Human Defence System Flashcards
What is a pathogen?
An organism that causes disease
Immunity
The ability to resist infection
What are two parts of human defence system?
General
Specific
What is first life of defence
Barriers prevent entry of pathogen
Examples of first line
Skin, physical barrier
Clotting, blood clotts
Lysozyme, enzyme in sweat,tears,saliva-attack bacteria
Mucous, trap pathogens by sticking
Second line of defence?
Consists of white blood cells and chemicals that destroy any pathogens
What do phagocytic white blood cells do
Term for this?
Engulf and destroy harmful bacteria and virus
-phagocytosis
What are large phagocytes called
Macrophages
What do defence proteins do?
20 proteins found in plasma, activated by infections which destroy harmful pathogens
What are two types of defence proteins
Complement and interferon
What is complement?
Set of proteins in the blood system which are involved in chain reaction, result in bursting of pathogen
What is interferon?
Set of proteins produced by body cells infected by with virus, interferons spread to nearby cells stimulating them to prevent viral multiplication and thus reduce spread of virus
What is inflammation?
Infected cells release chemical that cause blood capillaries to be more pourous
Causes swelling redness heat and pain which brings more white blood cells to area
What does specific defence system do
Attacks particular pathogens
What do monocytes do?
Become macrophages which recognise specific pathogens and engulf them
Where are lymphocytes formed
Bone marrow
Where do B cells mature?
Bone marrow then moves to lymph nodes
Where do T cells mature
Thymus
What are the two B cells?
Plasma B cells
Memory B cells
What do plasma B cells do?
Produce antibodies
-monocytes and macrophages recognise antigen on pathogen ,engulf it, and display on surface
This stimulates plasma B cells to produce specific antibody
What is an antigen
A foreign molecule that causes production of antibody
What is an antibody
Proteins produced by white blood cells in response to antigens
What do antibodies do?
- Bind to pathogen, prevent entering from cell
- clump pathogens together to be engulfed by phagocyte
- Trigger complement system
What do memory B cells do
Remember pathogen and produce much quicker if infected again
What are the T cells?
- Helper T
- Killer T
- Suppressor T
- Memory T
What does helper T do?
Recognise antigen and stimulate plasma B cells and killer T
What does Killer T do?
release Perforin which breaks down cell membrane causing them to be flooded with water and burst
Suppressor T?
Turn off immune system to prevent access killer T being produced
Memory T?
Trigger B and T cells if reinfected
What is induced immunity?
Using antibodies to resist specific disease
What is active immunity?
Antibodies produced in persons body
What is passive immunity?
Antibodies from another organism bred the persons body
Difference between natural and artificial active immunity
Natural- pathogens enter body in natural manner e.g. Catching cold
Artificial- pathogen introduced into the body e.g. Vaccine
Difference between natural and artificial in passive immunity?
Natural- antibody enter body naturally e.g. Antibodies cross the placenta into feutus
Artificial- antibodies are injected into a person e.g. Anti tetnus injections
What is a vaccine ?
Non disease causing dose of pathogen which triggers production of antibodies
How do allergic reactions occur?
Over reaction of the immune system on harmless antigen
What is auto immune disease ?
Immune cells attacking the bodies own tissue e.g. Arthritis
