Chapter 40 The Immune System & Disease Section 40-1 Infectious Diseases

Disease Any change, other than an injury, that disrupts the normal functions of the body Produced by: 1. bacteria 2. viruses 3. fungi 4. materials in the environment 5. inherited traits Pathogens – disease causing agents Diseases caused by pathogens are generally called “Infectious Diseases”

Germ Theory of Disease Scientists Pasteur & Koch concluded that infectious diseases were caused by microoganisms of different types, commonly called GERMS. Koch developed a series of rules still used today to identify microorganisms that causes a specific disease, called Koch’s Postulates

Koch’s Postulates Turn to page 1032 & copy the 4 main rules Identifying pathogens that cause disease is the first step toward preventing or curing the sicknesses they produce

Agents of Disease The human body provides just the right condition for the growth of many pathogens (right temp, watery environment, & lots of nutrients) Some pathogens (viruses/bacteria) destroy cells as they grow Bacteria release toxins that harm the body Parasitic worms removes nutrients & cause body functions to shut down

Viruses Tiny particles that invade & replicate within living cells Attach to cell, insert DNA/RNA into nucleus and take over the cell’s functions Can infect every type of organism Colds, flu, smallpox, chicken pox, herpes, HIV No cure

Bacteria Most are harmless to humans Few are deadly Cause disease 2 ways: 1. break down tissue in infected organism for food 2. release toxins that harm body Ear infections, strep throat, anthrax

Protists Small parasites that live on insects, animals, plants and contaminated water Cause the single most damaging infectious disease – MALARIA

Worms Flatworms & roundworms are responsible for many human diseases Usually are found in contaminated water or living on other organisms Tapeworm, ringworm & hookworms are examples

Fungi Most are harmless to human Athlete’s Foot – cause by Tinea, that penetrates the outer layers of the skin Can infect the nails, mouth & throat

How Diseases are Spread From 1 person to another through coughing, or PHYSICAL CONTACT Through contaminated water or food Spread through infected animals

Direct Physical Contact Through touching a person who is infected Through sexual contact – this includes kissing !!!!

Indirect Physical Contact Carried through the air – coughs & sneezes Touching an object that has pathogens on it Can be prevented: 1. cover mouth when coughing/sneezing 2. washing hands

Contaminated Food & Water Food poisoning is caused by eating food that contains pathogens Bacteria is always present in uncooked meat Bacteria grow rapidly in warm, partially cooked food Contaminated water causes disease, especially in areas with poor sanitation & untreated sewage

Infected Animals Animals also spread disease Animals that carry pathogens from person to person are called VECTORS Malaria, Lyme disease, West Nile Virus, rabies are diseases carried by vectors

Fighting Infectious Diseases Prevention isn’t always possible Some medicines have been developed to fight pathogens Antibiotics – compounds that kill bacteria without harming the cells of the organism Antibiotics have no effect on viruses, only bacteria Antiviral medicines – stop the ability of viruses to invade the cells

Over the Counter Medicines Treat only the symptoms of the disease Help you feel better – but does not treat the cause of the infection Best treatment – rest, well-balanced diet, & plenty of fluids

Section 40-2 Immune System A series of defenses that guard your body against disease Recognizes, attacks, destroys, & “remembers” each type of pathogen that enters the body Produces specialized cells that inactivate the pathogen Function: to fight infection by producing cells that inactivate foreign substances or cells This is called IMMUNITY

Nonspecific Defenses The fortress walls around the body Do not discriminate between 1 threat and another (reacts the same no matter what) Include physical & chemical barriers 1st Line of Defense: 1. Most important – SKIN 2. mucus, saliva, tears, oil & sweat glands 2nd Line of Defense: inflammatory response

Skin Very few pathogens can get across the layers of dead cells on the surface When broken (cuts or wounds), pathogens enter very easily & multiply Causes symptoms of INFECTION: 1. swelling 2. redness 3. pain 4. heat

Secretions of the Body Mucus, saliva and tears - all contain LYSOZYME – breaks down the cell walls of bacteria Oil & sweat glands produce an acidic environment on the skin that kills many bacteria Mucus in mouth & nose help trap pathogens Stomach acids & digestive enzymes destroy many pathogens that get in your stomach

Inflammatory Response A nonspecific defense reaction to tissue damage caused by injury or infection Millions of white blood cells are produced – which fight the infection Blood vessels near the wound expand, allowing the WBCs to travel faster to infected tissue WBCs engulf & destroy bacteria Area becomes swollen & painful Body release chemicals to increase body temp. – fever – slows or stops the growth of the pathogen Fever also causes heart rate to increase which pushes WBCs to infected tissue faster

Interferons Proteins that help other cells resist viral infections Interfere with the growth of the virus Slows down the progress of the infection & gives the immune system time to respond

Specific Defenses If a pathogen gets through the nonspecific defenses, the body STARTS the IMMUNE RESPONSE ANTIGENS: substances that trigger this response – viruses, bacteria Cells in the immune system can recognize these antigens are called - lymphocytes

Lymphoctyes B Cells – provide immunity against antigens & pathogens in body fluids - this is called HUMORAL IMMUNITY T-cells – provide defense against abnormal cells & pathogens inside living cells. - this is called CELL-MEDIATED IMMUNITY

Humoral Immunity When a pathogen enters the body, it is recognized by a small amount of B cells These B cells grow & divide rapidly – producing many memory B cells & Plasma cells

Plasma cells Plasma cells release ANTIBODIES – recognize & bind to antigens Antibodies attack the pathogen until it has taken it over Once infection is gone, the plasma cells die & stop producing antibodies

Memory B Cells Remember every pathogen that enters the body Able to produce antibodies if exposed again Greatly reduces the chance of being infected again

Antibody Structure Shaped like a Y and has 2 binding sites to connect with antigens The different shapes give antibodies the ability to recognize a large variety of antigens Its estimated that a healthy adult can produce about 100 million different types of antibodies

Cell-Mediated Immunity The body’s primary defense against its own cells when they have become cancerous or infected by viruses Also important in fighting infection by fungi & protists Viruses & other pathogens can not be destroyed by antibodies alone

Process of cell mediated immunity T cells divide & change into Killer T cells, Helper T cells, & Memory T cells Killer T cells find & destroy the pathogen or foreign tissue that contains the antigen Helper T cells produce Memory T cells Memory T cells remember the antigen in case of future invasion Once pathogen is taken over, Suppressor T cells shut down Killer T cells

Acquired Immunity when immunity is taken from outside the body – not naturally made Two types Active Immunity Passive Immunity

Active Immunity Vaccination – injection of a weakened form of a pathogen to produce immunity More than 20 serious human diseases can be prevented by vaccinations Modern vaccines stimulate the immune system to create millions of plasma cells ready to produce specific types of antibodies When the body reacts to the vaccines it is known as Active Immunity

Passive Immunity When antibodies produced by other animals against a pathogen are injected into the bloodstream Last only a short time Can develop naturally - passing from mother to child through placenta or breast feeing or by deliberate exposure - vaccines for malaria or when someone is bitten from snake or rodent