31.1 KEY CONCEPT Germs cause many diseases in humans.
Germ Theory Germ theory proposes that microorganisms cause diseases. proposed by Louis Pasteur led to rapid advances in understanding disease
Disease-causing agents are called pathogens.
Pathogen Types Bacteria are single-celled organisms. cause illness by destroying cells release toxic chemicals
Viruses are genetic material surrounded by a protein coat. –force host cells to make more viruses –very small
Fungi can be multicellular or single-celled. –take nutrients from host cells –occur in warm and damp places
Protozoa are single-celled organisms. –use host cells to complete their life cycles –take nutrients from host cell –Ex: Malaria
Parasites are multicellular organisms. –grow and feed on a host –possibly kill the host
Vectors carry a pathogen and transmit it into healthy cells Direct contact requires touching an infected individual. kissing sexual intercourse hand shaking tick
31.2 KEY CONCEPT The immune systems consists of organs, cells, and molecules that fight infections.
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 a physical barrier to infection. Mucous membranes trap pathogens entering the body. The circulatory system transports immune cells.
Immune Cell Types White blood cells attack infections inside the body. Phagocytes engulf and destroy pathogens. T cells destroy infected cells. B cells produce antibodies.
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 pathogens
Immunity prevents a person from getting sick from a pathogen. In all 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