Unit 10 - defence against diseases

Question 1

What’s a Pathogen? ( 2)

Answer 1

• A pathogen is an organism that causes diseases.

- Most pathogens that cause disease in human bodies are bacteria or viruses

Question 2

What methods of transmission do pathogens have? ( 4-6 )

Answer 2

• Via air
• Contaminated food and drink
• Direct contact
• Insect vectors
• Body fluids
• Sexual activity

Question 3

What types of barriers ( first line of defence ) are there in our body? ( 2 )

Answer 3

• Mechanical barriers

- chemical barriers

Question 4

Describe the Mechanical barriers ( 2 )

Answer 4

• Dead outer layers of skin, which form a barrier to pathogen entry
• Hairs in nose, which trap larger particles that you breathe in

Question 5

Describe the Chemical barriers ( 3 )

Answer 5

• Hydrochloric acid in stomach, which denatures proteins in cell membranes of microorganisms, killing pathogen
• Mucus lining trachea and bronchi traps microorganisms.
• Cilia move mucus from lungs to throat, where it’s swallowed . HCl, as mentioned before, kills the pathogen

Question 6

What types of blood defences ( second line of defence ) are there in our body? ( 2 )

Answer 6

Phagocytes
-engulf bacteria & viruses into vacuoles where they’re digested and destroyed
Lymphocytes
-Produce antibodies, proteins that ahev effects on pathogens that ease their engulfment by the phagocytes

Question 7

What effects do the antibodies produced by the lymphocytes have on pathogens? ( 4 )

Answer 7

• Cause bacteria to agglutinate
• Stop flagella of bacteria from moving
• Neutralise toxins released by some bacteria ( these antibodies are called antitoxins )
• Weaken bacteria cell walls

Question 8

What are antigens? Describe them ( 4-5 )

Answer 8

• Antigens are the chemicals on the surface of pathogens
• Many are made of protein
• Each type of pathogen has different antigens
• They lock onto antigens of pathogens
• The ones made against antigens have a complementary shape to the antigen

Question 9

Why do you fall ill during a first infection ( frist time with a disease? ) ( 1-2 )

Answer 9

-It takes some days for your pathogens to make antibodies which can lock on to the specific antigens

Question 10

What is Active immunity? ( 2 - 3 )

Answer 10

• It takes place when a pathogen has entered your body for a second time
• The lymphocytes now produce lymphocytes much quicker, and kill the pathogens quickly before they can multiply

Question 11

Why is HIV such a serious infection? ( 1 )

Answer 11

-This is because it attacks and kills lymphocytes, making the body undefended against a disease without the capability to create antibodies

Question 12

What are memory cells? ( 4 )

Answer 12

• Some of the antibodies created by lymphocytes become memory cells
• They produce the “right” type of antibody to fight a specific disease
• They circulate in your blood in case an old pathogen attacks again
• Each time the same pathogen invades the body, more memory cells are produced, thus showing how the immune response is greater after each subsequent invasion.

Question 13

What is a Vaccine? ( 1 )

Answer 13

-An artificial way to gain active immunity without getting ill.

Question 14

How do vaccines work ?

Answer 14

• A weakend form of a disease antigen is injected into the body
• The body reacts to the anitgen by creating antibodies to attack it
• If the antigen ever enters the body again, the body’s immune system antibodies will be able to fight against it, because of a faster immune response