Topic 10 (immunity and diseases) Flashcards
What are the organisms that cause diseases in humans?
Organisms that cause diseases are called pathogens.
Transmissible diseases are diseases in which the pathogen can be passed from one host to another.
What is the external defense system?
Our bodies have natural defence mechanisms to prevent
pathogens from entering our bloodstream:
* Skin
* Hairs in the external nostrils
* Mucous membranes
* Stomach acid
How do pathogens get into our bodies?
Direct contact
a) Person-to-person contact
b) Exchange of body fluids
c) Breastfeeding (mother to infant)
Indirect contact
a) Contaminated surfaces
b) Airborne infection
c) Animals
How can the spread of waterborne and foodborne diseases be controlled?
(a) Having a clean water supply
(b) Having a proper waste disposal
(c) Having a proper sewage treatment
(d) Preparing food in a hygienic manner
(e) Practicing good personal hygiene
What is cholera?
Cholera is a disease caused by a bacterium that is transmitted
through contaminated food or water.
Treatment of cholera:
* Drink water containing some sugar and ions
* Intravenous fluid
* Antibiotics
Describe immunity and the immune system.
Immunity is the protection provided by the body’s defense system against a disease.
Specific immune system (or adaptive immune system)
When pathogens enter the bloodstream, they are destroyed by antibodies. Antibodies are proteins produced by lymphocytes. They are highly specific.
Each pathogen has its own distinct antigen. Only an antibody of a specific shape complementary to the antigen can bind to the antigen, forming an antibody-antigen complex.
Antibodies play an important role in destroying foreign particles.
Mention the two types of white blood cells and their functions.
*Phagocytes: Remove any microorganisms that invade the body and might cause infection by engulfing and digesting.
*Lymphocytes: Produce antibodies to fight antigens.
How does the immune system work?
*Antibodies bind to bacteria, making them ready for phagocytes to engulf and destroy.
*Antibodies bind to bacteria, causing them to clump together. This allows for easy ingestion by phagocytes.
*Antibodies bind to toxins produced by bacteria, making them harmless. They also bind to viruses, making them inactive.
*Antibodies bind to bacterial cells, causing the cells to burst and die.
State the two types of specific immunity.
Active immunity - person produces antibodies:
*Natural:
Person is infected with the disease.
*Artificial:
Obtained through vaccination.
Passive immunity - antibodies given to the person:
*Natural:
Baby gets antibodies from the mother’s milk or through the placenta.
*Artificial:
Antibodies are injected into the body.
What is vaccination?
Vaccination involves receiving a vaccine for the body to induce active immunity.
How does a vaccine work?
1) Each lymphocyte has a different protein on its surface. These surfaces are known as receptors.
2) Only the specific lymphocyte can bind to the pathogen because its receptor is complimentary in shape to the antigen.
3) The lymphocyte divides to produce multiple identical copies of itself.
4) Some lymphocyte release antibodies.
5) Some lymphocytes remain in the bloodstream as memory cells.
How do antibiotics work?
Antibiotics are drugs used to treat bacterial and some fungal infections.
They interfere with some aspects of growth or metabolic activities of the pathogens.
Antibiotics inhibit:
* Synthesis of bacterial cell wall
* Protein synthesis
* Enzyme action
* Cell membrane
Why do antibiotics kill bacteria but not viruses?
Viruses:
Have a protein coat.
Cell membrane absent.
Cytoplasm absent.
Ribosomes absent.
Bacteria:
Have a cell wall.
Cell membrane present.
Cell membrane present.
Ribosomes present.
Antibiotics does not affect viruses because viruses do not have structures that can be targeted.
How do bacteria develop resistance to antibiotics?
When bacteria are exposed to certain chemicals or agents, their genes might change. This is known as mutation.
Some mutations allow bacteria to become resistant to antibiotics. When these bacteria reproduce, the mutation will be passed on to future generations.
Why do doctors always tell their patients to complete
the full course of antibiotics?
Taking the full course of antibiotics ensures that the infection is properly treated. This prevents the survival of bacteria that may become antibiotic-resistant.
