Ch. 18 Fighting Disease Section 1: Infectious Disease

Infectious Diseases A disease that is caused by the presence of a living thing within the body. They are a result of pathogens getting into your body and causing harm. Pathogens are organisms that cause disease. They make you sick by damaging individual cells. (ex. Strep throat attacks your cells in your throat)

Joseph Lister British surgeon in the 1860s. Hypothesized that microorganisms caused diseases. He began to wash his hands and clean his instruments. As a result the risk of infection decreased drastically.

Louis Pasteur A French Scientist in the 1860s Showed that certain organisms caused certain diseases. He showed that by killing the microorganisms could prevent the spread of that disease.

Robert Koch German physician in the 1870s and 1880s Demonstrated that specific pathogens caused certain diseases.

Kinds of Pathogens Bacteria, Viruses, Protist, Fungi Bacteria- ear infections, strep throat, food poisoning. Viruses- colds and flu Protist- Malaria, Amebic dysentery Fungi- athletes foot and ring worm

How Pathogens are spread Pathogens can spread through contact with either an infected person, soil, food, or water, a contaminated object or animal. Some can contaminate food or water. (dysentery)

How are Pathogens Spread Some pathogens can survive outside of the body. (cold and flu) You can be infected by touching contaminated objects. You can also catch diseases from infected animals. If you are bitten by a Deer Tick that is carrying Lyme Disease then you can catch that disease.

Questions 1.What is a Pathogen? 2.How do Pathogens cause infectious diseases? 3.How did Pasteur and Koch contribute to the understanding of the causes of infectious diseases? 4.What are 4 ways pathogens can infect humans?

Ch. 18, Section 2 The Body’s Defenses

Barriers that keep pathogens out Skin, Breathing passages, mouth and stomach Skin doesn’t let most pathogens in. A cut however can allow pathogens to enter the body. Pathogens can enter through nose and mouth when you are breathing. Mucus and cilia trap and remove most pathogens.

Inflammatory Response The body’s second line of defense. It responds the same to all pathogens. Fluid and white blood cells leak from blood vessels into nearby tissues. The white blood cells then fight the pathogens. A phagocyte is a white blood cell that engulfs pathogens and destroys them by breaking them down. What type of white blood cells are apart of the inflammatory response?

The Immune System Immune response is the body’s third line of defense. Triggers when a pathogen causes a fever. T-cell- identifies pathogens and distinguish one kind of pathogen from another. Antigen- molecules that the immune system either recognizes either as part of your body or as coming from outside your body.

T-Cell

Immune System B-cell- produce proteins that help destroy pathogens. These are called antibodies. Antibodies: proteins that help destroy pathogens. Antibodies destroy pathogens by binding to antigens on a pathogen.

AIDS AIDS- Acquired immunodeficiency syndrome is caused by HIV (Human immunodeficiency virus) HIV attacks the immune system and destroys T- cells. Eventually the body is unable to fight off diseases. There is no cure for AIDS, there are medicines that allow people to live much longer than those in the past.

Section 3, Preventing Infectious Diseases Active Immunity- the body has produced antibodies that fight a certain disease. Ex. You only catch the Chicken Pox Virus once. A person acquires active immunity when their own immune system produces antibodies in response to the presence of a pathogen.

Immune Response 1 st way to gain active immunity Memory cells in your body recognize antigens and then your body is able to fight off the pathogen before you get sick.

Vaccination 2 nd way to gain active immunity Harmless antigens are introduced to a persons body to produce active immunity. Given by injections, mouth, or a nasal spray. This allows your body to produce memory cells. Vaccines are made from weakened or dead pathogens. You usually do not get sick from vaccines.

When you do get sick Antibiotics are used to fight off bacterial infections. It is a chemical that kills bacteria or slows their growth without harming body cells. They do not kill viral diseases. When you are sick you should get plenty of rest, drink fluids, and eat a well balanced meal.

Passive Immunity Antibodies are given to a person, the person’s immune system does not make them. So they are coming from an outside source. Rabies is a very uncommon disease that people do not receive vaccinations for. If a person has rabies they have to inject the antibodies into them to fight off the disease.