Body protection against infections Flashcards
Bacterial effects on body
1. Production of toxins - poisonous substances (metabolic wastes) that alters chemical reactions/affects cell function
2. Injury to cells and tissues - bacteria bore through cell walls/membrane, so there is leakage/fluid loss. Pathogens feed on some types of body cells.
3. Bacterial numbers - put pressure on surrounding organs, causing disruptions
Viruses
non-living - they have no organelles.
Must infect a living host cell to replicate/survive. They take over host cell’s metabolism.
cant survive long outside of host.
Viruses are specific in the types of cells they infect.
viral replication
1. Virus attaches to outside of host cell - it’s surface proteins (spikes) must attach to specific receptor sites on host cell surface.
2. Uncoated RNA enters lymphocyte
3. Viral RNA (the template) is made into viral ‘DNA’ using a viral enzyme
4. Host cell DNA in nucleus then integrates the viral DNA into its chromosomes
5. The viral genes are now transcribed into mRNA strand.
6. Viral mRNA is translated at the ribosomes into HIV proteins - generating new virus particles
Budding of new viruses (100’s) from host cell or new viruses are released by lysis/rupturing the host cell.
structural characteristics of bacteria
Microscopic, unicellular organism
outer cell wall, no membrane bound organelles
Prokaryote - has no nucleus, free floating or rings of DNA - plasmid
presence of flagellum
Classified according to shape
bacteriophage
Viruses which attack bacterial cells.
they multiply in bacterial cells causing lysis (breaking)/death of the host bacterium.
Structural characteristics of Viruses
seen using electron microscope
Classified according to their nucleic acid
Caspid (head) wt DNA or RNA - surrounded by taking over host cell’s DNA
Protozoa
microscopic, single celled organisms
Passed on by drinking infected water
fungi
Typically affects the skin, and mucous membranes
yeast, moulds, mushrooms
Ways of transmission of vectors
1. Transmission by contact - direct contact, actually touching an infects person. Indirect contact - touching an object that has been touched by an infected person.
2. Ingestion of food or drink - contaminated wt pathogens
3. Transfer of body fluids - when infected blood, saliva, semen -body fluids- come in contact with mucous membranes -nose, mouth, throat, genitals or blood stream.
4. Infection by droplets - pathogens in tiny droplets of moisture emitted when infected person breathes, talks, sneezes, coughs, sending infectious drops into air (the breathed in) or may settle on food or ustensils or eaten later. (Short range transmission)
5. Airborne transmission - when moisture in exhaled droplets evaporates - some bacteria and virus remain viable and can cause infection
6. Transmission by vectors - transfer of pathogens by animals: fly, insects, mosquitoes, fleas. Vectors are carriers of a disease (not affected by disease that they carry). An intermediate host of the pathogen.
Inflammatory response
body’s 2nd line of defence
Protective response of body (non-specific)
inflammation is a response that occurs when tissue is damaged; involves swelling, heat, pain + redness in affected areas.
Damage to the skin by heat/burns, chemicals, mechanical injury: cut, piercing with pin, infection, eg. Skin, scratch, mosquito bite, pimple.
Purpose of inflammatory response
1. Reduce spread of infection by destroying pathogen and prevent entry of any more
2. Remove damaged tissue and cell debris
3. Begin repair of the area (promote healing)
4 signs of inflammation
1. Redness (vasodilation)
2. Swelling (A.K.A oedema) (vasodilation)
3. Heat (warmth, hot) (vasodilation)
4. Pain: increased swelling due to increased blood supply; increased pressure on sensory neurone; or toxins/chemicals around sensory neurone, or damage to nerve endings.
Mast cells
(Specialised Leucocytes)
Are cells present in most tissues of the body (CT’s) filled wt granules. They stimulate/coordinate inflammatory responses.
complement system
A series of 20 or more proteins that aid in non-specific + specific immunity. Made by liver cells and macrophages.
present in blood plasma (normally inactive) and activated by pathogens.
When initiated, 1 protein -> activates the next, + so on- complex cascade of events.
inflammatory response
1. Stimulus = tissue damage or local chemical changes (bacteria present). Mast cells activated by complement proteins then release chemicals: histamines and heparin and other proteins into tissue fluid.
2. Histamine diffuses into capillaries causing them to vasodilate and become ‘leaky’ (more permeable/ gaps appear/ allowing larger cells and fluid to pass through). This increases blood flow to the area -> area swells, red and warm.
3. Heparin prevents immediate blood clotting in area around injury - but a clot of fluid does form (slows down m-o, decreases spread.)
4. Phagocytes (1st cells neutrophil + later monocytes) attracted to area by complimentary proteins + histamine chemicals. Phagocytosis occurs (engulf and digest dead cells & bacteria).
5. Pain receptors stimulated in inflamed area - to warn you damage occurred.
6. Pus (yellow liquid) forms = dead phagocytes (neutrophils) + dead microbes + cell debris + tissue fluid.
7. Mitosis produces new cells to repair damaged tissue. (Platelets form fibrin clot).
Fever
fever is where the body’s core temperature is reset at a higher temperature - due to an infection
An elevation of body temp above the normal level of 37.C
Non-specific, internal defence mechanism.
Actual body temperature and thermostatic set points are different during a fever. Must be brought in line (or will disrupt normal biochemical processes in the body)
when body temp lower then set point -> heating mechanisms activated
When body temp higher then set point -> cooling mechanisms activated.
Main causes of fever
1. Entry of pathogen/infections produces chemicals/pyrogens which triggers fever.
2. Body releases its own chemicals - pyrogens - that produce a fever.
steps of fever
1. During an infection (eg.cold, flu) activated macrophages (WBCs) inject pathogens + release chemicals- a pyrogen.
2. These pyrogens move to the hypothalamus (important role in ‘thermoregulation’) which resets the body’s thermostat… from the optimal core body to a higher set point. (No thermoreceptors involved).
3. Fever onset: one has the chills, feeds ‘cold’, clammy to touch, as their body temp is now well below the new set point.
4. Chill phase: shivering (increased metabolic heat) and bv vasoconstriction (reduce heat loss) results in increases metabolic rate - causing body temp to rise. (Increased heart rate also to deliver WBCs to infection sites).
5. Crisis point: when the fever ‘breaks’ - where pathogens now destroyed/ infection subsides, the thermostat reduces down to normal 36.8.C. (heat losing mechanisms activated) so the person now feels hot - sweating and skin vasodilation to increase heat loss. Person’s skin to warm and has hot flushes.
pyrogen
A fever producing substance (or pathogen releases toxins)
benefits of fever
1. Inhibit the growth/destroys pathogen
2. Inhibits viral replication - allows chemicals called interferons to operate more quickly.
3. Increased heart rate/blood flow: enables WBCs to reach site of infection faster.
4. Heat speeds the rate of chemical reactions -> promotes healing/ tissue repair.
Interferons
are proteins secreted by cells that have been invaded by viruses.
They alert other cells to make antiviral proteins
Consequences of fever
too high fever -> denaturing of proteins.
Convulsions, brain damage, loss of consciousness, coma, death.
lymphatic system function
1. To collect fluid that escapes from the blood capillaries and returns it to circulatory system
2. Important role in body’s internal defence against pathogens - helps immune system
3. Transports dietary fats
Lymphatic system components
network of bind ended lymph capillaries join to larger lymphatic vessels (have valves).'
Lymph nodes containing lymphoid tissue with macrophages and lymphocytes - filters fluid before returned.
cris-crossed network of fibres in nodes, micro-organisms get trapped, macrophages ingest + destroy by phagocytosis.
Lymph fluid originates from tissue - contains cell debris, foreign particles + pathogenic micro-organisms.
Lymphatic system organs
1. tonsils
2. adenoids
3. spleen
4. thymus
5. Bone marrow
Infections of the body occur when:
1. Lymphocyte number increases
2. Lymph nodes become swollen and painful to touch
