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Transcript
The Immune System Nonspecific and Specific Defense You do not need to write down anything in blue. What is a pathogen? • Pathogen: disease causing agent • Harmful to living things Check out this slow motion sneeze! http://www.youtube .com/watch?v=e2QA GVMlns4 Examples of Pathogens include • Bacteria • Viruses • Parasites, like fungi, protists, & worms How are Pathogens Spread? • Soil • Water • Infected animals • Food • Animal Bites – This includes mosquitoes (West Nile Virus), ticks (Lyme Disease), fleas (Bubonic plague), flies (various infections) • Person-to-person contact Q: How do bacteria cause damage to host cells? A: By releasing poisonous substances called toxins. • Did you know?…the Tetanus bacteria is found in soil and one drop of the toxin, the size of a period, can kill 30 people. These images are of two men undergoing an extreme muscle spasm caused by toxins produced by tetanus bacteria. The Immune System Immune System: body system that fights off invading pathogens Two types of defense: • Nonspecific Defense • Specific Defense st 1 line of Non-Specific Defense Skin: A physical barrier to pathogens. • Any break in the skin allows entry. • Releases sweat, oils, and waxes that contain chemicals toxic to bacteria. Mucous membranes: Tissues that line internal body surfaces that are in contact with the environment. • Mucous: Sticky fluid that traps pathogens. 1st line of Defense: Types of Non-specific Defense Stomach: Has acid that destroys potential pathogens that are swallowed Phagocytes: WBC’s that ingest (eat) pathogens • Macrophages: Ingest and Phagocytes and their relatives destroy pathogens. • Neutrophils: Ingest pathogens, then secrete deadly toxic chemicals to kill them • Short video clip on phagocytes: http://www.youtube.com/watch?v=CEOV-SFTlpY. Macrophage Neutrophils 1st line of Defense: Types of Non-specific Defense Moderate Fevers (< 103O F): Inhibit growth of pathogens and recruit macrophages Inflammation: Reaction to tissue damage. Phagocytes consume foreign substances. (Symptoms: swollen, redness, heat, pain) Inflammation Figure 24.2 Swelling Pin Skin surface Bacteria Phagocytes and fluid move into area Chemical signals Phagocytes WBC 1 Tissue injury; release of chemical signals such as histamine. 2 Dilation and increased leakiness of local blood vessels; migration of phagocytes to the area. 3 Phagocytes (macrophages and neutrophils) consume bacteria and cell debris; tissue heals. Specific Defense: The Immune System Organs of the Immune System: • Bone Marrow: makes WBC • Thymus gland: where T cells mature • Lymph nodes: contain lots of WBC • Spleen: removes pathogens from blood The Immune System involves many types of White Blood Cells (aka Leukocytes / WBCs). Here are a few types: B lymphocytes: Secrete antibodies. Antibodies: Y-shaped molecules that grab and block certain pathogens. T lymphocytes: Help stimulate an immune response. You can call them B cells and T cells for short! Specific Defense: Recognizing Pathogens Immune Response: your wbcs attack something Antigen: anything that causes a response Recognition: – Lymphocytes have receptor proteins all over them. – Receptor proteins recognize and bind to antigens that match the receptor. Immune Response gets stronger over time Immune Response: 1st time a certain pathogen is encountered by the body • After infection is fought, some B and T cells stay alive for years as memory cells. • Memory cells can divide to fight pathogens that they “remember” if they ever meet again. Primary Secondary Immune Response: a later exposure to the same pathogen • Response is faster and stronger due to memory cells. Draw this graph!