Ch37: The Human Defence System Flashcards
What is a pathogen?
A disease-causing organism
What is immunity?
The ability to resist infection
What are the 2 lines of defence and definitions?
General defence system- a barrier to all pathogens attempting to gain entry to the human body
Specific Defence system: attacks particular antigens
Name and explain examples of the FIRST line of general defence
-Skin: physical barrier
-Platelets: clotting prevents entry of pathogens
-Mucus: traps pathogens
-Lysozyme: in sweat, tears, saliva and kills bacteria
-Cilia: lines respiratory system to move mucus into mouth where it can be swallowed
-Acid: in stomach kills many pathogens
Explain WBC’s in the second line of general defence
-When cells are damaged, they release chemicals that attract WBC’s
-WBC’s, called phagocytes, surround and ingest pathogens
-Large phagocytes, macrophages, either move around the body or remain in fixed places such as lymph nodes (filter &destroy pathogens in lymph)
Explain defence proteins in the seond line of general defence
-Complement is a set of about 20 proteins in blood plasma that destroy pathogens when activated
-Interferons prevent viral multiplication
Explain inflammation in the second line of general defence:
-Infected cells release chemicals that cause blood capillaries to dilate and become more porous
-Causes swelling, redness, pain and heat
-The heat prevents some bacteria and viruses from reproducing
Name and explain the parts of the specific defence system
Specific defence produces antibodies and directs WBC’s SPECIFICALLY to the infected cells
Monocytes: develop into macrophages which digest pathogens
Lymphocytes: attack body cells or produce antibodies
Antibody: protein produced by lymphocytes in response to specific antigens
Antigens: a foreign molecule that stimulates the production of antibodies
What is induced immunity?
Name 2 types of induced immunity
Induced: The ability to resist disease by producing antibodies
Active and Passive
Name and explain 2 types of induced immunity
Active immunity: the production of a person’s own antibodies in response to foreign antigens
Passive immunity: when individuals are given antibodies that were formed by another organism
Name and explain 2 types of active immunity
Natural active immunity: a pathogen enters the body in the normal way (infection)
Artificial active immunity: a pathogen is medically introduced into the body (vaccination)
Name and explain 2 types of passive immunity
Natural passive immunity: when a child gets antibodies from its mother
Artificial passive immunity: when a person is given an injection containing antibodies made by another organism
What is vaccination?
The administration of a non disease-causing dose of a pathogen to stimulate the production of antibodies
What is immunisation?
When we produce or are injected with antibdoies against a pathogen
Name the 2 types of lymphocytes and the differences between them.
Name the types of each type
B lymphocytes and T lymphocytes
B-cells mature in bone marrow
T-cells made in bone marrow but mature in thymus gland
B-cells: Plasma B-cells, Memory B-cells
T-cells: Helper T-cells, Killer T-cells, Surpressor T-cells, Memory T-cells
Explain Plasma B-cells
- Move to Lymphatic tissue when mature
-Each b-cell recognises only one specific antigen
-When it comes into contact with this antigen, it multiples and produces large amounts of antibodies
-The antibodies attach to the antigens and allow the cell carrying the antigen to be disposed of by phagocytes or the complement system
Explain Memory B-cells
-Most B-cells die off once the infection is overcome
-Memory B-cells remain alive for years to convert to plasma B-cells if the same antigen enters the body again
-This prevents the same pathogen infecting us more than once
Response of memory B-cells is faster because:
-less antigens
-Antibodies produced faster
-Greater numbers produced
Function B-cells (plasma)
Function of T-cells
B-cells: Produce antibodies
T-cells: attack cells that have an invading antigen on their membrane
Explain Helper T-cells
-Recognise antigens on the surface of other WBC’s
-Stimulate the multiplication of the B-cells that produce the antibody for the specfic antigen
-Stimulate killer T-cells to reproduce
Explain Killer T-cells
-Stimulated by helper T-cells
-Destroy abnormal human body cells (cancer cells)
-Release a protein called perforin that perforates the cell membrane
Explain Suppressor T-cells
Stop the immune response after the pathogen has been destroyed
Explain memory T-cells
-Survive for years after infection is eliminated
-Stimulate specific B-cells and Killer T-cells if the same infection enters the body later
-Responsible for lifelong immunity
