KEY CONCEPT Germs cause many diseases in humans. The first lines of defense against invading pathogens are the body’s nonspecific defenses (it doesn’t matter what is invading the body, the body will attack it)

Viruses, bacteria, viroids, and prions can all cause infection. 1 nanometer (nm) = one billionth of a meter 100 nm eukaryotics cells 10,000-100,000 nm viroids 5-150 nm viruses 50-200 nm prokaryotics cells 200-10,000 nm prion 2-10 nm 2

Fungi, protists, invertebrates also cause infection

Different pathogens cause common infectious diseases.

Pathogens can enter the body in different ways. person-to person contact breathing in infected air animal bite contaminated water contaminated food

Many body systems protect you from pathogens. Many other tissues and systems help the immune system. Skin is a physical barrier to infection. It releases sweat, oils, and waxes. Mucous membranes trap pathogens entering the body. Secretes mucus (sticky fluid that traps pathogens)

Many body systems work to produce nonspecific responses. Nonspecific responses are the same for every pathogen. In inflammation, blood vessels become leaky. white blood cells move toward infection and damaged tissue capillary wall extracellular space white blood cell characterized by swelling, redness, and pain includes chemical messengers such as histamines (increase blood flow to area)

The Inflammatory Response occurs If blood vessels are damaged – platelets & proteins clot the blood Chemicals releases, attract white blood cells to engulf pathogens platelets fibrin white blood cell red blood cell blood vessel clot

Fever – sign that the body is fighting an infection. In fever, body temperature increases. Low fevers stimulate white blood cells to mature. High fevers can cause seizure, brain damage, and even death.

Organs of the immune system Bone marrow – soft material found inside long bones Makes red & white blood cells & platelets Thymus – behind heart - WBC’s mature here; develop ability to recognize specific pathogens Lymph Nodes – found in neck, arm pit, groin (“swollen glands”) - Filter pathogens from lymph (extra-cellular fluid), contain WBC’s Spleen – behind stomach - Filter & clean lymph of cell fragments and abnormal tissue, contain WBC’s

Cells and proteins fight the body’s infections. White blood cells attack infections inside the body. Phagocytes engulf and destroy pathogens. T cells destroy infected cells. B cells produce antibodies.

Cells of the immune system produce specific responses. Specific immune responses begin with the detection of antigens. Antigens are surface proteins on pathogens. Each pathogen has a different antigen. virus antigens

Immunity Being resistant to a specific pathogen Active immunity: Being infected and survive vaccination Passive immunity occurs without an immune response: 1. mother’s milk 2. Genetics 3. Blood transfusion

Allergies occur when the immune system responds to harmless antigens. An allergy is an response to a harmless antigen. Allergies are caused by allergens. Allergens are antigens that cause an allergic reaction. Allergens cause inflammation responses. (allergy symptoms)

There are many different allergens. food, e.g. peanuts, milk, wheat, etc. airborne, e.g. pollen, dust mite feces, mold, etc. chemical, e.g. nickel, medicine, bee stings, etc.

Allergens can cause anaphylaxis. Anaphylaxis is an extreme inflammation response. Blood vessels and airways become too porous. If not treated immediately, anaphylaxis can cause death.

In autoimmune diseases, white blood cells attack the body’s healthy cells. Autoimmune diseases are failures of the immune system. White blood cells cannot recognize healthy cells. White blood cells attack healthy body cells. Tissues fail because of attack.

There are over 60 autoimmune diseases.