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Transcript
IMMUNE SYSTEM What causes disease? • Disease is: a disruption in a human body system that leads to corresponding disruption in homeostasis herpes • Diseases fall into two categories 1. Noninfectious 2. Infectious hemophilia Noninfectious Diseases • Diseases that cannot be transmitted from one organism to another • Examples – Genetic disorders, heart diseases, most cancers Infectious Diseases • Diseases that are contagious; can be transmitted from one organism to another • Examples – Chicken pox, HIV, cold, strep throat How are pathogens spread? 1. Air 2. Contaminated Objects/Infected Organisms 3. Contaminated Food/Water Salmonella enterica Bacteria diplo = double staphylo = a bunch of grapes/clusters strepto = are in chains • Most are harmless • Pathogenic bacteria cause disease – Can reproduce in their host and release toxins – Can produce enzymes that break down the host’s tissues Bacterial Diseases • Bacterial meningitis – Infection of the fluid surrounding the brain and spinal cord – Symptoms: high fever, headache, stiff neck – May lead to brain damage and hearing loss WHY? Stomach Ulcer • Sore/erosion of the lining of the stomach • Many are caused by Helicobacter pylori • Causes burning pain in the abdomen Peptic ulcer seen under endoscopy Helicobacter pylori seen under an electronic microscope Clostridium botulinum • botulism • when eaten - begins to reproduce and release a toxin that destroys the tips of nerve cells • paralysis may result Lyme Disease • Spread through insects • Caused by bacteria: Borrelia burgdorferi • Attacks the nervous system – Loss of memory – Muscle weakness/paralysis – Tingling/numbness in arms – Headaches Pathogen • Any foreign matter that enters the body that triggers and immune response – Virus – Bacteria – Prion Virus • segments of nucleic acids • smaller than bacteria • replicate by infecting susceptible cells and using them to reproduce more of the virus • nonliving (do not grow, perform homeostasis or metabolize) • covered by a protein coat which may contain RNA or DNA – RNA viruses: HIV, influenza, rabies – DNA viruses: warts, chickenpox, mononucleosis Replication of a virus • Lytic cycle: cycle of viral infection, replication and cell destruction • viral genes have entered a cell and use host cell to replicate these genes and make proteins • proteins are assembled to make new viruses • host cell is broken open and newly made viruses are released • Lysogenic cycle: viral genome replicates without destroying the host cell • viral gene inserts itself into the host chromosome (provirus) • whenever the cell divides, the virus also divides (resulting in two infected cells) • in some lysogenic viruses, a change in the environment can cause the provirus to enter into the lytic cycle • • • Viruses are often restricted to certain types of cells • flu attacks cells of the upper respiratory tract • HIV attacks white blood cells (body’s immune system cells) • Prions: infectious particles that are composed of proteins but NO nucleic acid (they cause infection by influencing how a protein folds into shape) • mad cow disease First Line of Defense (nonspecific) • Skin, sweat, & saliva – Contain chemicals that kill or inhibit some bacteria • Mucus – Covers internal membranes and traps pathogens • Stomach acid – Destroys pathogens in food Preventing Entry • Throat, mouth, and nose has mucus coatings – Trap foreign material – Skin protects our body a great amount Non Specific Immune Responses • Occurs when the body has become infected by a pathogen – Fever – Inflammation – Activation of specific proteins to kill the pathogen Fever • Normal temp 97.8-99 degrees farenheight • 103 can kill the pathogens • 105 can be fatal – Why can a fever this high be fatal? Inflammation • During an infection cells and chemicals that attack and destroy pathogens gather around • Histamines – Chemical – Blood vessels dialate- Increased blood flow causes swelling and redness Specific Immune Responses • Most pathogens are destroyed by the general immune responses – White blood cells target a particular invader • Macrophages – White blood cell – Destroys pathogens – Engulfs the pathogens Invader surface • Contain antigens on the surface of the cell – Composed of proteins • Every antigen has a corresponding antigen receptor on the surface of a white blood cell What else does this remind you of? Activation of the Immune System • A specific immune response is triggered by a helper t cell recognizing an invader • Helper t cells coordinate two responses. – Destroy infected cells – Clean up pathogens – Helper t cells have specific antigen receptors – Releases chemicals with allow other white blood cells to locate the pathogen Long-Term Protection • Preparation for future invasion my the same pathogen • Memory cells – Carry antigen receptors to the target antigen – Continues to circulate after the infection is over • Building an immunity Vaccine • Dead or weakened form of a virus • Do not trigger a general immune response • Causes the white blood cells to produce specific antibodies to the pathogen and causes memory cells to form Acne • Results when hair follicles become clogged with oil, dead skin cells and bacteria – whitehead: closed clogged up pore – blackhead: open, clogged pore – Pimples: small infection where bacteria entered • Bacteria produce toxins that attract WBCs • If a pimple bursts, there is an open wound (where more bacteria can enter) Viruses • Cannot reproduce on their own – Are they living? • Use a living organism to reproduce – Damages the host’s cells http://www.youtube.com/watch?v=chtTYBCvHa8 http://video.nationalgeographic.com/video/swine-flu- Bacteria • • • • • prokaryotes (lack nucleus) single cell circular DNA reproduce by binary fission flagella allows them to move (spins in a circle) • most have a cell wall Bacteria cause disease • Heterotrophic bacteria – obtain nutrients by secreting enzymes that break down complex organic structures and absorbing them • Tuberculosis: mycobacterium tuberculosis infects lung tissue and grows using the lungs nutrients – coughing up blood and sputum, chest pain, fever, fatigue, weight loss, loss of appetite • Bacteria can also secrete toxins (chemicals) Antibiotics • interfere with cellular process of bacteria (since these processes do not occur in viruses, they are ineffective against them) Immune Disorders • Allergy – Overreaction to an antigen that is not normally harmful • Histamine is released by infected cells causing inflammatory response • Autoimmune Diseases – Body fails to recognize some of it’s cells as “self” • Type I diabetes, multiple sclerosis, Graves disease Organ Transplant • Rejection – The body does not recognize the new organ as “self” and launches an attack against it • People who receive transplants are given immunosuppressants – Body may be more susceptible to infection - Rejection can still occur AIDS (Acquired Immune Deficiency Syndrome) • HIV (human immunodeficiency virus) – Infects helper T cells • Can remain dormant (not reproducing) for years – Active stage • Virus reproduces, spreads and destroys T cells • Weakened immune system • Symptoms of AIDS – Swollen lymph glands, fever, weakness, weight loss lytic cycle Viruses enter host 1. Virus’s genetic material enters the host cell 2. Virus uses host cell to reproduce its own genetic material and make proteins 3. Proteins are assembled with viral DNA to make new viruses 4. Host cell dies and breaks open, releasing new viruses Chicken Pox • caused by Varicella zoster • characterized by red, itchy spots • spreads through air (droplets) or through direct contact