Fighting Disease. enter body bacteria produce TOXINS which enter bloodstream and travel throughout body

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1 Pathogen: a disease-causing microorganism ex. parasites How Bacterial Pathogens Work Fighting Disease enter body bacteria produce TOXINS which enter bloodstream and travel throughout body WEBSITES Symptoms: chills, fever, etc. - harmful effects seen throughout body ex. step on rusty nail Clostridium tetani endospores enter body and begin to produce a NEUROTOXIN that causes the body to SPASM and lock; TETANUS - the body s muscles CONTRACT and stay that way - die from asphyxiation (cannot breathe) ex. Corynebacterium diphtheriae - toxin prevents cell organelles from producing proteins which causes the cell to malfunction DISEASES

2 Comparing Viral and Bacterial Diseases Viral diseases: organism takes over the host cell and alters its function so that the viral DNA or RNA is reproduced and new viruses are formed common cold - caused by airborne rhinovirus and others - transmitted by droplets from sneezing or coughing - symptoms include cough, congestion, mild fever - duration is about 1 week hepatitis B - caused by an enterovirus - transmitted in the exchange of body fluids - most people are initially asymptomatic, but symptoms will appear 1 3 months after infection; loss of appetite, fatigue, abdominal discomfort, nausea, and jaundice - long-term effects include liver cancer, cirrhosis of the liver, and acute chronic infection HIV/AIDS - caused by a retrovirus - transmitted in the exchange of body fluids - symptoms include the appearance of opportunistic diseases (rare diseases that only show up in people with weak immune systems) - 100% fatal, although treatments do exist that can prolong life for up to 15 years Bacterial diseases: organism produces toxins that affect cells and prevent them from functioning normally strep throat - caused by Streptococcus bacteria - transmitted by droplets from coughing or sneezing - symptoms include high fever, very sore throat - duration is 1 2 weeks; no long-lasting effects tetanus - caused by Clostridium tetani bacteria - transmitted through deep puncture wounds to the body: bacteria produce a neurotoxin that attacks neurons - symptoms include rigid muscle contractions, especially in the jaw (common name: lockjaw) - if not caught early, can result in paralysis or death botulism - caused by Clostridium botulinum bacteria - transmitted through improperly sterilized food that contains the bacterial spores - symptoms include blurred vision, difficulty swallowing and breathing, muscle weakness, nausea, vomiting - 1/3 of patients will die, all within a few days of initial symptoms

3 Symptoms: Disease in the body is recognized by symptoms. These symptoms include pain, swelling, infected wounds, poor digestion, stiff joints, weakened bones, or just general debilitation. Symptoms are not diseases in themselves but function as the body s early warning system. If we neglect these warnings, or worse, turn them off with drugs such as painkillers that suppress the symptoms, the disease remains. An analogy would be turning off a smoke detector because the sound is annoying. The result could be that the house burns down unless you find the cause of the smoke and extinguish it. If symptoms are ignored over a long period, it could be irreversible (smoker s cough _ lung cancer or emphysema). Fever occurs when white blood cells release endogenous pyrogens that work on the hypothalamus to raise body temperature. Most pathogenic viruses and bacteria can t thrive in hot environments. Some doctors suggest not taking fever reducers unless your temperature is very high (more than 39 C). Overview of the Body s Defences see book page 121 First Line of Defence (structural, non-specific) Skin: keeps organisms and allergens from entering the body sweat : contains salts and amino acids that are poisonous to bacteria Lysozyme: enzyme in tears, saliva, mucus secretions, perspiration; digests bacterial cell walls Cilia in respiratory passages: mucus helps trap inhaled bacteria and sweep up to throat Stomach acid: low ph kills pathogens Second Line of Defence (cellular, non-specific) White blood cells (leukocytes): Lymphocytes: found in the blood, tissue fluids, and lymph; produced in the bone marrow and thymus; produce antibodies Macrophages: produced in the bone marrow; engulf pathogens by phagocytosis; once the pathogens are inside the macrophage, it secretes lysozyme to kill the pathogens Pus: dead WBC and bacteria Lymphatic System: Complex network of organs connected by a special circulatory system of vessels and nodes - contains LYMPH: a transparent fluid containing lymphocytes Lymphatic organs and tissues: Tonsils: collections of lymph tissue in the back of the throat that filter out organisms that cause infection Thymus: organ in which new white blood cells develop specialized functions Liver: white blood cells in this organ remove organisms from the blood as it flows through Spleen: removes abnormal cells from circulation Mucous membranes in the respiratory and gastrointestinal tracts: contain immunoglobulins to destroy pathogens and allergens Lymph nodes: act as filters; produce antibodies to destroy invading organisms or abnormal cells Bone marrow: site of white blood cell formation

4 Third Line of Defence: Antibody Formation (specific) Undigested antigens stimulate the lymph nodes to produce memory cells and plasma cells. Plasma cells manufacture antibodies specifically shaped to deactivate the invaders. Antibodies circulate through the bloodstream and enter tissues to combat the remaining antigens. Macrophages consume and digest the deactivated antigen-antibody complex. Memory cells stored in lymph nodes remember how to produce identical antibodies if the same antigen invades again. Antibodies: good protein molecules that protect the body from invaders Antigen: bad a foreign material that causes formation of antibodies VERY SPECIFIC: one antibody per antigen Immunity 1. ACTIVE IMMUNITY: the body itself manufactures antibodies to combat a specific disease Acquired two ways: natural: person gets disease and body produces antibodies - this lasts a lifetime artificial: injection of a vaccine - the body recognizes this (vaccine contents) as ANTIGENS and produces ANTIBODIES to combat the intruders - some vaccines produce lifelong protection : diphtheria years: (boosters) small pox - one year: influenza VACCINES: dead or weakened pathogens (bacterial or viral) or other antigens 2. PASSIVE IMMUNITY: antibodies given to fight infection - temporary protection, no memory Acquired two ways: natural: mother passes on antibodies to baby before delivery or through breast milk (lasts a few months) - immunizations begin during the first year acquired: shot of antibody given to help fight antigen immediately ex. tetanus shot: an antidote to fight a possible infection of Clostridium tetani to prevent tetanus - the antidote or shot is derived from the plasma of an animal that has been exposed to this antigen - the protection lasts for 10 years

5 ACTIVE Types of active and passive immunity PASSIVE - body manufactures it own antibodies - antibodies are introduced into bloodstream NATURAL ARTIFICIAL NATURAL ACQUIRED through disease through vaccination through pregnancy and through vaccination contact and recovery breast-feeding e.g. tetanus Lifelong e.g., diphtheria Short-term Immunity e.g., influenza, smallpox Resisting Bacterial Infection Transmission: spreading the disease HOW: inhale dust or moisture droplets in air direct contact hand shake fecal contamination E.coli on hamburger animal bites insects are important VECTORS organisms that pass on pathogens wounds (cuts, scratches) ex. tetanus, flesh-eating bacteria PROTECTION: Sterilization: high temperatures destroy bacteria Disinfectants: chemicals that can kill microorganisms on surfaces - do not use on body Antiseptics: slows growth of microorganisms - can be used on body but not taken internally Burn: destroy all infected plant or animal material Antibacterial medication: ex. antibiotics like penicillin Antiseptics and disinfectants are both chemicals that destroy or impede the growth of disease-causing organisms. An antiseptic can be used on human skin without harming body cells; a disinfectant could harm human cells and is used on inanimate surfaces.

6 Autoimmune diseases: These are when the IMMUNE system ATTACKS a healthy body ex. multiple sclerosis, rheumatoid arthritis Multiple sclerosis is a chronic, inflammatory, autoimmune disease of the central nervous system (brain and spinal cord) that causes the destruction of the covering (myelin sheath) of the nerves. Plaques resulting from this inflammatory process that destroys normal, healthy myelin tissue are scattered throughout the central nervous system. These plaques block the ability of the nerves to transmit nervous system signals and can cause a wide range of neurological symptoms: loss of balance, impaired speech, extreme fatigue, double vision, and paralysis. The exact cause of MS is not known. Current belief is that MS results from an autoimmune response in someone genetically predisposed to develop an autoimmune disease, possibly triggered by a virus, chemical, or something in the person s environment. MS is the most common neurological disease affecting young adults in Canada, and Canadians have one of the highest rates of multiple sclerosis in the world. The disease can affect any age group. However, the diagnosis is most often made between 20 and 40 years of age, and women are twice as likely to develop MS as men. MS is more common in Caucasians than in those of African or Asian heritage.