Chapter 12.5 Flashcards
(24 cards)
Give examples of non-specific defences?
Skin barrier
Airways of the gas exchange have lined with mucous membranes that secrete sticky mucus
Acid in the stomach, lysozymes in tears and urine
Expulsive reflexes (e.g. coughing, sneezing)
What are the 2 lines of defence against invasion of pathogen? What separates the two (in terms of function)?
Primary non-specific defence = System is deployed very rapidly and always present. This defends against pathogens in the same way.
Specific immune system = this one works specific to each pathogen but is slower to respond
How does expulsive reflex defend against pathogens?
Coughs and sneezes - help eject pathogen-laden mucus from the gas exchange system
Were vomiting and diarrhoea - expel the contents of guts along with infective pathogens
How does skin help defend against pathogens?
Skin cover that help stop pathogens from entering the body
Skin has flora of healthy microorganisms that outcompete pathogens for space on the body surface
Skin produces sebum (oily substance) that inhibits the growth of pathogens
How does lysozymes/acid in the stomach/ help defend against pathogens?
It helps prevent pathogens getting into our bodies
How does blood clotting work to heal wounds?
When you cut yourself…
1) Platelets come into contact with collagen in skin or wall of damaged blood vessel they adhere and begin secreting several substances:
(Substances formed) : Throboplastin - An enzymes triggers a cascade of reactions resulting in the formation of a blood clot (thrombus)
(Substances formed) : Serotonin - Makes the smooth muscles in the walls of the blood vessels contract, so they are become narrow and reduce the supply of blood to an area.
2) After the clot dries out forming a hard, tough, scab that keeps pathogens out. (FIRST STAGE)
3) Epidermal cells then are formed below the scab, sealing the wound permanently while damaged vessels regrow.
4) Collagen fibres then deposited and give the new tissue strength. Once the epidermis reaches normal thickness the scab sloughs off and wound is healed
How does the body tract (e.g. gaseous exchange) lined by mucous membranes defend against pathogens?
- By secrete sticky mucus that traps microorganisms and contain lysozymes, which destroy bacterial and fungal cell walls.
- Mucus that contain phagocytes that remove remaining pathogens.
What are the characteristics of inflammation?
Pain, Heat, Redness and swelling of tissue
What causes inflammation?
An inflammatory response which is localised response to pathogens or to damage or irritants at site of the wound
When are mast cells activated? What is their function?
- Activated in damage tissue
- Releases chemicals called histamines and cytokines (which they carry out specific functions)
What is the function of Histamines? (In inflammatory response)
- It makes blood vessels dilate causing localised heat and redness. Which help prevent pathogens reproducing
- Makes blood vessels walls more leaky so blood plasma is forced out - which flows out as tissue fluid. Causing swelling and pain
What is the function of cytokines? (In inflammatory response)
Attract white blood cells (phagocytes) to the site. Which then dispose if pathogens by phagocytosis
How does phagocytosis?
- Pathogens produce chemicals that attract phagocytes
- Phagocytes recognise non-human proteins on the pathogen. This pathogen is a response to the specific type of pathogen
- The phagocyte is then engulfs the pathogen and encloses the vacuole called phagosome
- The phagosome engulfs the pathogen and encloses it in a vacuole called phagolysosome
- Enzymes from the lysosome digest and destroy the pathogen
How is cytokines produced during phagocytosis?
Cytokines are produced when phagocytes are engulfed into the pathogen
What is the function of Cytokines after phagocytosis?
- Act as cell signalling molecules informing other phagocytes are under attack and stimulating them to move to site of infection/inflammation.
- Also increase body temperature and stimulates specific immune system
How is fever an adaptation?
- It allows the specific immune system to work faster (as they work faster at high temperature)
- Fever or high temperatures inhibits pathogen production.
How do pathogens trigger fevers?
When pathogens invade the body, cytokines stimulates your hypothalamus to reset the thermostat and temperature goes up
What is the function of the hypothalamus?
Maintains the temperature in the brain
How do Opsonins work?
They bind to the to the pathogens and tag them so they can be more easily be recognised by phagocytes.
So phagocyte receptors on the cell surface membrane that bind to the common opsonins and engulf the pathogen
What is the function of opsonins?
They are chemicals that bind to pathogens and tag them so they can be easily detected by phagocytes
What are the 2 main phagocytes?
Neutrophiils
Macrophages
What are phagocytes?
Are specialised white cells that engulf and destroy pathogens
How does it take for a neutrophil to engulf and destroy a bacterium?
under 10 mins
What happens when macrophages digest a pathogen?
- When macrophages have digested a pathogen - it combines antigens from the pathogen surface membrane with special glycoproteins in the cytoplasm (called MHC)
- The MHC complex moves becoming an antigen-presenting cell (APC). These antigens now stimulate other cells involved in specific immune response.
