human defence system Flashcards
define pathogen
an organism that causes disease
define immunity
the ability to resist disease
give the two parts of the human defence system that allows the body to resist infection
general defence system, specific defence system
the general defence system is non-specific, what does this mean?
it acts against all pathogens
true or false, the general defence system acts as a barrier to all pathogens which attemp to gain entry into the body
true
what does the first part of the general defence system consist of
skin, mucous membranes and secretions
what does the second part of the general defence system consist of
white blood cells and chemicals
give the function of the skin
provides a structural barrier to infection
give the function of clotting
prevents blood loss and prevents entery of further pathogens
give the funtion of lysozyme
an enzyme found in sweat, tears and saliva- it attacks and breaks down bacterial cell walls
give the function of sebaceous glands
found in skin- produce chemicals that are released in sebum (oil) that kills bacteria
give the funtion of mucous
traps pathogens and prevents their entry
give the funtion of cilia
tiny hairs that line the respiratory system which beat and create a current to move mucous back up the respiratory system so it can be swallowed into the stomach
give the funtion of acid in the general defence system
e.g HDl in stomach kills pathogens
give a function of beneficial bacteria in the general defence system
some can produce lactic acid which prevents the growth of pathogens
what does the second line of general defence consist of?
destruction of pathogens by white blood cells, production of a series of proteins that kill or prevent pathogens from reproducing, the inflammatory response
what are phagocytic white blood cells?
white blood cells called phagocytes that engulf and destroy any bacteria, viruses or other micro-organisms
explain the mechanism of phagocytes (phagocytosis)
cells which are damaged by micro-organisms release chemicals to attract white blood cells. some large phagocytes called macrophages move around in bodily fluids e.g lymph. they destroy and filter out pathogens by grabbing onto the pathogen with receptors, surrounding it and then digesting it
write a short note on defence proteins
these are proteins that get activiated by an infection and destroy viruses and pathogens. the set of around 20 proteins found in blood plasma is called compliment
what are interferons
are another set of defence proteins that prevent viral multiplication- limiting spread of viral infections e.g cold and flu
explain what happens during inflammation
infected cells release a chemical that causes blood capillaries to dilate and become more porous. this causes localised swelling, redness, headaches and pain. causes more white blood cells to come to the area the fight the infection. inflammation can occur over all over the body which can cause increased body temperature (fever) which affects the ability of some bacteria and viruses to reproduce
what’s another name for the specific defense system
the immune system
what does the immune system do
it attacks specific pathogens by producing antibodies or works when wbcs destroy body cells that are infected by a particular pathogen
where are lymphocyctes and monocytes formed
bone marrow
where do lymphocytes and monocytes move to after formation
blood vessels and parts of the lymphatic system
what do monocytes turn into
macrophages
what can macrophages detect
they recognise foreign molecules called antigens present on the surface of pathogens
explain how antigens stimulate antibodies
when the macrophage digests a pathogen, the antigen is displayed on the surface of the macrophage- stimulating production of antibodies
give two ways lymphocytes fight infection
some attack body cells that contain antigens on their surface. others produce antibodies
define antigen
a foreign molecule that stimulates the production of antibodies
define antibody
protein produced by lymphocyctes in response to an antigen
how many antibodies does a specific antigen produce
one
what do antibodies do
prevent viruses and bacteria from entering new host cells- pathogens destroyed by phagocytes
what happens when antibodies inactivate pathogens
they clump together and allow phagocytes to destroy the pathogens
what do antibodies trigger
complement system- bursts pathogenic cells.
what are memory cells
antibody-producing lymphocytes that remain in the body for a long time
what do memory lymphocytes do
they rapidly produce large amounts of a specific antibody if a similar antigen enters the body
how long does it take the body to produce the maximum number of antibodies on first contact
14 days after first contact with an antigen
how long does it take for antibodies to be produced on subsequent contact with the same antigen
5 days
how can we suffer from colds and flus more than once?
different forms… mutations
define induced immunity
the ability to resist disease caused by specific pathogens by the production of antibodies
give two types of induced immunity
active and passive
exaplin active immunity
involves the production of a person’s own antibodies in response to antigens. it is long lasting as the lympocytes live for a long time in the body
explain the two ways active immunity can occur
natural active immunity - pathogens enter the body in the normal way. artificial active imunity - occurs when a pathogen is medically introduced into the body
define vaccine
a non-disease causing dose of a pathogen which trigger the production of antibodies without suffereing the full symptoms of the infection
explain passive immunity
occurs when individuals are given antibodies that are formedby another organism- provides short term resistance
explain the two ways passive immunity can occur
natural passive immunity- when a child gets antibodies from its mother. artificial passive immunity - when a person is given an injection containing antibodies made from another organism e.g anti-tetanus injection
explain the structure of a lymphocyte
large round nucleus with very little cytoplasm
name the two different types of lymphocytes and where they mature
B-lymphocytes (B CELLS) and T-lymphocytes ( T CELLS). B cells mature in the bone marrow, T cells mature in the thymus gland
where do B cells go once they’ve matured in the bone marrow
they go to lymphatic tissue e.g spleen and lymph nodes
what happens when a B cell comes into contact with an antigen
it multiples and produces large amounts of the required antibody
how do antibodies inactivate antigen
they attach to them allowing the phagocytes to dispose of them or by activating the complement system to burst the cells
where do T cells move to from the bone marrow
thymus gland
do T cells produce antibodies
no
explain helper T-cells
these recognise antigens on the surface of other WBCs especially macrophages. they stimulate the multiplication of correct B-cells which will produce the correct antibodies
explain what killer T cells do
they attack and destroy abnormal body cells e.g virus/cancer infected cells. they are stimulated by chemicals produced by helper T cells. they release protein called perforin which forms pores in the membrane of the abnormal cells. this allowes water and ions to flow in and case the cell to swell and burst
explain what supressor T cells do
these are stimulated to grow by specific antigens and grow slowly. they become active after the antigen has been destroyed. they inhibit B cells, other T cells and macrophages. they turn of the immune response when the infection is over
explain what memory T cells do
these can survive for a long time. if the same pathogen re-enters a person’s body they quickly stimulate memory B cells to produce large amounts of the correct antibody. they also trigger the production of killer T-cells. they are responsible for lifelong immunity from infections
