LEAVING CERT BIOLOGY THE HUMAN DEFENCE SYSTEM

Question 1

define a pathogen

Answer 1

a pathogen is a foreign body or cell that causes disease

Question 2

what do pathogens include

Answer 2

bacteria, viruses and fungi

Question 3

what two defence systems do humans use to help defend themselves against pathogens

Answer 3

the general defence system and the specific defence system

Question 4

define the general defence system

Answer 4

the general defence system tries to defend us against all pathogens

Question 5

briefly explain how the general defence system works

Answer 5

the general defence system acts by preventing the entry of pathogens into the body or by destroying them when they do enter

Question 6

name 6 things from the general defence system that prevent entry of pathogens

Answer 6

skin, lysozyme, clotting, mucus, cilia and acid

Question 7

name 4 things from the general defence system that destroy pathogens in the body

Answer 7

white blood cells, complement, interferons and inflammation

Question 8

how does the skin prevent the entry of pathogens

Answer 8

skin acts as a barrier to the entry of pathogens

Question 9

how does lysozyme prevent the entry of pathogens

Answer 9

lysozyme is an enzyme that is found in sweat, tears, saliva and urine. It bursts the walls of bacteria, leading to their death

Question 10

how does clotting prevent the entry of pathogens

Answer 10

clotting helps to prevent the entry of pathogens once our skin is damaged

Question 11

how does mucus prevent the entry of pathogens

Answer 11

mucus in the respiratory system is sticky. it traps pathogens

Question 12

how does cilia prevent the entry of pathogens

Answer 12

cilia in the respiratory system sweep the mucus up from the air passages. the mucus and the pathogens then passes to the stomach

Question 13

how does acid prevent the entry of pathogens

Answer 13

acid in the stomach [hydrochloric acid] destroys pathogens. lactic acid in the vagina acts in the same way

Question 14

how do white blood cells destroy pathogens in the body

Answer 14

white blood cells surround and destroy pathogens that enter the body. these cells are often called phagocytes. large phagocytes are called macrophages

Question 15

how does complement destroy pathogens in the body

Answer 15

complement is a set of proteins found in the plasma. complement is activated by infection and causes bacterial cell walls to burst

Question 16

how do interferons destroy pathogens in the body

Answer 16

interferons are another set of proteins. they are produced by body cells that become infected by viruses. interferons prevent the multiplication of viruses

Question 17

how does inflammation destroy pathogens in the body

Answer 17

inflammation results in heat, redness and swelling around the site of infection. this increases the number of white blood cells in the area of infection. if the inflammation occurs all over the body it is called a fever

Question 18

define the specific defence system/ the immune system

Answer 18

the specific defence system/ the immune system acts against one type of pathogen or antigen

Question 19

define Antigen

Answer 19

an antigen is a foreign substance that stimulates the production of antibodies

Question 20

define antibody

Answer 20

an antibody is a protein produced by white blood cells in response to an antigen

Question 21

antigens are antibody generating molecules. yes or no

Answer 21

yes

Question 22

where are antigens found

Answer 22

antigens are found on the surface of pathogens such as viruses and bacteria

Question 23

what are antigens associated with

Answer 23

antigens are associated with pollen grains, blood transfusions, transplants and cancer cells

Question 24

where are B cells made and mature

Answer 24

bone marrow

Question 25

what happens to B cells once they mature

Answer 25

B cells move to the lymph nodes

Question 26

what do B cells produce

Answer 26

antibodies

Question 27

where are T cells made, mature and activated

Answer 27

made in bone marrow, mature and activated in the thymus gland

Question 28

where is the thymus gland located

Answer 28

the chest

Question 29

what do T cells not produce

Answer 29

antibodies

Question 30

name two types of lymphocytes

Answer 30

b cells and t cells

Question 31

what type of cells are lymphocytes

Answer 31

white blood cells

Question 32

name four different types of T cell

Answer 32

helper T cells
killer T cells
suppressor T cells
memory T cells

Question 33

what do helper T cells do

Answer 33

helper T cells recognise antigens on monocytes

Question 34

what do killer T cells do

Answer 34

killer T cells attack and destroy abnormal body cells

Question 35

what do suppressor T cells do

Answer 35

suppressor T cells inhibit B cells and killer T cells

Question 36

what do memory T cells do

Answer 36

memory T cells stimulate B cells and killer T cells to multiply if the same antigen enters the body again

Question 37

what is induced immunity

Answer 37

induced immunity is the ability to produce antibodies against specific antigens

Question 38

what is active induced immunity

Answer 38

active induced immunity means that the body produces its own antibodies

Question 39

what are the two types of active induced immunity.

Answer 39

natural and artificial

Question 40

define a vaccine

Answer 40

a vaccine is a non reproductive does of an antigen designed to stimulate antibodies

Question 41

define passive induced immunity

Answer 41

passive induced immunity happens when antibodies pass from one organism to another [usually from the mother to her baby]

Question 42

name two types of passive induced immunity

Answer 42

natural and artificial