BIO SAC Flashcards
(16 cards)
What are viruses?
An infectious agent composed of genetic genetic material inside a caspid (protein coat). They cause disease through the lysis of cells during viral replication. They can’t replicate independently so they insert their genetic material into a host cell using its machinery to produce more viral DNA.
Are viruses cellular or non-cellular, extra or intracellular?
Viruses are non-cellular and intracellular
What is the innate immune system?
It is a non-specific response to foreign antigens (the react the same way regardless of the type of pathogen/antigen present). It responds very quickly to limit the spread of infection using chemical, microbiological and physical barriers.
What is a physical barrier?
Barriers the prevent or impede the entry of pathogens.
E.g: Intact skin, cilia, mucous
What is a chemical barrier?
Barriers that act to inhibit the growth or development of pathogens and/or destroy them.
E.g: Stomach acid the destroy bacteria that has been swallowed, lysosome enzymes in tears that destroy bacterial cell walls, acid in sweat.
What is a microbiological barrier?
The presence of non-pathogenic bacteria (known a normal flora) in the body prevents growth of pathogenic organisms as the compete for space and resources.
E.g: Presence of bacteria on skin, and lower gastrointestinal tract
What is the first line of defence?
The first line of defence consists of physical, chemical and microbiological barriers to keep pathogens out of an organism. It is innate.
What is the second line of defence
When pathogens breach the first line of defence the second line is the back up. It provides us with non-specific and immediate protection against potential pathogens.
What are phagocytes?
Phagocytes are cells that engage in phagocytosis, a process in which they consume and destroy foreign or dead material present in the body by engulfing it through the process of endocytosis. Once engulfed, lysosomes containing antimicrobial enzymes called lysozymes destroy the foreign or dead material.
E.g: neutrophils, macrophages and dendritic cells.
What are antigen-presenting cells
These cells not only consume and destroy foreign material, but they also present antigens from consumed material on their surface, called MHC Class II makers.
They use these markers to present the consumed antigens on their surface and interact with the adaptive immune system.
E.g: macrophages and dendritic cells, and B cells.
what are cytokines?
Phagocytes release cytokines which act as signalling molecules to attract other cells in the immune system to the site of injury/infection.
What are natural killer cells?
Natural killer cells are large granulated cells which target both abnormal and virally infected cells.
They have:
Killer inhibitory receptors (examines the surface of cells for MHC Class I markers)
Killer activation receptors (binds to certain molecules which appear on cells undergoing cellular stress, e.g. infected or cancerous cells).
If the killer activation receptor is activated it will initiate cell death, unless it is overridden by the killer inhibitory receptor detecting a sufficient number of MHC Class I markers.
Factors such as viral infection or cancer can destroy or suppress the production of MHC Class I markers.
What is the inflammatory responses purpose?
Eliminate the effects of an injury
Defend against potential pathogens
Clear out cells that may have been damaged or destroyed
Initiate repair
What are the stages of the inflammatory response?
It is a complex, non-specific process that always occurs in the same way regardless of the pathogen present or the injury that has occurred.
STEP 1:
When a pathogen enters the the body macrophages situated in the tissue become activated and, along with damaged cells, release cytokines. Additionally, mast cells are stimulated by cytokines and degranulate, releasing histamines.
STEP2:
The histamine released by mast cells travels to nearby blood vessels causing vasodilation.
This widens the blood vessels, increasing blood flow to the injury site causing swelling, redness and warmth.
Gaps in the vessel wall also increases its permeability to cells of the immune system
STEP3:
Vasodilation and the increased permeability of blood vessels allows for various innate immune system components to leave the bloodstream and enter the site of injury.
Phagocytes, including macrophages and neutrophils, are guided by the cytokines to the site of injury, where they phagocytose pathogens and digest them.
Complement proteins are attracted to pathogens and make it easier for phagocytes to destroy them.
What is the adaptive immune system?
It is designed to combat pathogens that have breached the first line of defence. It is specific, meaning it responds to each distinct pathogen in a unique and tailored way
And has immunological memory, meaning it produces cells that allow the body to respond to future re-infections quickly and effectively
