5.1 - Defence Mechanisms

Question 1

what do antigens recognise (4 points):

Answer 1

pathogens
* recognises antigens being foreign and activates cells to destroy the pathogen

abnormal body cells
* cancerous or infected cells display abnormal antigens - trigger immune response

toxins
* antigen molecules themselves and can be recognised

cells from other organisms of the same species
* can have different antigens to own body cells - can cause rejection

Question 3

Inflammation (physical and chemical barriers) - (symptoms observed (4 points), what can it be triggered by, what are 2 ways in which blood vessels are affected)

Answer 3

swelling, heat, redness, pain at the site of infection

triggered by damaged tissues

chemicals released can make the blood vessels;
* dilate - blood flow increases, becoming hotter to prevent pathogens reproducing
* walls are more permeable - lack tissue fluid and causes swelling (isolates any pathogens in the damaged tissue)

Question 4

Blood clotting and wound repair (physical and chemical barriers) - (possible danger, what is the body response to this, and what does this allow the body to do, what happens when healed)

Answer 4

• a cut to the skin can be a possible entry for pathogens
• blood clots to seal wounds - which forms a scab
• skin can repair itself and epidermal cells under the scab divide - damaged blood vessels regrow and enlargen fibres are used to provide strength to new tissue
• once thickness is achieved, scab breaks and wound is healed

Question 5

Expulsive reflexes (physical and chemical barriers) - (type, and how - 2 points)

Answer 5

• coughing and sneezing (expels foreign objects) from gas exchange system
• vomiting and diarrhoea - expels the contents of the gut along with any pathogens present

Question 6

Mucous membranes (physical and chemical barriers) - (what type is it and where and what does it do?)

Answer 6

• physical and chemical
• parts of the ear, nose, throat and digestive tract are lined by mucous membranes

secrete mucus to trap pathogens and use lysosomes to destroy them

Question 7

Skin (physical and chemical barriers) - (what type of barrier is skin and what does it do - 2 points)

Answer 7

acts a physical barrier
* blocks pathogens from entering the body

acts as a chemical barrier
* produces sebum which lowers the pH to inhibit pathogens from growing

Question 8

Specific defences (response time and what type of specific response do they have?)

Answer 8

• slower
• give a specific response for each type of pathogen

Question 9

What are non-specific defences? (how quick do they act and what is their specific response to pathogens)

Answer 9

• they act quickly
• not the same response for all pathogens

Question 10

what are the 4 types of pathogens (what are they, what do they do specifically?)

Answer 10

bacteria
* produce toxins that damage cells

viruses
* use host cells that replicate before bursting out and destroying cells

protists
* take over cells and break them open

fungi
* digest living cells to destroy them and some produce toxins