How Our Body Defends Itself Against Infectious Diseases Flashcards
WHAT ARE PATHOGENS?
A pathogen is a biological agent that causes disease or illness to its host
— they are microorganisms (bacteria and viruses)
HOW DO BACTERIA AND VIRUSES CAN MAKE US FEEL ILL
Bacteria released toxins and viruses that damage our cells
WHAT TYPE OF BLOOD CELL CAN DIGEST AND DESTROY PATHOGENS
+ the process
WHITE BLOOD
CELL
- The white blood cell surrounds the pathogen…
- It then digests it
HOW DO WHITE BLOOD CELLS KILL VIRUSES
- Your white blood cells make antibodies and memory cells
- The antibodies attach to the measles virus and kills them
- If the same virus returns to your body your memory cells know what antibodies to produce straight away
HOW ARE PATHOGENS USED IN VACCINATION
In vaccination, pathogens are introduced into the body in a weakened form.
The process causes the body to produce enough white blood cells to protect itself from the pathogens but without getting diseased.
WHAT IS BACTERIA (pathogens)
Bacteria are living cells and can multiply rapidly. They produce poisons and toxins
WHAT DISEASES CAN BE CAUSED BY BACTERIA (3)
- food poisoning
- typhoid
- whooping cough
WHAT ARE VIRUSES (pathogen)
Viruses can only reproduce inside host cells and they damage the cell when they do this. Once the cell bursts open, the viruses are passed out into the blood stream or airways
WHAT DISEASES CAN BE CAUSED BY VIRUSES (3)
- flu
- colds
- measles
WHAT HAPPENS WHEN PATHOGENS ENTER THE BODY
Once inside the body, pathogens reproduce
— viruses reproduce inside cells and damage them, while escaping to infect more cells
BUT the immune system destroys these pathogens
(White blood cells are important components of the immune system
WHAT CAN WHITE BLOOD CELLS DO
list 3
- engulf pathogens and destroy them
- produce anti bodies to destroy pathogens
- produce anti toxins that neutralise
WHAT IS ACTIVE IMMUNITY
Once you have been infected with a particular pathogen and produced anti bodies against it, some white blood cells remain
— if you become infected again with the same pathogen these white blood cells reproduce rapidly and the pathogens is destroyed - active immunity
WHO IS SEMMELWEISS AND WHAT DID HE DO
Semmelweiss reduced the number of deaths in hospitals from infectious diseases. 1948 be asked all doctors to keep washing their hands.
— demonstrated that hand washing could drastically reduce the number of women dying after childbirth
— he discovered that wards where babies were delivered only by mid wife’s had lower death rates than a ward where babies were delivered by doctors
WHAT ARE ANTIBIOTICS
Antibiotics are a type of medicine that stops the growth of or destroys microorganisms
They work in two ways,
• bactericidal
• bacteriostatic
HOW DOES A BACTERICIDAL ANTIBIOTIC WORK
A bactericidal antibiotic kills the bacteria and interferes with the formation of the bacterium’s cell wall or contents
E.g. penicillin
HOW DOES A BACTERIOSTATIC ANTIBIOTIC WORK
a bacteriostatic antibiotic stood bacterium from multiplying
WHAT ARE ANTIBIOTICS USED FOR
Treatment of an infection caused by bacteria
- targets microorganisms such as bacteria, fungi and paracites
- BUT is NOT affective against viruses
WHAT HAPPENS IF ANTIBIOTICS ARE OVERUSED
If antibiotics are over used there is a risk of the bacteria becoming resistant
WHAT ARE PAINKILLERS
pain killers relieve pain but does not cure diseases
— they block nerve impulses from the painful part of the body or blocks nerve impulses travelling to the part of the brain perceiving pain
WHAT IS MRSA
Meticillin Resistant staphylococcus Aureus
MRSA is a type of bacteria that’s resistant to a number of widely used antibiotics, it can be known as a super bug
HOW DO BACTERIA STRAINS DEVELOP RESISTANCE TO ANTIBIOTICS
This happens because of natural selection
In large populations of bacteria, there may be some cells that are not affected by the antibiotic.
• these cells survive and reproduce, producing even more bacteria that are not affected by the antibiotic
MAIN STEPS IN THE DEVELOPMENT OF RESISTANCE ARE
- Antibiotics kill individual pathogens of the non resistant strains
- Resistant individual pathogens survive and reproduce
- The population of the resistant pathogens increase
NEW ANTIBIOTICS MUST BE DEVELOPED FOR RESISTANT BACTERIA
WHAT DO VACCINATIONS DO
Vaccinations can make a person immune to diseases
WHAT DO VACCINES CONTAIN (4)
- live pathogens, treated to make them harmless
- harmless fragments of the pathogen
- toxins produced by pathogens
- dead pathogens
