Transcript Copy everything in RED Disease = any change, other than injury, that disrupts the normal functions of the body  Diseases can.

Copy everything in RED
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
Section 40-1
Pathogen
Types
Viruses
Bacteria
Protists
Worms
Fungi
Chicken pox
Agent That Causes
Disease
Rhinovirus
Two types (A, B),
plus subtypes
Varicella
Measles
Paramyxovirus
Tuberculosis
Mycobacterium
tuberculosis
Neisseria meningitidis
Vibrio cholerae
Clostridium tetani
Trypanosoma
Disease
Common cold
Influenza
Meningitis
Cholera
Tetanus
African sleeping
sickness
Malaria
Amoebic dysentery
Schistosomiasis
Beef tapeworm
Athlete’s foot
Ringworm
Plasmodium
Entamoeba histolytica
Schistosoma
Taenia saginata
Imperfect fungi
Imperfect fungi
Method of
Transmission
Airborne; direct contact with infected person
Airborne; droplet infection; direct contact with
infected person
Airborne; direct contact with infected person
Droplets in air; direct contact with secretions of
infected person
Droplets in air; contaminated milk and dairy products
Direct contact with a carrier
Contaminated drinking water
Contaminated wound; usually puncture wound
Spread by tsetse fly
Spread by Anopheles mosquitoes
Contaminated drinking water
Freshwater streams and rice paddies
Contaminated meat
Contact with infected person
Exchange of hats, combs, or athletic head gear with
infected person
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
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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.
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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
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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
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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)
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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