Flashcards in CH-10 PATHOGENS AND IMMUNITY Deck (16)
Loading flashcards...

What is a pathogen?

an organism that causes disease


Describe three ways in which pathogens can be transmitted from one person to another,

by direct contact; in droplets in the air, in food and water, via a vector


outline four ways in which the body prevents pathogens from entering

for example, a layer of dead cells covering the skin, blood clotting; cilia and mucus in the respiratory passages; hydrochloric acid in the stomach.


What is active immunity?

defence against a pathogen by antibody production in the body.


What is passive immunity?

short-term defence against a pathogen by antibodies acquired from another individual, such as from mother to infant.


What is a transmissible disease?

a disease in which the pathogen can be passed from one host to another


What are the two ways in which the pathogen can be passed from one host to another.

Direct contact – the pathogen is passed directly from one host to another by transfer of body fluids such as blood or semen
Indirect contact – the pathogen leaves the host and is carried in some way to another, uninfected individual


Name the four ways in which pathogens can be transmitted?

1. Droplets in air- common cold, influenza
2. By food /water- cholera, typhoid
3. By a contact with contaminated surfaces- atheletes foot, salmonella
4. Insect bites- malaria, dengue fever


Name the defense systems our body has against pathogens.

1. Mechanical barriers- skin, hair in the nose
2. Chemical barriers- mucus, stomach acid
3. Cells- by phagocytosis, production of antibodies


Brief how our immune system destroys the pathogens .

1. All cells have proteins and other substances projecting from their cell membrane. These are known as antigens and are specific to that type of cell.
2.Lymphocytes have the ability to ‘read’ the antigens on the surfaces of cells and recognise any that are foreign
3.They then make antibodies which are a complementary shape to the antigens on the surface of the pathogenic cell
4. The antibodies attach to the antigens and cause agglutination (clumping together)
5. This means the pathogenic cells cannot move very easily
6.At the same time, chemicals are released that signal to phagocytes that there are cells present that need to be destroyed


How do people become immune to certain diseases?

1. The initial response of a lymphocyte encountering a pathogen for the first time and making specific antibodies for its antigens can take a few days, during which time an individual may get sick
2.Lymphocytes that have made antibodies for a specific pathogen for the first time will then make ‘memory cells’ that retain the instructions for making those specific antibodies for that type of pathogen
3.This means that, in the case of reinfection by the same type of pathogen, antibodies can very quickly be made in greater quantities and the pathogens destroyed before they are able to multiply and cause illness
4.This is how people can become immune to certain diseases after only having them once
5.It does not work with all disease-causing microorganisms as some of them mutate fairly quickly and change the antigens on their cell surfaces
6.Therefore, if they invade the body for a second time, the memory cells made in the first infection will not recall them as they now have slightly different antigens on their surfaces


How can active immunity be acquired?

- vaccination
- by getting infected by the pathogen



How can passive immunity be acquired?

- Injecting antibodies where the individual is already infected
- From mother to infant- antibodies passes onto the infant as a temporary protection, as his immune system is not strong enough to fight these infections.

FAST ACTING BUT SHORT LASTING - as the body doesnt make memory cells in passive immunity.


Brief disease caused by Immune system.

1. the lymphocytes (immune system ) starts attacking its own body cells
2. In this situation certain type of body cells are targeted by the lymphocytes and antibodies are made against them. - EG type 1 diabetes
3. People suffering from type 1 diabetes can no longer make their own insulin as the lymphocytes starts destroying the pancreatic cells that are responsible for the production of the insulin.


Explain the process of vaccination.

o harmless pathogen given which has antigens-In this weakened state, the pathogen cannot cause illness but can provoke an immune response
o antigens trigger an immune response by lymphocytes which produce antibodies
o memory cells are produced that give
long-term immunity
The antibodies target the antigen and attach themselves to it in order to create memory cells
The memory cells remain in the blood and will quickly respond to the antigen if it is encountered again in an infection by a ‘live’ pathogen
As memory cells have been produced, this immunity is long-lasting


How does Vaccination Control the Spread of Disease

If a large enough percentage of the population is vaccinated, it provides protection for the entire population because there are very few places for the pathogen to breed-This is known as herd immunity
Herd immunity prevents epidemics and pandemics from occurring in population.

If the number of people vaccinated against a specific disease drops in a population, it leaves the rest of the population at risk of mass infection, as they are more likely to come across people who are infected and contagious
This increases the number of infections, as well as the number of people who could die from a specific infectious disease