Human Defences

Question 1

what are the 2 types of human defences

Answer 1

chemical defences
physical barriers

Question 2

what are chemical defences

Answer 2

a chemical produced that is used to kill or make pathogens inactive

Question 3

what is the purpose of physical barriers

Answer 3

make it hard for pathogens to enter the body

Question 4

what are 2 chemical defences

Answer 4

lysozyme enzyme in tears and saliva
hydrochloric acid in the stomach

Question 5

what are 2 physical barriers

Answer 5

skin
mucus

Question 6

how is the lysozyme enzyme a chemical defence

Answer 6

it breaks down bacteria cell walls

Question 7

how is hydrochloric acid a chemical defense

Answer 7

it kills pathogens in foods and drinks

Question 8

how is skin a physical barrier

Answer 8

it forms a protective barrier that is too thick for most pathogens to get through

Question 9

where is sticky mucus found

Answer 9

in the breathing passages and lungs

Question 10

how does sticky mucus work

Answer 10

they trap pathogens, the cilia on the cells lining the lungs will move in a wave-like motion moving mucus and trapped pathogens out

Question 11

what are the 2 types of white blood cells

Answer 11

lymphocytes and phagocytes

Question 12

what are phagocytes

Answer 12

white blood cells that are not specific that engulf pathogens

Question 13

how do lymphocytes work

Answer 13

every pathogen has unique antigens. the body mutates lymphocytes to create a lymphocyte that has antibodies that fit the antigens. once the correct lymphocyte is found it will divide to produce more of them. they will release lots of antibodies which will stick to the pathogen and destroy it

Question 14

how do lymphocytes deal with secondary infections

Answer 14

some of the lymphocytes will stay in the blood as memory lymphocytes so that they are ready to respond immediately if the pathogen returns

Question 15

what is immunisation

Answer 15

when a person is given a vaccine to prevent them from becoming ill

Question 16

how do vaccines work

Answer 16

1. a vaccine contains antigens from the pathogen, often in the form or dead or weakened pathogens
2. the person’s lymphocytes produce antibodies against the pathogen and also memory lymphocytes
3. when the person becomes infected for real, the memory lymphocytes will give a very rapid secondary response to the pathogen as it already has the memory lymphocytes. this will prevent the person from becoming sick

Question 17

what are 3 advantages of immunisation

Answer 17

immunity can be produced without being ill
lasts a long time
herd immunity

Question 18

what is herd immunity

Answer 18

when most of the people in a community are vaccinated the unvaccinated people are less likely to catch the disease. as the disease will be contained

Question 19

what are 2 negatives of immunisation

Answer 19

some people get a mild reaction
very rarely a person as a major harmful reaction