Disease = any change, other than injury, that disrupts the normal functions of the body Diseases...
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Transcript of Disease = any change, other than injury, that disrupts the normal functions of the body Diseases...
Disease = any change, other than injury, that disrupts the normal functions of the body Diseases can be inherited (ex. Hemophilia) Diseases can be caused by materials in the
environment (ex. Cigarette smoke) Diseases can be produced by agents (ex.
Bacteria, viruses, fungi) = pathogens Pathogens = “sickness-makers” Diseases caused by pathogens = infectious
diseases, because they enter, or infect, the body
The human body provides great conditions for pathogenic growth
You have many different microorganisms living in your body that are actually harmless or beneficial
However, some microorganisms are dangerous Some bacteria break down body tissues and
others release toxins (poisons) Some protists, fungi, and worms are parasites
that live inside you and use up your nutrients or destroy blood/nerve cells
Viruses are nonliving pathogens that use a host cell to make copies of the virus and destroy other cells
Infectious diseases are spread From person to person: coughing, sneezing, or
physical contact▪ Common cold, mumps, measles, influenza,
STDs (AIDS), meningitis, athlete’s foot Contaminated water and/or food
▪ Cholera, dysentery, E.coli infection, salmonellosis
Vectors: infected animals (ticks/mosquitoes)▪ Lyme disease, malaria, West Nile virus, rabies
Viruses
Protists
Worms
Fungi
Disease Agent That Causes Disease
Method of Transmission
Common coldInfluenza
Chicken pox
Measles
Tuberculosis
Meningitis
CholeraTetanusAfrican sleeping sicknessMalariaAmoebic dysenterySchistosomiasisBeef tapeworm
Athlete’s foot
Ringworm
RhinovirusTwo types (A, B), plus subtypesVaricella
Paramyxovirus
Mycobacterium tuberculosisNeisseria meningitidisVibrio choleraeClostridium tetaniTrypanosoma
PlasmodiumEntamoeba histolyticaSchistosomaTaenia saginata
Imperfect fungi
Imperfect fungi
Airborne; direct contact with infected personAirborne; droplet infection; direct contact with infected personAirborne; direct contact with infected personDroplets in air; direct contact with secretions of infected personDroplets in air; contaminated milk and dairy products
Direct contact with a carrier
Contaminated drinking waterContaminated wound; usually puncture wound
Spread by tsetse fly
Spread by Anopheles mosquitoes
Contaminated drinking waterFreshwater streams and rice paddies Contaminated meat
Contact with infected personExchange of hats, combs, or athletic head gear with infected person
Section 40-1
Pathogen Types
Bacteria
Drugs have been developed to use against pathogens
Antibiotics = chemicals that kill bacteria without harming the cells of humans or animals Penicillin = interferes with the synthesis of
cells walls by Eubacteria (breaks down peptidoglycan in their cell walls))
Streptomycin = interferes with bacterial growth by blocking protein synthesis in ribosomes
Antivirals = inhibit the ability of viruses to invade cells or multiply inside cells
A series of defenses that guard against diseases = body’s protection
Nonspecific defenses = “walls” of the immune system keeping everything out
Specific defenses = “security guards” identifying and inhibiting pathogens
Skin = most important nonspecific defense Physical barrier Acidic environment on surface kills bacteria
Mucus, sweat, tears and saliva Traps pathogens and removes them from the body by cilia or destroys
them using the enzyme lysozyme, which breaks down cell walls Inflammatory response = reaction to tissue
damage caused by injury or infection Blood vessels around wound expand, white blood cells enter infected
tissue and phagocytes (special WBCs) engulf and destroy bacteria, tissue becomes swollen and painful, body temperature ingrowth and increase circulation and activity of WBCs
Interferon = proteins that “interfere” with the virus creases (fever) to slow pathogen Proteins released by virus-infected
cells to help other cells resist viral infection by inhibiting viral protein synthesis, blocking viral replication
Pathogen: any disease causing agent
Antigen = a substance that triggers the immune response (organic molecules on the surface of pathogens) Antigens are chemicals
present on the surface of viruses, bacteria, pollen grains etc.
Antibody = protein that helps destroy pathogens by binding to antigen and attracting phagocytes to engulf and destroy them
Immunity against pathogens in the body fluids (blood/lymph)
Immunity produced by lymphocytes (type of WBC)
B lymphocytes (B cells) produce antibodies to mark pathogens and prevent future infections
Immunity that relies on lymphocytes (cells) Killer T cells (cytotoxic T cells) can attack
infected cells and destroy their cell membranes Killer T cells are what make organ transplants
difficult, because they see the new organ as foreign and begin to attack it = rejection.
People that survived infectious diseases, never developed the same disease again
Memory B and T cells remain capable of producing specific antibodies to that pathogen, ensuring the disease never gets a chance to develop again
An immediate active immune response against the pathogen in a vaccine
Vaccination = injection of a weakened or mild form of a pathogen to produce immunity Prevents serious human diseases by
stimulating the immune system to create plasma cells capable of producing the specific antibodies for another possible infection
Active Immunity lasts long term (permanent)
Antibodies produced by other animals for a pathogen are injected into the bloodstream The antibodies will produce passive
immunity against a pathogen as long as they remain in circulation (several weeks)
Antibodies from the mother are passed to the fetus through the placenta or to the infant in the mother’s milk = maternal immunity The antibodies will produce passive
immunity against most infectious diseases for the first few months of life or longer if breast-fed
Although the immune system defends the body from potential pathogens, sometimes disorders occur The immune system may overreact
to an antigen, producing discomfort or disease
The cellular nature of the immune response is a potential weak point
Overreaction of the immune system Allergies occur when antigens from allergens
(pollen, dust, dust mites) bind to mast cells (type of immune cell common in nasal passages)
Activated mast cells release chemicals = histamines, which increase the flow of blood and fluids to the surrounding area (sneezing, runny eyes/nose, etc)
Antihistamines = drugs used to reduce allergy symptoms by counteracting the effects of histamines
Asthma = allergic reaction where smooth muscle contractions reduce the size of air passageways in the lungs making breathing difficult
The immune system has the ability to distinguish “self” from “nonself”
The immune system makes a mistake and attacks the body’s own cells (“it attacks itself”) Juvenile-onset diabetes (immune system attacks
insulin-producing cells in pancreas) Myasthenia gravis (attacks neuromuscular
junctions) Multiple Sclerosis (destruction of myelin sheath –
attacks nervous system) Lupus (attacks cells and tissues resulting in
inflammation and tissue damage: heart, joints, skin, lungs, blood vessels, liver, kidneys and nervous system)
Acquired Immune Deficiency Syndrome (AIDS) = when cells of the immune system are weakened by infection
Caused by HIV (human immunodeficiency virus) and spread by contact with body fluids (drug needles, unprotected sexual intercourse, breast milk, blood during birth, blood transfusions)
HIV attaches and destroys most helper T cells, so body is more susceptible to infections
People DO NOT die from HIV/AIDS, they die from the infections they get because the HIV virus has left their immune system unable to respond to the infections
Cancer is caused by defects in the genes that regulate cell growth and division Inherited genes Viruses: interfere with cell cycle (mitosis)
▪ Ex. Human papilloma virus (HPV: an STD) can lead to cervical cancer or genital warts (non cancerous)
Radiation: causes mutations in DNA▪ Ex. X-rays, nuclear radiation, sunlight (UV Rays)
Chemicals: cause mutations in DNA▪ Carcinogens = chemicals that cause cancer▪ Ex. Chloroform and benzene (industrial solvents used
in production of drugs, plastics and synthetic rubber, small component in gasoline), cigarette smoke