Diseases and Immunity Syllabus PDF

Diseases and Immunity  Syllabus- Disease 1 Describe a pathogen as a disease-causing organism 2 Describe a transmissible disease as a disease in which the pathogen can be passed from one host to another 3 Understand that a pathogen may be transmitted: (a) through direct contact, including th...

Diseases and Immunity  Syllabus- Disease 1 Describe a pathogen as a disease-causing organism 2 Describe a transmissible disease as a disease in which the pathogen can be passed from one host to another 3 Understand that a pathogen may be transmitted: (a) through direct contact, including through blood or other body fluids (b) indirectly, including from contaminated surfaces or food, from animals, or from the air 4 Describe the human body’s barriers to the entry of pathogens, limited to: skin, hairs in the nose, mucus, stomach acid  Syllabus- Disease 5 Understand the role of the mosquito as a vector of disease 6 Describe the malarial pathogen as an example of a parasite and explain how it is transmitted 7 Describe the control of the mosquito that transmits malaria with reference to its life cycle 8 Explain that human immunodeficiency virus (HIV) is a viral pathogen 9 Describe how HIV is transmitted 10 Understand that HIV infection may lead to Acquired Immune Deficiency Syndrome (AIDS) 11 Describe the methods by which HIV may be controlled 12 Describe cholera as a disease caused by a bacterium, which is transmitted in contaminated water  Syllabus- Disease 13 Explain the importance of a clean water supply, hygienic food preparation, good personal hygiene, waste disposal and sewage treatment in controlling the spread of cholera (details of the stages of sewage treatment are not required) 14 Explain that the cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, resulting in diarrhoea, dehydration and loss of ions from the blood 15 Describe the effects of excessive consumption of alcohol: reduced self-control, depressant, effect on reaction times, damage to liver and social implications 16 Describe the effects of tobacco smoke and its major toxic components (nicotine, tar and carbon monoxide): strong association with bronchitis, emphysema, lung cancer, heart disease, and the association between smoking during pregnancy and reduced birth weight of the baby  Syllabus- Antibiotics 1 Describe a drug as any substance taken into the body that modifies or affects chemical reactions in the body 2 Describe the use of antibiotics for the treatment of bacterial infection 3 State that antibiotics kill bacteria but do not affect viruses 4 Explain how development of antibiotic- resistant bacteria, including MRSA, can be minimised by using antibiotics only when essential  Syllabus- Immunity 1 Describe active immunity as defence against a pathogen by antibody production in the body 2 State that each pathogen has its own antigens, which have specific shapes 3 Describe antibodies as proteins that bind to antigens leading to direct destruction of pathogens, or marking of pathogens for destruction by phagocytes 4 State that specific antibodies have complementary shapes which fit specific antigens 5 Explain that active immunity is gained after an infection by a pathogen, or by vaccination 6 Outline the process of vaccination: (a) weakened pathogens or their antigens are given (b) the antigens stimulate an immune response by lymphocytes which produce antibodies (c) memory cells are produced that give long-term immunity  Syllabus- Immunity 7 Explain the role of vaccination in controlling the spread of transmissible diseases 8 Explain that passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual, limited to: across the placenta and in breast milk 9 Explain the importance of breast-feeding for the development of passive immunity in infants 10 State that memory cells are not produced in passive immunity 11 Outline how HIV affects the immune system, limited to: decreased lymphocyte numbers and reduced ability to produce antibodies, which weakens the immune system  Pathogens A pathogen is a disease-causing organism Pathogens are passed on from one host to another and therefore the diseases they cause are known as transmissible diseases Pathogens can be passed on from host to host in different ways, including: – Direct contact – the pathogen is passed directly from one host to another by transfer of body fluids such as blood or semen (eg HIV, gonorrhoea, hepatitis B & C) – Indirect contact – the pathogen leaves the host and is carried in some way to another, uninfected individual Transmission  Body’s Defenses 1. Mechanical barriers – structures that make it difficult for pathogens to get past them and into the body a) Skin – covers almost all parts of your body to prevent infection from pathogens. If it is cut or grazed, it immediately begins to heal itself, often by forming a scab. b) Hairs in the nose – these make it difficult for pathogens to get past them further up the nose so they are not inhaled into the lungs 2. Chemical barriers – substances produced by the body cells that trap / kill pathogens before they can get further into the body a) Mucus – made in various places in the body, pathogens get trapped in the mucus and can then be removed from the body (by coughing, blowing the nose, swallowing etc) b) Stomach acid – contains hydrochloric acid which is strong enough to kill any pathogens that have been caught in mucus in the airways and then swallowed or have been consumed in food or water 3. Cells – different types of white blood cell work to prevent pathogens reaching areas of the body they can replicate in a) By phagocytosis – engulfing and digesting pathogenic cells b) By producing antibodies – which clump pathogenic cells together so they can’t move as easily (known as agglutination) and releasing chemicals that signal to other cells that they must be destroyed  Malaria Vector Vectors are living organisms that can transmit infectious pathogens between humans, or from animals to humans. Many of these vectors are bloodsucking insects, which ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later transmit it into a new host. Malaria Malaria is caused by a single-celled parasite of the genus plasmodium. Four kinds of malaria parasites infect humans: Plasmodium falciparum, P. vivax, P. ovale, and P. malariae. The parasite is transmitted to humans through the bite of female Anopheles mosquitoes. Uninfected mosquito: A mosquito becomes infected by feeding on a person who has malaria. Transmission of parasite: If this mosquito bites you in the future, it can transmit malaria parasites to you. In the liver: Once the parasites enter your body, they travel to your liver — where some types can lie dormant for as long as a year. Into the bloodstream: When the parasites mature, they leave the liver and infect your red blood cells. This is when people typically develop malaria symptoms. On to the next person: If an uninfected mosquito bites you at this point in the cycle, it will become infected with your malaria parasites and can spread them to the other people it bites. Transmission  How to prevent spread Use mosquito nets when sleeping in places where malaria is present. Use mosquito repellents after dusk. Use coils and vaporizers. Wear protective clothing. Use window screens. Use larvicides to kill larvae. Remove stagnant water. Use insecticide sprays. Breed fishes for eating eggs in large water bodies (biological control).  Human Immunodeficiency Virus The human immunodeficiency virus (HIV) targets the immune system and weakens people's defense against many infections that people with healthy immune systems can more easily fight off. As the virus destroys and impairs the function of immune cells, infected individuals gradually become immunodeficient. HIV causes decreased lymphocyte numbers and reduced ability to produce antibodies, which weakens the immune system The most advanced stage of HIV infection is acquired immunodeficiency syndrome (AIDS), which can take many years to develop. AIDS is defined by the development of certain cancers and severe infections like TB. Transmission HIV can be transmitted via the exchange of a variety of body fluids from infected people, such as blood, breast milk, semen and vaginal secretions. HIV can also be transmitted from a mother to her child during pregnancy and delivery. Individuals cannot become infected through ordinary day-to- day contact such as kissing, hugging, shaking hands, or sharing personal objects, food or water.  Prevention of AIDS Key approaches for HIV prevention, which are often used in combination, include: Male and female condom use Prevention, testing and counselling for HIV and STIs No sharing of needles or injection equipment Prevent contaminated blood transfusion Prevent contaminated tissue transplant  Cholera A bacterium called Vibrio cholerae causes cholera infection. The deadly effects of the disease are the result of a toxin the bacteria produces in the small intestine. The toxin causes the body to secrete enormous amounts of water, leading to diarrhea and a rapid loss of fluids and salts (electrolytes). Cholera bacteria might not cause illness in all people who are exposed to them, but they still pass the bacteria in their stool, which can contaminate food and water supplies.  How Cholera Spreads A person can get cholera by drinking water or eating food contaminated with cholera bacteria. In an epidemic, the source of the contamination is usually the feces of an infected person that contaminates water or food. The disease can spread rapidly in areas with inadequate treatment of sewage and drinking water. The infection is not likely to spread directly from one  Cholera Toxin Cholera Toxin is a protein toxin, secreted by toxic species of the bacterium. The cholera toxin affects the intestine by activating the chloride channel proteins to open and allowing the movement of chloride ions out of the cell and into the small intestine. This makes the outside of the cell hypertonic (lower water potential) and causing water to get out of the cell through osmosis. Leading to watery diarrhea. This causes dehydration and loss of ions (Chloride and Sodium ion) Prevention CLEAN WATER - CONTAMINATED WATER IS LINKED TO TRANSMISSION OF DISEASES SUCH AS CHOLERA, DIARRHOEA etc - INADEQUATE MANAGEMENT OF URBAN, INDUSTRIAL, AND AGRICULTURAL WASTEWATER MEANS THE DRINKING- WATER OF HUNDREDS OF MILLIONS OF PEOPLE IS DANGEROUSLY CONTAMINATED OR CHEMICALLY POLLUTED. - SEWAGE TREATMENT IS NECESSARY TO PREVENT THESE CONTAMINATED WATER FROM INFECTING POPULATIONS  Alcohol Consumption Alcohol works as a depressant by slowing down body’s reaction. Short term effects  Blackouts- amnesia of events  Loss of self control  Outburst of aggressive behavior  Increased reaction time  Effect on the Liver -Excessive buildup of fat in the liver, also known as fatty liver or hepatic steatosis -Inflammation of the liver or alcoholic hepatitis -Replacement of normal liver  Social Implications Decrease in workplace productivity Domestic violence Violent crimes Financial problems due to excessive spending on alcohol Losing connection with friends and family  Side Effects of Tobacco Smoking LUNG CANCER There are many, approximately 70, chemicals in cigarettes that can increase chances of cancer as they are carcinogenic. HEART DISEASES There are chemicals that can increase blood pressure and increase the load on the heart to pump blood. LUNG DISEASES Emphysema and bronchitis can put pressure on lungs Lung Cancer Smoking During Pregnancy - Premature birth - Miscarriage - Poor neurological development - Retarded growth - Low birth weight  Antibiotics A drug is any substance taken into the body that modifies or affects chemical reactions in the body Some drugs are medicinal drugs that are used to treat the symptoms or causes of a disease - for example antibiotics Antibiotics are chemical substances made by certain fungi or bacteria that affect the working of bacterial cells, either by disrupting their structure or function or by preventing them from reproducing. Antibiotics are effective against bacteria but not against viruses. Antibiotics target processes and structures that are specific to bacterial (prokaryotic) cells; as such they do not generally harm animal cells. Why don't Antibiotics Affect Viruses? Viruses cannot be treated with antibiotics This is because antibiotics work by disrupting cell functions such as respiration, or breaking down the structure of the cell in some way However, viruses do not carry out any cell functions and do not have cell walls, cell membranes or any cell organelles as viruses infect and utilise the machinery of animal cells to reproduce, which are not affected by antibiotics. Therefore the action of antibiotics do not affect them  MRSA Resistance to antibiotics results in antibiotics resistant bacterial infections in hospitals such as MRSA which stands for methicillin resistant staphylococcus aureas. Commonly prescribed antibiotics are becoming less effective due to a number of reasons: – overuse and being prescribed when not really necessary – patients failing to complete the fully prescribed course by a doctor – large scale use of antibiotics in farming to prevent disease when livestock are kept in close quarters, even when animals are not actually sick Ways individuals can help prevent the incidence of antibiotic resistance increasing include: – only taking antibiotics when absolutely essential – when prescribed a course of antibiotics, ensure that the entire course is completed even if you feel better after a few days  Active Immunity Making antibodies and developing memory cells for future response to infection is known as active immunity There are two ways in which this active immune response happens: – The body has become infected with a pathogen and so the lymphocytes go through the process of making antibodies specific to that pathogen – Vaccination Active immunity is slow acting and provides long-lasting immunity  Antibody & Antigen All cells have proteins and other substances projecting from their cell membrane These are known as antigens and are specific to that type of cell Lymphocytes have the ability to ‘read’ the antigens on the surfaces of cells and recognise any that are foreign They then make antibodies which are a complementary shape to the antigens on the surface of the pathogenic cell The antibodies attach to the antigens and cause agglutination (clumping together) This means the pathogenic cells cannot move very easily At the same time, chemicals are released that signal to phagocytes that there are cells present that need to be destroyed Lymphocytes that have made antibodies for a specific pathogen for the first time will then make ‘memory cells’ that retain the instructions for making those specific antibodies for that type of pathogen How Antigens Work  How Does Vaccination Work? Vaccines allow a dead or altered form of the disease- causing pathogen, which contains specific antigens, to be introduced into the body In this weakened state, the pathogen cannot cause illness but can provoke an immune response Lymphocytes produce complementary antibodies for the antigens The antibodies target the antigen and attach themselves to it in order to create memory cells The memory cells remain in the blood and will quickly respond to the antigen if it is encountered again in an infection by a ‘live’ pathogen As memory cells have been produced, this immunity is long-lasting  How does Vaccination Control the Spread of Disease If a large enough percentage of the population is vaccinated, it provides protection for the entire population because there are very few places for the pathogen to breed – it can only do so if it enters the body of an unvaccinated person This is known as herd immunity If the number of people vaccinated against a specific disease drops in a population, it leaves the rest of the population at risk of mass infection, as they are more likely to come across people who are infected and contagious This increases the number of infections, as well as the number of people who could die from a specific infectious disease Herd immunity prevents epidemics and pandemics from occurring in populations This is the reason that many vaccinations are given to children, as they are regularly seen by medical practitioners and can be vaccinated early to ensure the entire vaccinated population remains at a high level In certain instances, vaccination programmes are run with the aim of eradicating certain dangerous diseases, as opposed to controlling them at low levels An example of a disease which has been eradicated as a result of a successful vaccination programme is smallpox  Passive Immunity This is when ready-made antibodies, from another source, are introduced to the body Passive immunity is a fast-acting, short-term defence against a pathogen by antibodies acquired from another individual Example: from mother to infant via breast milk/placenta – this is important as it helps the very young to fight off infections until they are older and stronger and their immune system is more responsive Injected antibodies for certain diseases where the individual is already infected and a fast response is required, like rabies or tetanus The body does not make its own antibodies or memory cells in passive immunity Questions