non-specific animal defences Flashcards
define non-specific defences
innate immune system, made of phagocytes and barriers
- faster than specific
state 4 barriers the human body has to minimise the entry of pathogens into our cells
- skin
- mucous membranes
- eyelashes and nose hair
- tears
explain how the skin acts as an effective barrier to the entry of pathogens
- physical barrier
- skin flora of healthy microorganisms - outcompete pathogens on body surface
- sebum production to inhibit pathogen growth
explain how mucous membranes act as an effective barrier to the entry of pathogens
- secrete sticky mucus - traps microorganisms
- contains lysosomes (destroy fungal and bacterial cell walls) and phagocytes
name 4 expulsive reflexes and explain their value for protection against pathogens
- cough & sneeze - eject pathogen-containing mucus from gas exchange system, rapidly and in large quantity
- vomiting & diarrhoea - expel contents of gut along with infective pathogens also rapid and large quantity
explain the importance of blood clotting and the release of serotonin by platelets
- pathogens can enter body through cut and cause infection + blood loss
- serotonin makes smooth muscle in blood vessel walls contract to reduce blood supply to area
describe the processes involved in inflammatory response and explain their value for protection against pathogens.
mast cells activated in damaged tissue release histamines + cytokines
- histamines make blood vessels dilate = localised heat & redness - raised temp prevents pathogen reproduction
- histamines make blood vessels more leaky so blood plasma is forced out - swelling
- cytokines attract phagocytes to the site to carry out phagocytosis
describe how fever is initiated in response to invasion by pathogens and explain its value for protection against pathogens.
- when infected, cytokines stimulate hypothalamus to reset thermostat and temperature increases
- most pathogens reproduce best at or below 37*C - higher temp inhibits reproduction
- specific immune system works faster at higher temp
define phagocyte
specialised white blood cells that engulf and destroy pathogens
name 2 types of phagocytes
- neutrophils
- macrophages
describe the stages of phagocytosis
- pathogens produce chemicals that attract phagocytes
- phagocytes recognise non-self antigens on pathogen - not specific
- phagocyte engulfs pathogen and encloses it in a vacuole - phagosome
- phagosome combines with lysosome to form phagolysosome
- enzymes from lysosome digest and destroy pathogen
describe the role of the major histocompatibility complex in the cytoplasm of macrophages at the end of phagocytosis.
- glycoprotein
- macrophage combines antigens from pathogen surface membrane with MHC
- MHC moves pathogen antigens to macrophage surface membrane becoming an antigen-presenting cell which stimulates
define antigen presenting cell
cell that displays foreign antigens complexed with MHC on their surfaces
describe the role of cytokines in non-specific defences
cell signalling molecules informing other phagocytes the body is under attack
- stimulate phagocytes to move to site of infection/inflammation
- increase body temp and stimulate specific immune system
describe the role of opsonins in phagocytosis
chemicals that bind to pathogens and tag them so they can be more easily recognised by phagocytes
- antibodies act as opsonins
