Why Do We Fall Ill? PDF

CHAPTER – 13 WHY DO WE FALL ILL? ANSWER THE FOLLOWING 1. What do you mean by a disease? Disease literally means being uncomfortable.. 2. How are diseases classified on the basis of duration? Distinguish them. ACUTE DISEASE...

CHAPTER – 13 WHY DO WE FALL ILL? ANSWER THE FOLLOWING 1. What do you mean by a disease? Disease literally means being uncomfortable.. 2. How are diseases classified on the basis of duration? Distinguish them. ACUTE DISEASE CHRONIC DISEASE Diseases that last for only very Diseases that last for a long period of short periods of time are called time, even as much as a lifetime are acute diseases (minor effect). called chronic diseases (major effect) Acute diseases will not cause major Chronic diseases will cause major effect on general health. effect on general health. The patient gets recovered within a The recovery is seldom complete few days after the treatment. even after the treatment. They do not cause drastic ill effect Will affect our learning ability, causes on people’s health. shortness of breath, weight loss, feel tired Examples of acute diseases are - Examples of chronic diseases are – Common cold, Cough etc… Elephantiasis, Tuberculosis etc… 3. Distinguish diseases on the basis of immediate cause. Diseases where microbes or microorganisms are the immediate causes are called infectious diseases. This is because the microbes can spread in the community and the diseases they cause will spread with them. Example – Common cold, Influenza, Chicken pox, Small pox etc… Diseases that are not caused by infectious agents are called non – infectious diseases. Their causes vary, but they are not external causes like microbes that can spread in the community. Instead, these are mostly internal, non – infectious causes. They may be some genetic abnormalities, or they may be caused due to our everyday lifestyle and food habits. Example – Cancer, High blood pressure etc… 4. Classify diseases on the basis of pathogens. Diseases caused by  Virus – Common cold, Influenza, Dengue fever, AIDS.  Bacteria – Typhoid fever, Cholera, Tuberculosis, Anthrax.  Protozoa – Malaria, kala – azar, sleeping sickness.  Worms – Elephantiasis, Ascariasis, Filariasis.  Fungi – many skin infections, Athlete’s foot, Ringworm disease. 5. Why are antibiotics effective against bacterial infection and not against viral? Antibiotics commonly block biochemical pathways important for bacteria. Many bacteria make a cell wall to protect themselves. The antibiotic penicillin blocks the bacterial processes that built the cell wall. As a result, the growing bacteria become unable to make cell walls and die easily. Human cells don’t make a cell wall, anyway so penicillin can’t have side effect on humans. Penicillin will have this effect on any bacteria that use such processes for making cell walls. Similarly many antibiotics work against many species of bacteria rather than simply working against one. But viruses do not use these pathways at all and that is the reason why antibiotics do not work against viral infections. However, if we also get a bacterial infection along with viral cold, taking antibiotics will help. Even then, the antibiotic will work only against the bacterial part of the infection, not the viral infection. 6. Expand SARS, AIDS, HIV SARS – Severe Acute Respiratory Syndrome AIDS – Acquired Immuno Deficiency Syndrome HIV – Human Immuno deficiency Virus 7. Taking antibiotics for cold does not reduce the severity of the disease. Explain. Bacteria build the cell wall to protect themselves. The antibiotics blocks the biochemical processes of these bacteria to build the cell wall. Hence, the bacteria lacks cell wall. It dies. But viruses do not use these pathways at all and that is the reason why antibiotics do not work against viral infections. That is why, taking antibiotics for cold does not reduce the severity of the disease. 8. Explain the different means of spread of diseases. There are different means of spread of diseases – a) Air – borne diseases – Some diseases causing microbes can spread through the air. This occurs through the little droplets thrown out by an infected person who sneezes or coughs. Someone standing close by can breathe in these droplets and the microbes get a chance to start a new infection.  Examples of such diseases are – Common cold, Pneumonia, Tuberculosis etc… b) Water – borne diseases – Diseases that spread through water are called water – borne diseases. This occurs if the excreta from someone suffering from an infectious gut disease, such as cholera, get mixed with the drinking water used by people living nearby. Such diseases are likely to spread in the absence of supplies of safe drinking water. c) Through sexual contact –Sexually transmitted diseases are transmitted by sexual contact from one partner to other. The sexually transmitted diseases are not spread by casual physical contact like handshakes or hugs or sports like wrestling or by any of the other of the ways in which we touch socially. The AIDS virus can also spread through blood – to – blood contact with infected people. Example – AIDS, Syphilis. d) Vector – borne diseases – Diseases that spread through animals or vectors are called vector – borne diseases. These animals carry the infecting agents from a sick person to another potential host. These animals are called intermediaries and are called vectors. The most common vectors are mosquitoes. Example – Dengue, Malaria. 9. What are carriers / vectors? How do they transfer disease causing germs? Give two examples. Many diseases are transmitted by other animals. These animals carry the infecting agents from a sick person to another potential host. These animals are thus the intermediaries and are called vectors. Example – Female Anopheles mosquito Female Aedes mosquito 10. How do microorganisms select different organs where they have to cause different diseases? Different species of microbes seem to have evolved to home in on different parts of the body. In part, this selection is connected to their point of entry. If they enter from the air via nose, they are likely to go to the lungs. An example of this is tuberculosis. If they can enter through mouth, they can stay in the gut lining like typhoid causing bacteria or they can go to the liver, like viruses that causes jaundice. It can also enter the body via sex organs, for example, HIV. 11. While analyzing the signs and symptoms of the disease, we can know the target organ that is affected. Explain. The signs and symptoms of the disease will depend on the tissue or organ which the microbe targets. If the lungs are the target, symptoms will be cough and breathlessness. If the liver is targeted, there will be jaundice. If brain is the target, symptoms such as headaches, vomiting, fits or unconsciousness will occur. 12. How does HIV damage our immune system? HIV goes to the immune system and damage its function. Thus, many of the effects of HIV – AIDS are because the body can no longer fight off the many minor infections that we face every day. Instead, every small cold can become pneumonia. Similarly, a minor gut infection can produce major diarrhoea with blood loss. 13. Severity of disease manifestation depends on the number of microbes in our body. Explain. Severity of disease manifestation depend on the number of microbes in the body. If the number of microbes is very small, the disease manifestation may be minor or unnoticed. But if the number of the same microbes is large, disease can be severe enough to be life threatening. The immune system is a major factor that determines the number of microbes surviving in the body. 14. What is the basis of the principle of immunization? (principle of vaccination) When the immune system first sees an infectious microbe, it responds against it and then remembers it specifically. The next time, the particular microbe or its close relatives enter the body, the immune system responds with even greater vigour. This eliminates the infection even more quickly than the first time around. This is the basis of the principle of immunization. 15. Name the diseases against which we take vaccines. There are vaccines against tetanus, diphtheria, whooping cough, measles, polio and many others. These form the public health programme of childhood immunization for preventing infectious diseases. 16. What are vaccines? / Define vaccines. Vaccines contain dead and weakened or half killed microbes when injected into our body, our body starts producing antibodies which are specific to each microbes. These antibodies will give lifelong immunity power against these dreadful diseases.