31.2 Immune System. KEY CONCEPT. Germs cause ... Skin is (the first) a physical barrier to infection. â Mucous membranes trap pathogens entering the...
31.2 Immune System KEY CONCEPT Germs cause many diseases in humans.
31.2 Immune System Germ theory states that microscopic particles cause certain diseases.
• Germ theory proposes that microorganisms cause diseases (not spirits, as once believed). – proposed by Louis Pasteur – led to rapid advances in understanding disease
31.2 Immune System • Supported by Koch’s postulates. • Disease-causing agents, or particles, are called pathogens.
31.2 Immune System There are different types of pathogens.
• Bacteria are single-celled organisms. – cause illness by destroying cells – release toxic chemicals – Ex: food poisoning • Viruses are genetic material surrounded by a protein coat. – force host cells to make more viruses – very small – Ex: flu, cold, AIDS
31.2 Immune System • Fungi can be multicellular or single-celled. – take nutrients from host cells by piercing healthy cells – occur in warm and damp places – Ex. Athlete’s foot • Protozoa are single-celled organisms. – use host cells to complete their life cycles – take nutrients from host cell – Ex. Malaria
31.2 Immune System • Parasites are multicellular organisms. – grow and feed on a host – possibly kill the host
31.2 Immune System • Different pathogen cause common infectious diseases.
31.2 Immune System Pathogens can enter the body in different ways.
• Pathogens can be transferred by indirect or direct contact. • Indirect contact does not require touching an infected individual. – touching an infected surface – breathing in infected air –vectors (carry a pathogen and transmit into healthy cell) –ex: insects or food
31.2 Immune System • Direct contact requires touching an infected individual. Includes: – kissing – sexual intercourse – hand shaking
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31.2 Immune System KEY CONCEPT The immune systems consists of organs, cells, and molecules that fight infections.
31.2 Immune System Many body systems protect you from pathogens.
• The immune system is the body system that fights off infection and pathogens. • Many other tissues and systems help the immune system. – Skin is (the first) a physical barrier to infection. – Mucous membranes trap pathogens entering the body. – The circulatory system transports immune cells.
31.2 Immune System 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, which deactivate the pathogen.
31.2 Immune System
31.2 Immune System • Three types of proteins fight off invading pathogens. – Complement proteins weaken pathogen membranes. – Antibodies make pathogens ineffective. – Interferons prevent viruses from infecting healthy cells. antibody
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31.2 Immune System Immunity prevents a person from getting sick from a pathogen.
• In all types of immunity, pathogens are destroyed before you get sick. • Passive immunity occurs without an immune response. – mother’s milk – Genetics • Active immunity occurs after a specific immune response.
31.2 Immune System Vaccines artificially produce acquired immunity. • Vaccines control pathogens and disease – Injected with antibodies that have been exposed to the pathogen. - Gives instant but short- term protection.
– Given mild or dead version of the pathogen. - Your body makes the antigens itself for long-term protection. - Memory B cells stay for a long time, ready for another attack from the same organism.