chapter 13: body defense mechanisms
Terms in this set (35)
Targets of the body's defense mechanisms
Pathogens (bacteria, viruses, protozoans, fungi, parasitic worms, prions) and cancer cells
Three strategies for defense
Keep the foreign organisms or molecules out of the body in the first place (chemical and physical surface barriers)
Attack any foreign organism or molecule or cancer cell in the body (internal cellular and chemical defenses)
Destroy a specific type of foreign organism or molecule or cancer inside the body (immune response)
First line of defense: Physical Barriers
Skin,nearly impenetrable; waterproof making it resistant to disruptive toxins and enzymes of invaders.
Mucous membranes line the digestive and respiratory passages, producing mucus that traps microbes preventing them from entering the body.
First line of defense: chemical barriers
tears: contain enzyme lysozyme that kills bacteria; washes away irritating bacteria and microbes
Saliva: washes microbes from teeth and mucous membranes of mouth
Sweat and oil from glands wash away microbes, and the acidity of the secretions slows bacteria growth
stomach lining: acid kills organisms
Second line of defense: defensive cells
Specialized scavenger cells called phagocytes engulf pathogens, dead cells, and damaged tissues. Neutrophils, macrophage. Eosinophils, WBCS (engulf pathogens too large for phagocytosis) Natural killer cells
Second line of defense: defensive proteins
Interferons: slow spread of virus
Complement system: protein that enhances the destruction of pathogens, enhances phagocytosis, and stimulates inflammation (makes blood vessels widen and become more permeable)
Second line of defense: inflammation
destroys invaders and helps repair and restore damaged tissue.
Signs are redness, heat, swelling, and pain
Second line of defense: fever
caused by pyrogens (bacterial toxin that resets the brains' internal thermostat to a higher temperature)
How complement proteins work
Activated complement protein form holes in the cell wall and membrane of the bacterium
The bacterium can no longer maintain a constant internal environment and water enters the cell
The bacterium bursts
Third line of defense: adaptive immune response
The body's specific defenses working together.
Characteristics of adaptive immune response
specificity: the adaptive immune response is directed at a particular pathogen
memory: remembers the pathogen and attacks it so quickly that illness doesn't result upon second exposure
molecules found on our own cells that label cells as "self" used by immune system to distinguish between what is part of your body and what is not
a non-self substance or organism that triggers an immune response such as proteins, polysaccharides, or nucleic acids, often found on the surface of an invader
responsible for the memory and specificity of the adaptive immune response, B and T cells
recognize specific MHC markers
T and B cells
when they recognize and antigen they divide repeatedly forming two lines of cells, effector and memory cells
short-lived cells that attack the invader, effector B cells use antibodies (y-shaped proteins) to neutralize the antigen.
long-lived cells that remember the invader and mount a quick response when it is next encountered.
Steps of adaptive immune response
a threat enters the body
Detection: a macrophage encounters, engulfs, and digests the invader. It places a piece of the invader on its surface creating an MHC marker
Alert: the macrophage presents the antigen to a helper T cell and secretes a chemical activating that helper T cell.
Alarm: the helper cell stimulates the B cell to begin dividing
Building specific defense: the B cell divides and forms plasma cells and memory cells
Defense: plasma cells secrete antibodies specific for that antigen
Continued Surveillance: memory B cells remain and mount a quick response when it is next encountered.
The cell mediated response
an effector cytotoxic T cell releases perforins which cause holes to form in cells with the particular antigen
occurs naturally whenever a person gets an infection, can also occur through vaccination when a harmless form of the antigen is introduced into the body to stimulate immune responses. It is long lived because memory cells are produced
results when a person receives antibodies produced by another person or animal. It is short lived because the recipient's body was not stimulated to produce memory cells
overreaction by the immune system to an antigen, the allergen is usually harmless, allergies are identified by injecting small amounts of the suspected antigens and monitoring skin response. Treatments are antihistamines to block histamine response
disease causing organisms including bacteria, viruses, protozoan, fungi, parasitic worms, and prions
prokaryotes that lack a nucleus and other membrane bound organelles, with a cell wall of peptidoglycan.
Produces enzymes that cause direct tissue damage and toxins that affect particular tissues
Three shapes of bacteria
Sphere (coccus) Rod (bacillus) Spiral (Spirilla)
How antibiotics inhibit growth of bacteria
prevent synthesis of cell walls
Block protein synthesis
when bacteria become resistant the antibiotics are no longer effective, caused by overuse and misuse of antibiotics
example is MRSA
responsible for many human illnesses
not considered living organisms, smaller than bacteria, made of genetic material surrounded by protein coat, some have envelpe studded with glycoproteins.
Steps in viral replication
Attachment: virus attaches to specific receptor on host cell
Penetration: all or part of the virus enters the host cell, in animals the entire virus enters the cell
Production of viral genetic info and proteins: virus directs structures in the host cell to make parts of new viruses
Assembly of new viruses: newly synthesized viral genetic information and proteins are used to form new viruses
Release: new viruses leave the cell, some leave by a process called budding or shedding.
Cancer causing viruses
insert cancer causing genes (oncogenes) into host cell chromosomes, disrupt functioning of host cell genes that regulate cell division
Viruses are difficult to destroy because its hard to kill it without killing the host cell
block a step in viral replication, best treatment is vaccination
Spread of disease
Direct contact (STDs) , indirect contact (inhalation such as respiratory illnesses) , contaminated food or water (hepatitis), animal vectors
three factors in the emergence or reemergence of disease
Development of new or drug-resistant organisms
Environmental changes that affect distribution of organisms
Population growth allows disease to spread more quickly and air travel allows disease to spread over greater distances
Factors that determine where new infectious diseases are likely to emerge
Rate of human population growth
Diversity of human population
Number of species of wild mammals