Unit 10 - diseases and immunity Flashcards
What is a pathogen?
Disease carrying organism.
Include: bacteria, fungi, protoctists
What is a host?
An organism infected by a pathogen
What are viruses?
- Particles consisting of a genetic material surrounded by a protein coat.
- Although not living organisms, they can still act as pathogens.
- not made of cells, don’t have cell membrane or cytoplasm
- do not show any of the 7 characteristics
- to reproduce, they insert their genetic material into a living host cell and use the material of the host cell to make a new virus
What is a transmissible disease?
A disease caused by a pathogen that can be passed from one host to another.
E.g. common cold - virus, athlete’s foot - fungus, cholera - bacterium
What are 2 methods of transmission?
Direct contact through bodily fluids such as blood
Indirect contact, such as from air, through water/food, contaminated surfaces or animals
What is a vector?
An organism that transmits the pathogen from an infected to a non-infected person.
What are the 2 types of first line defense + purpose?
- Mechanical barrier - barriers that prevent the entry of pathogens into the body such as skin, scab forming and ciliated cells (cilia move mucus and trapped particles away from the lungs)
- Chemical barriers - barriers in the body that trap and kill pathogens such as mucous membranes that produce sticky mucus which traps bacteria and stomach acid whose high acidity will kill swallowed pathogens
What is the second line of defense?
The immune system. It detects pathogens that enter the body and destroys them.
E.g. phagocytes (type of wbc) surround and engulf a pathogen, which is the process of phagocytosis , then destroys it
E.g. lymphocytes (type of wbc) produce antibodies, proteins which attach to pathogens and mark them for destruction
How to control the spread of disease:
- clean water supply - good for drinking, cooking, etc.
- good personal hygiene - washing hands, covering mouth when sneezing
- hygienic food prep - stored properly, kept away from vectors such as flies
- proper waste disposal - waste may attract insects that may act as vectors, so waste should be put away in covered containers
- treatment of sewage - far away from drinking water supplies
- vaccination - help control spread of disease
What is active immunity?
Immunity developed in response to a pathogen and involves the activation of memory cells. Could also be due to vaccination
What are antigens?
Substances that trigger the immune response and cause the production of antibodies. Each pathogen has its own antigen, with a unique shape.
Molecules on the surface of the pathogen.
What are antibodies?
Proteins produced by lymphocytes. An antibody for a particular antigen has a shape that fits/is complementary to the shape of that antigen.
Once the antibody attaches to the antigen, it can mark the pathogen for phagocytosis or cause the pathogen to break open and die
What is a primary response?
The immune response mounted when someone is infected by a pathogen for the first time, or vaccinated against it.
What is secondary response?
Immune response mounted after a re-infection by a pathogen. Response is quicker. Involved lymphocytes called memory cells.
What is a memory cell?
A cell that forms from a lymphocyte as the immune system responds to an infection. It remains in the bloodstream and can recognize/remember pathogens that infect after a first infection. It then differentiates to form antibody-producing lymphocytes that mount a secondary response.
If infected again, the memory cells respond quickly, causing more antibodies to be produced in a short space of time.Often, you will not even become ill as so many antibodies are produced.
What does being immune mean?
The state when the body has enough antibodies to resist pathogens and protect from infections
What is the aim of a vaccine and how does it work?
It aims to immunise people against infections by a particular pathogen without them needing to have the disease itself first.
A vaccine contains a small amount of material from the pathogen/ dead or weakened pathogens that cannot cause disease. The vaccine is introduced into the body, and the lymphocytes mount a primary response to the antigens from the pathogen. They make antibodies to target these antigens and they also produce memory cells. If a vaccinated person is then infected by the live pathogen, the memory cell will recognize it very quickly. A secondary immune response is mounted, which destroys the pathogens, often before symptoms develop.
What are immunization programs?
Programs where a particular vaccination is offered to everyone of a specific age.
When does herd immunity occur?
When a majority of the population are protected against infections by the pathogen because they are vaccinated.
