Basic Body Systems Unit 6 Immune System Lecture Pages and Chapter 5 and 17

Viruses A virus is technically not alive because it doesn’t have any organelles inside it It also cannot live on its own, it has to have a host A virus that infects bacteria is called a bacteriophage

Virus Structure A virus is a piece of nucleic acid covered by an outer coat of protein called a capsid

Reproduction in Viruses Viruses reproduce themselves inside of their host The tail fibers of the virus attach the outside of a cell Enzymes from the virus make a hole in the cell and inject the virus’ genetic material inside Once inside of the host, the virus controls the cell and reproduces itself

Eventually there are so many new viruses made that the host membrane ruptures All the viruses escape to attack new cells Usually the host cell dies at this point Some viruses, like HIV, don’t kill the host as the new viruses are released

Dormant or Active Some viruses can live in your cells and go dormant, or sleep Cold sores are causes by viruses that live in your body When they are active you will see the sore

Classifying Viruses Viruses are classified based on which type of organisms they infect There are plant viruses, animal, and bacteria viruses Three ways viruses are classified: 1. Structure of the capsid 2. Does it contain DNA or RNA? 3. The way it reproduces

Defense Systems Pathogens are agents that cause diseases in your body Your body is constantly fighting them off

Skin Skin is made of layers of cells that block the entry of most pathogens This is your body’s first line of defense

Digestive System Bacteria and viruses enter the body through your mouth Hydrochloric acid in your stomach helps kill them

Respiratory System Bacteria and viruses can enter your body through your nose Hair and mucous help trap them as you breathe in Your body gets rid of them when you sneeze and cough

Circulatory System White blood cells called phagocytes travel in your bloodstream and attack bacteria and viruses it meets The white blood cell eats them

The Lymphatic System White blood cells called lymphocytes hang out in the tonsils, spleen, and various glands and fight bacteria and viruses

The Immune System White blood cells called B and T cells send signals to the immune system that a foreign substance is present called antigens The immune system makes antibodies that fight off these specific antigens

Resisting Disease Once the body has made specific antibodies, they remain so the next time they are ready when needed When you have these antibodies, your are immune to that disease

Types of Immunity There are two types of immunity: 1. natural 2. acquired

Natural Immunity Natural immunity means you are born with certain antibodies

Active Acquired Immunity Your body fights a disease because it has had it once already and made the specific antibodies to fight it Ex: chicken pox

T cells and B cells T cells work by calling the B cells into action T cells determine what antibody is needed, and B cells help the phagocytes attack

Passive Acquired Immunity Instead of making the antibodies, your body gets them from somewhere else Example: the flu shot This type of immunity does not last as long

Vaccines Vaccines are a serum injected into the body that help it make antibodies to fight a specific disease Ex: polio, measles, mumps

Germ Theory Diseases are caused by microscopic organisms called germs

Identifying Germs Cholera affects the small intestine Lyme disease affects the skin, joints, heart Salmonella affects the intestine Tetanus affects the nerves Tuberculosis affects the lungs, bone, and organs

Spread of Bacterial Diseases Most diseases caused by bacteria are contagious This means they can be spread from one person to another Some diseases are spread by living organisms

Treating Disease Medicine and injections Antibiotics kill bacteria

Discovery of Antibiotics Penicillin, a type of mold, was the first developed antibiotic Today they are produced from plants, animals, bacteria, etc

How Antibiotics Work Antibiotics are made for a specific disease Allergic reactions can happen

Overuse of Antibiotics Antibiotics can kill both the harmful and the useful bacteria in your body Bacteria can also become resistant to the antibiotic and no longer work

Viral Diseases Different kinds of viruses attack different parts of the body Viruses that cause warts only attack skin cells

Common Viral Diseases The common cold and the flu are both caused by viruses Others include chicken pox, measles, mumps, and hepatitis

HIV Human immunodeficiency virus (HIV) attacks a persons immune system Causes acquired immune deficiency syndrome (AIDS) AIDS kills white blood cells so you can’t fight off diseases

Transmission of AIDS In order to get aids you must exchange blood or body fluids from an infected person This can happen during sexual contact This can happen during a blood transfusion