Human Defence System Flashcards
pathogen
disease causing micro organism
immunity
ability to resist infection
general defence
prevents the entry of microbes by acting as a barrier and destroying all microbes once they are within the body
it is non specific, attacks all pathogen types
specific defence
identifies antigen and attacks particular pathogens using specific antibodies or white blood cells
lymphocytes
type of white blood cell that kills a pathogen by producing antibodies or killing a body cell that displays an antigen
monocyte
type of white blood cell that develops into a macrophage, that engulfs a pathogen and displays antigens on itself, stimulating the production of antibodies
antibody
proteins produced by lymphocytes in response to an antigen
their role is to inactivate antigens
antigen
foreign molecule that stimulate the production of antibodies
vaccination
non disease causing dose of the pathogen that is introduced into an organism to stimulate the production of antibodies
induced immunity
when the body contains specific antibodies against particular antigens
active immunity
when a person can produce their own antibodies against a disease
passive immunity
when a person cannot produce their own antibodies against a disease and receives antibodies that have been made by another organism
autoimmune disease
when part of the body is attacked by its own immune system
first line of defence
skin mucus HCI lysozyme bacteria
first line of defence SKIN
physical barrier preventing entry of pathogens, sebaceous glands to produce sebum that kills bacteria
first line of defence MUCUS
traps pathogens and cilia push mucus out, pathogens are then swallowed and killed in the stomach by HCI
cilia
small hairs lining the tubes of the respiratory system
first line of defence HCI
in stomach
kills pathogens
first line of defence LYSOZYME
bursts bacteria which allows the entry of water to their cells
first line of defence BACTERIA
lactic acid produced in the vagina inhibits the growth of pathogens
second line of defence INFLAMMATION
infected cells release a chemical that causes blood capillaries to dilate
swelling and redness is caused at the site of infection, number of WBCs at the site of infection increases
fever can occur, body temp increases which interferes with reproduction of some bacteria and viruses
second line of defence WBCs
phagocytes engulf and destroy micro organisms
complement defence proteins
activated by infection, produce holes in bacterial walls causing the bacterial cells to fill with fluid and burst
interferon defence proteins
released by cells infected by viruses, prevents the multiplication of viruses and limits the spread of virus infection
specific immune system
identifies antigen and attacks particular or specific pathogens using specific antibodies or WBCs
organs/glands specific to the immune system
tonsils
lymph nodes
spleen
thymus gland
white blood cells
formed in bone marrow and some mature in spleen
no nucleus present, no definite shape
less numerous than RBCs
defend against disease by engulfing and destroying cells and displaying antigens or producing antibodies
types of lymphocytes
T cells: dont produce antibodies
B cells: produce antibodies
T cells
form in bone marrow mature in thymus gland helper t cells killer t cells suppressor t cells memory t cells
helper t cells
recognise antigens, activate killer t cells
stimulate b cells
killer t cells
recognise the infected cell, produce perforin to kill infected cells - perforates cell membrane
suppressor t cells
stop immune response by inhibiting b cell or t cell production
memory t cells
remember antigen and survives a ling time to allow long term protection
b cells
form in bone marrow
mature in red bone marrow
plasma b cells
memory b cells
plasma b cells
antigens recognised, plasma b cells multiply
antibodies specific to the antigen produced in response
antigen inactivated
antigen disposed: by phagocytes or complement system
memory b cells
survive long after infection
convert plasma b cells in response to infection when it returns, secondary response (active immunity). therefore, these cells respond more rapidly than original b cells
antigen response by b lymphocytes
- pathogen displays antigens
- b lymphocytes recognises antigen and produces specific antibodies in response to the antigens
- antibodies bind to antigens and lymphocytes engulf and destroy pathogen
active vs passive immunity
active - longer lasting
passive - shorter lasting than active, needed for the fast response to infection
an antibody may be given instead of vaccination if
the infection has already occurred or is possibly very dangerous
reasons we don’t get the same infection twice
lymphocytes produce more antibodies faster than first infection, so smaller amounts of antigens present
how antibiotic resistance develops
not completing a full course of antibiotics or misusing them
bacteria mutate and acquire resistance, this resistant gene is carried in the plasmid
resistant plasmid is passed on
why are antibiotics not prescribed for the flu
not effective against viruses
flu is caused by influenza virus
antibiotics are prescribed to kill bacterial infections
immunosuppressants
antirejection drugs taken by organ transplant patients or to treat autoimmune diseases
these inhibit or prevent the activity of the immune system
people on these are more prone to infection
why covid affected older people
immune system gradually declines in a process called immunosenecence
why covid doesnt affect children
t cells are mostly untrained, greater capability to respond to new viruses
children regularly catch common cold, antibodies give some form of protection
