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| Frage | Antworten |
| 4.1.1 | Diseases, Prevention & the Immune system |
| What is meant by the term health and disease? | • Health is a state of mental, physical and social wellbeing, not just the absence of disease • Disease Departure from good health due to a malfunction of body or mind, and, which causes symptoms. A condition that impairs the normal functioning of an organism. It can be caused by genetic defects, nutritional deficiencies and environmental factors. Infectious diseases can be passed between people e.g. malaria, HIV & TB. |
| What is meant by the term parasite? | • Parasite an organism which gains from other organisms by living on or in it, causing harm to the host. 1. Live in or on a host 2. It causes harm but does not kill the host 3. They usually benefit by taking nutrition 4. They live all or part of their lives with the host and often unnoticed. E.g. Tapeworm or blood fluke |
| What is meant by the term pathogen? | • A pathogen is an organism which causes disease. |
| What are the four main types of pathogens? | 1. Bacterial pathogens 2. Fungal pathogens 3. Virusal pathogens 4. Protoctistal pathogens |
| Describe the different types of pathogens that can cause communicable diseases in plants and animals. | |
| Describe the means of transmission of bacterial pathogens. | --> The cells may be smaller than eukaryotic cell but they can multiply very rapidly (every 20 minutes suitable conditions) in the human body. --> Their presence causes disease either by damaging cells or releasing toxic waste products --> Examples include cholera caused by Vibrio cholerae and tuberculosis caused by Mycobacterium tuberculosis] |
| Describe the means of transmission of virusal pathogens. | --> Do not have a cellular structure, the basic foundation of life. --> Viruses invade cells and take over genetic machinery, causing the cell to manufacture more copies of the virus, and when the host cell eventually bursts, many new viruses are released. --> Examples include tobacco mosaic virus – the first virus discovery- in plants and the HIV virus. |
| Describe the means of transmission of Fungal pathogens. | --> A fungus can live under the skin. --> It can send out reproductive hyphae which grow to the skin surface, releasing spores, which can cause redness and irritation. --> Examples include Tinea which causes ringworm and athlete’s foot. |
| Describe the means of transmission of Protoctistal pathogens. | --> These organisms enter cells and feed on their contents as they grow. --> Examples include the malarial parasite genus Plasmodium which causes malaria. |
| What is meant by the term transmission? | --> Transmission is when a pathogen is passed from an infected organism to an uninfected organisms. --> aka the manner in which a disease organism is spread. |
| What are vectors? | --> They are organisms, which transmit pathogens fro one organism to another. --> Transmit disease from one host to another. |
| Describe the means of transmission of malaria. | Malaria – malaria is a parasite of mosquitoes which uses humans as a vector to get from on mosquito to another. • Malaria is caused by eukaryotic organisms of the Plasmodium genus, most commonly the P. falciparum. • It is spread by a vector, by the female Anopheles mosquito which carries the Plasmodium from one infected person to another. • The mosquito feeds on blood, as it had adapted mouth organs which have developed into fine tubes to penetrate and draw blood. • A person with malaria has the Plasmodium gametes in their blood, and so when the Anopheles female mosquito sucks the blood, the Plasmodium reproduces sexually in the mosquito and migrates to its salivary gland, where it causes infection of an uninfected person when bitten. • The Plasmodium migrates to the liver when a person is bitten, so that the parasitic stages can multiply, asexually, in the liver and then migrate into the blood, ready to be transmitted to someone else. |
| Describe the global impact of Malaria. | Malaria kills around 3 million each year. Approximately 300 million people are infected by the Plasmodium, but this number is ever-rising. Malaria is limited only to the areas where the Anopheles mosquito can survive, currently only tropical areas, but with the effects of global warming becoming more apparent, it is very possible that soon the disease could spread further up northwards, even affecting Europe. |
| Describe the means of transmission of HIV/AIDS. | • AIDS (acquired immune deficiency syndrome) is caused by the human immunodeficiency virus (HIV). • A person infected with HIV is known as HIV-positive. The virus enters the body and remains largely inactive for a long period of time. • When it becomes active, it destroys T-helper cells. • These cells are an essential component of the immune system, and so the chances of fighting off pathogenic infections are reduced by about 90%. • It is these diseases which will eventually kill a person infected with HIV/AIDS rather than the virus itself. • Transmission of HIV occurs in a number of ways. It can be carried in many bodily fluids (blood, semen, breast milk and vaginal fluid) and is transmitted through any method of unprotected sexual intercourse, blood transfusions, sharing of needles, mother-to-baby infection during pregnancy, breastfeeding, childbirth, or any other exposure to these fluids, including blood-to-blood contact. |
| Describe the global impact of HIV/AIDS. | • HIV/AIDS is a worldwide problem, with over 40 million people living with HIV worldwide, and more than half of those being from sub-Saharan Africa. |
| Describe the means of transmission of TB. | • Tuberculosis (or TB) is caused either by the bacterium Mycobacterium tuberculosis or M. bovis. • TB can infect many parts of the body, it is usually found in the lungs. • It is believed that TB infects as much as 30% of the world’s population, being inactive (or at least controlled by the immune system) in most people. • It is spread by droplet infection, i.e. by sneezing and coughing which expels hundreds of droplets containing the bacteria. • Conditions which make the spread of tuberculosis more likely include overcrowding in a house, poor ventilation, poor diet, homelessness and living or working with people who have migrated from areas of high TB-concentration. • The disease can also be contracted from cattle milk and meat, although this has been largely, if not totally eradicated in the developed world, but still remains a common problem in the underdeveloped world. |
| Describe the global impact of TB. | • TB is, like HIV/AIDS a worldwide problem. • Approximately 1% of the world’s population becoming exposed to and infected with the disease, and around 10% to 15% of those people go on to develop the disease (0.1-0.15% of the total population). • The disease is most common in south-eastern Asia and sub-Saharan Africa. • The numbers of infected people from TB have been increasing each year now for decades, and the WHO declared it a public health emergency in 1993 as different strains become resistant to the drugs used. |
| What is meant by the term ' Direct transmission' ? | |
| Give a few examples |
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