sensitive lymphocytes and after maturation, lymphocytes migrate to secondary lymphoid organs.

The two primary lymphoid organs are
(i) Bone marrow It is the main lymphoid organ where all the blood cells including lymphocytes are produced. It is the site of B-lymphocytes maturation.
(ii) Thymus It is a lobed organ, located near the heart and beneath the breast bone. It is large at the time of birth, but with age, the size keeps on reducing and becomes very small on attaining puberty. Growth and maturation of T-lymphocytes takes place here.

Secondary Lymphoid Organs
These organs provide the sites for the interaction of lymphocytes with the antigen, which then proliferate to become effector cells.
The secondary lymphoid organs are
(i) Spleen It is a large bean-shaped organ containing lymphocytes, phagocytes and large number of erythrocytes. It filters the blood by trapping blood-borne microorganisms.
(ii) Lymph nodes These are small solid structures located at different points along the lymphatic system. Their function is to trap the microorganisms or other antigens that enter the lymph and tissue fluid. The trapped antigens in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response.
(iii) Mucosal Associated Lymphoid Tissue (MALT) It is located within the lining of major tracts in the body like respiratory, digestive, urogenital tracts. MALT constitutes about 50% of the lymphoid tissue in human body.

Note (i) Bursa of fabricus is the primary lymphoid organ in birds that is considered equivalent to mammal’s bone marrow.
(ii) Both bone marrow and thymus provide micro-environments for the development and maturation of T-lymphocytes.
(iii) Peyer’s patches of small intestine, tonsils and appendix are also considered as secondary lymphoid organs.

Acquired Immuno Deficiency Syndrome (AIDS)

- It refers to the deficiency of the immune system, acquired during the lifetime of an individual, indicating that it is not a congenital disease. It was first reported in 1981 in USA.
- The causative agent is Human Immunodeficiency Virus (HIV). It belongs to the group of viruses called retrovirus. It has single-stranded RNA genome enclosed in an envelope.
- HIV is transmitted by
– Sexual contact with an infected person.
– Transfusion of contaminated blood.
– Sharing infected needles.
– Infected mother to unborn child through placenta
Individuals who are susceptible to infection are
– Drug addicts due to intravenous drug injections.
– Involved with multiple sexual partners.
– Require repeated blood transfusion.
– Children born to HIV positive mother.
- HIV/AIDS spreads only through body fluids. There is always a time-lag between the infection and appearance of AIDS symptoms, i.e. it varies from a few months to many years (usually 5-10 years).

Mode of HIV Infection

Virus enters the macrophage after entering the body of a person. RNA gets replicated to form viral DNA by enzyme reverse transcriptase. Viral DNA gets incorporated into the host cell DNA and directs the infected cells to produce new viruses. Macrophages continue to produce virus particles and act like HIV factory.
These virus particles enter helper T-lymphocytes (TH cells) in the blood, where they continue to replicate and produce viral progeny. The number of helper T-lymphocytes progressively decreases in the body of the infected people.
As the number of T-cells decrease, immunity also decreases. As a result, the person cannot produce any immune response even against common bacteria like Mycobacterium, parasites like Toxoplasma viruses and fungi. During this period, person suffers from fever, diarrhoea and weight loss.

Treatment and Diagnosis
Enzyme Linked Immuno-Sorbent Assay (ELISA) is used as a diagnostic test for AIDS.
Treatment of AIDS with anti-retroviral drugs is only partially effective. These can only prolong the life of the patient, but cannot prevent death.

Prevention of AIDS

As AIDS has no cure, prevention is the best option.
Preventive measures for HIV infection are
- Ensure use of disposable syringes and needles.
- Ensure keeping blood banks safe from HIV.
- Free distribution of condoms.
- Prevention of drug abuse.
- Discouraging unsafe sex and encouraging regular checkups.

To prevent the spread of HIV infection WHO has started many programmes. In India organisations like National AIDS Control Organisation (NACO) and other NGO’s educate peoples about AIDS in rural and urban areas.

Cancer
It is the major cause of death all over the globe. It is caused by the breakdown of normal regulatory mechanisms of cell growth.
Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibit their uncontrolled growth. Cancerous cells, however lose this property and continue to divide giving rise to masses of cells called tumours.
Tumours are of two types, i.e. benign and malignant.
(i) Benign tumours normally remain confined to their original location and do not spread to other parts of the body and cause little damage.
(ii) Malignant tumours are a mass of proliferating cells called neoplastic or tumour cells. These cells grow very rapidly, invading and damaging the surrounding normal tissues. As these cells actively divide and grow, these also starve the normal cells by competing for vital nutrients. Cells sloughed from malignant tumours reach distant sites through blood flow and wherever they get lodged in the body, they start a new tumour there. This property is called metastasis.

Causes of Cancer
Carcinogens are cancer-causing agents. These are
(i) Chemical Cigarette smoke (cause lung cancer) benzopyrene, dyes, paints, etc.
(ii) Biological Oncogenic viruses, some parasites, etc. Cancer causing viruses called oncogenic viruses have genes called viral oncogenes. Normal cells have genes called cellular oncogenes (C-onc) or proto-oncogenes which are present in inactive state, but under certain conditions (like mutation) get activated to cancer-causing oncogenes.
(iii) Physical Ionizing radiations like X-rays and g-rays, non-ionizing radiations like UV-rays (cause DNA damage leading to neoplastic transformation).

Cancer Detection and Diagnosis
Cancer can be detected by the following methods
(i) Blood and bone marrow tests To know elevation in number of cell counts.
(ii) Biopsy of a piece of suspected tissue done by cutting thin sections, which are then stained and examined under microscope.
(iii) Radiography By X-rays to detect cancer of the internal organs.
(iv) Computed tomography Using X-rays to generate a 3D image of internal tissue.
(v) Resonance imaging involves use of non-ionizing radiation and strong magnetic field to detect pathological and physiological changes in living tissue.
(vi) Monoclonal antibodies Against cancer-specific antigens are also used for cancer detection.
(vii) Molecular biology Technique to detect genes in individual with inherited susceptibility to certain cancers.

Treatment of Cancer
Treatment of cancer involves the following methods
(i) Surgery Tumours are removed by surgery to check further spread of cancer cells.
(ii) Radiation therapy Tumour cells are irradiated by a lethal dose of radiation while protecting the surrounding normal cells.
(iii) Chemotherapy Several chemotherapeutic drugs are used to kill cancer cells. But, their side effects like hair loss, anaemia is also reported.
(iv) Immunotherapy Biological modifiers like a-interferons are used to activate the immune system and help in destroying the tumour.

Drugs and Alcohol Abuse

The use of drugs and alcohol has risen especially among the youth. This is a cause of concern as it results in many harmful effects.
The drugs which are commonly abused are as follows

Opioids
These are the drugs which bind to specific opioid receptors present in our central nervous system and gastrointestinal tract. These have narcotic, analgesic, sedative and astringent effects.

Some of them are
Heroin is a common opioid and is also called as smack. It is chemically diacetylmorphine, white, odourless, bitter crystalline compound.
- It is obtained from the acetylation of morphine, which is extracted from the latex of poppy plant, Papaver somniferum.
- It is taken either by snorting or through injection.
- Heroin is a depressant which slows down the body functions.
Morphine is an effective sedative, painkiller and very useful in patients who have undergone surgery.

Cannabinoids
These are a group of chemicals which interact with cannabinoid receptors present mainly in brain. Cannabinoids are obtained from the inflorescence of the plant Cannabis sativa. Leaves, flower tops, resins of C. sativa in various combinations produce hashish, charas, marijuana and ganja.
These are inhaled or ingested orally. These drugs affect cardiovascular system of the body.

Coca Alkaloids or Cocaine
It has a potent stimulating action on the central nervous system, producing a sense of euphoria and increased energy. Cocaine is derived from the leaves and young branches of a South American plant called Erythroxylum coca.
Its mode of intake is either sniffing or snorting. It is a strong stimulant and when taken in overdose causes headache, convulsions, hallucination and death due to cardiovascular or respiratory failure.

Hallucinogens
These are psychedelic drugs which affect the cerebrum and sense organs. These are obtained from plants like Atropa belladonna and Datura species. Lysergic acid diethylamide (LSD) is derived from the fungus, Claviceps purpurea. Effect of these drugs occurs on thoughts, feelings and perceptions of an individual. Drugs like barbiturates, amphetamines, benzodiazepines, etc., normally used as medicines.

Tobacco
It contains nicotine which stimulates the adrenal gland to release adrenaline and nor-adrenaline which in turn increases the blood pressure and heart rate. It is obtained from tobacco plant.
Its mode of intake is smoking, chewing or can be used as a snuff.
Tobacco can induce lung cancer, bronchitis, emphysema, coronary heart disease, cancer of throat, oral cancer, urinary bladder cancer, etc.
Smoking of tobacco leads to increase in carbon monoxide content of blood and reduces the concentration of haem-bound oxygen. This leads to oxygen deficiency in the body.

Adolescence and Drug/Alcohol Abuse

Adolescence is the period during which a child becomes mature in terms of his/her attitudes and beliefs for independent participation in the society.
Age between 12-18 years is called adolescent period.
Adolescence is accompanied by several biological and behavioural changes. It is a vulnerable phase of mental and psychological development of an individual.
In this age use of drugs or alcohol occurs out of curosity or experimentation which later turns to addiction.

Addiction and Dependence

Addiction is the psychological attachment to certain effects such as euphoria and a temporary feeling of well-being associated with drugs and alcohol.
Dependence on drug/alcohol is the tendency of the body to manifest a characteristic and unpleasant withdrawl syndrome, if regular dose of drugs/alcohol is discontinued abruptly. Withdrawl symptoms are characterised by anxiety, shakiness, nausea and sweating.

Effects of Drug/Alcohol Abuse

The common warning signals of drug/alcohol addiction are
- Drop in academic performance.
- Isolation from family and friends.
- Lack of interest in personal hygiene.
- Aggressive and rebellious behaviour.
- Reckless behaviour, vandalism and violence.

Prevention and Control

The preventive measures are
- Avoid undue peer pressure.
- Accept failures and disappointments as part of life.
- Seek help from parents and peers.
- Seek professional and medical help for de-addiction.
- Look for danger signs.