Infection and response

• Communicable diseases can be spread from person to person, such as measles.
• Non-communicable diseases cannot be passed from person to person, such as coronary heart disease.
• Diseases can be major causes of ill health, which is defined as the state of physical and mental well-being.
• Ill health can be caused by both communicable and non-communicable diseases, as well as poor diet, high levels of stress, and other life situations.
• Different types of diseases can interact, for example, a bacteria that causes tuberculosis can increase the risk of contracting another disease, such as cervical cancer, if the person has HPV.
• Allergies can be triggered by the immune system, for example, in cases of asthma or dermatitis, where the body is infected with a pathogen which the immune system fights off but then the person's left with an allergy.
• A mental illness can be triggered by a physical illness, for example, a person suffering from arthritis, a very painful joint condition, can find it difficult to move and lead a normal life, which can make them feel isolated and depressed.
• Pathogens are microorganisms that cause infectious disease.
• Pathogens include bacteria and viruses, which are the focus of this video.
• Pathogens also include protists and fungi, which will be discussed in later videos.
• Bacteria are a type of pathogen that cause food poisoning, with around 300,000 people in the UK getting food poisoning from this type of bacteria every year.
• Fortunately, most people recover from food poisoning, but sometimes it can be fatal.
• Many bacterial diseases can kill us.
• The key fact about bacteria is that once inside the human body, they reproduce very rapidly under ideal conditions, and can divide every 20 minutes.
• Bacteria can release harmful chemicals called toxins, which damage tissues and make us feel ill.
• Bacteria and viruses cause illness by invading the host cell and reproducing inside it, which is very damaging to the cell.
• In the case of highly infectious diseases such as Ebola, patients may be isolated to prevent the pathogen from spreading to other people.
• Another way of reducing the spread of pathogens is to use a condom during sexual intercourse, which reduces the spread of HIV.
• In the UK, drinking water contains chlorine which kills microorganisms.
• A pathogen is an organism that causes disease.
• Pathogens are usually spread in three ways: in the air, through water, and through contact between individuals.
• Practicing basic hygiene, providing clean drinking water, and reducing direct contact between individuals are ways to prevent the spread of pathogens.
• Vaccination is another way of reducing the spread of pathogens.
• Another type of pathogen that causes a lot of human diseases is viruses, with HIV being a virus that can lead to AIDS.
• Viruses are very different to bacteria because they cannot be produced by themselves and can only reproduce inside a host cell.
• Malaria is a common disease in certain parts of the world that causes over 400,000 deaths every year.
• Malaria is a communicable disease spread by a pathogen, and the malaria pathogen is an example of a protist.
• Malaria is a serious disease that causes repeated bouts of fever and can be fatal.
• The life cycle of the malaria pathogen involves a human being being bitten by a mosquito, the malaria pathogen passing into the mosquito, and the mosquito biting a different person.
• Scientists call the mosquito a vector because it carries a pathogen from one person to another person.
• There are two main ways to prevent the spread of malaria: stopping the vector, which is the mosquito from breeding, and preventing the mosquitoes from biting humans.
• One way to prevent the mosquitoes from biting humans is to sleep under a mosquito net.
• If the mosquito net is sprayed with insecticide, any mosquitoes that land on it are also killed.
• The job of the nonspecific defense system is to stop pathogens from entering the body.
• Sometimes, the nonspecific defense system doesn't work, for example, when the skin is damaged, allowing pathogens to invade the body and enter the bloodstream.
• The immune system, which also has two main functions, destroys pathogens and any toxins they produce, and protects us in case the same type of pathogen invade us again in the future.
• The immune system involves the white blood cells, which can ingest and destroy pathogens, detect chemicals released from the pathogen and move towards it, and use enzymes to destroy the pathogens in a process called phagocytosis.
• White blood cells can also destroy pathogens by making antibodies, which are protein molecules produced by white blood cells.
• Antibodies stick to the pathogens, triggering the pathogens to be destroyed.
• Antibodies are extremely specific, protecting against the specific pathogen they were developed against, but not against any other pathogen.