6.3 DEFENSE AGAINST INFECTIOUS DISEASE Flashcards
ESSENTIAL IDEA
the human body has structures and processes that resist the continuous threat of invasion by pathogens
PATHOGEN
disease causing organism bacteria protozoa viruses fungi
PRIMARY DEFENSE AGAINST PATHOGENS THAT CAUSE INFECTIOUS DISEASE
skin
mucous membranes
SKIN AS A DEFENCE
continuous: hard to find an opening
many layers/tough
dry
pH: not favourable to pathogens
lysozyme: enzyme break down pathogens
natural organisms: competitive exclusion by non-harmful microbes
MUCOUS MEMBRANE AS A DENFENCE
sticky mucous: traps invaders
pH: not favourable to pathogens
lysozyme: enzymes break down pathogen
natural organisms: competitive exclusion by non-harmful microbes
CLOTTING FACTORS
cause a series of reactions which end with fibrin (a protein) fibres forming a mesh across the wound site
PLATELETS
small cell fragments
alongs with damaged tissue release clotting factors in response to a wound
FIBRIN FIBRES
capture blood cells and platelets forming a clot
in the presence of air the clot dries to form a scab which shields the healing tissue underneath
WHY DOES BLOOD CLOT?
to prevent blood loss and the entry of pathogen
BLOOD CLOT SUMMARY
platelet/ cell damage clotting factors thrombin fibrinogen--> fribin fibres captures erythrocytes clot
BLOOD CLOT CONVERSION
the cascade results in the rapid conversion of fibrinogen to fibrin by thrombin
CAUSES AND CONSEQUENCES OF BLOOD CLOT FORMATION IN CORONARY ARTERIES
cholesterol deposit plaques atherosclerosis blood clots heart attack death
LEUKOCYTES
WBC
phagocytes
–> engulf
lymphocytes
- -> B cells
- -> T cells
- -> killer cells
INGESTION OF PATHOGENS BY PHAGOCYTIC WBC
gives non- specific immunity to diseases
PHAGOCYTOSIS
involves a phagocyte
PHAGOCYTOSIS STEP 1
detecting and moving towards a foreign material (pathogen) using chemotaxis
PHAGOCYTOSIS STEP 2
foreign material is ingested by endocytosis
PHAGOCYTOSIS STEP 3
lysosomes attach to the ingested vesicle (which encloses the foreign material) and release enzymes into it
PHAGOCYTOSIS STEP 4
the enzyme digests/ breaks down the foreign material
PHAGOCYTOSIS STEP 5
the remains of the foreign material are expelled from the phagocyte
INADEQUATE PHAGOCYTIC RESPONSE
if the infection becomes widespread
then lymphocytes which control the specific immune response are used
ANTIGENS
substance or molecule that causes antibody formation
ANTIBODY
globular protein that recognises a specific antigen and binds to it as part of an immune response
ANTIBODIES ARE SPECIFIC TO
certain antigens
IMMUNE RESPONSE IS TRIGGERED BY
non self cells, which is why matches are crucial in transplant and blood transfusion
PRODUCTION OF ANTIBODIES
many different lymphocytes exist
each type recognises one specific antigen
when the immune system is challenged by the invasion of a pathogen, the corresponding lymphocyte responds
it makes many clones of itself, each of which produces antibodies to the pathogen = clonal selection
some cloned cells remain as memory cells, ready for a second invasion by the pathogen
= immunity
CLONAL SELECTION
the right lymphocyte is selected and then cloned
ANTI BIOTICS
drugs used in the treatment and prevention of prokaryotic bacteria
ANTIBIOTICS ARE DESIGNED TO
disrupt structures or metabolic pathways in bacteria and fungi:
cell walls and membranes
protein synthesis (translation)
DNA/RNA synthesis
other metabolic
processes (enzyme function)
ANTIBIOTICS AND VIRUSES
metabolic pathways do not exist in viruses so antibiotics have no effect upon them
viruses are protected by host cell structure
ANTIBIOTIC RESISTANCE
indiscriminate use of antibiotics is leading to antibiotic resistance in bacteria
ANTIBIOTIC RESISTANCE AND NATURA SELECTION
an example of evolution by natural selection
bacteria mutate and resistance to an antibiotic naturally arises
bacteria divide rapidly thus a resistant strain of bacteria can quickly proliferate
over time strains of bacteria can become resistant to multiple strains of bacteria
FLOREY AND CHAIN
their experiments to test penicillin on bacterial infections in mice/ humans was successful
HIV
retrovirus: inserts its own RNA into the host cell
eventually HIV particles damages T cells
as a result the immune system is weakened and few antibodies can be produced
AIDS
syndrome caused by HIV
when a person’s immune system is too weak to fight off infections
develops when HIV is advanced
last stage of HIV
HIV transmission
breastfeeding oral sex child birth sexual intercourse blood to blood contact
