B6.3 Monitoring & Maintaining Health 2 Flashcards
How do scabs form?
- Skin cut and starts to bleed (blood leaks out of body)
- Platelets change blood protein fibrinogen to fibrin, forming a network of fibres in the cut
- Red blood cells are trapped in fibres forming a blood clot
- Clot hardens to form a scab, keeping skin clean + time to heal
(In time scab falls off)
How does the skin prevent microorganisms from entering body?
Physical barrier
- dry, dead outer cells are difficult for microorganisms to penetrate
- sweat glands produce oils that help kill microorganisms
How does acid in stomach prevent microorganisms from entering body?
It kills pathogens present in contaminated food or drink
How does the cilia and mucus in airways prevent microorganisms from entering body?
- sticky mucus traps microorganisms
- cilia moves mucus up throat to be swallowed
How do nasal hairs prevent microorganisms from entering body?
Keep out dust and larger microorganisms
How do tears prevent microorganisms from entering body?
Contain lysozymes (enzymes that destroy bacteria)
What is the immune system’s main form of defence?
White blood cells
What are the two types of white blood cells?
Phagocytes- cells that engulf/ingest microorganisms and then make enzymes that digest the microorganism
Lymphocytes- make antitoxins or antibodies
Antibodies
Proteins that bind to antigens on the surface of microorganisms
—> once bound pathogen can be ingested by a phagocyte cell and destroyed
Non-specific defence
Defences that prevent entry of all microorganisms
Are antibodies specific or non-specific defences + why?
Specific
Each antibody binds to only one type of antigen and therefore only one type of microorganism
(Each time a new type of microorganism enters the body, a different lymphocyte makes a new body to fight it)
What happens after a disease has been successfully removed from the body?
- white blood cells are able to make the same antibodies if an infection occurs again
- the body now has immunity to the disease (antibodies destroy pathogen before they can cause illness again)
What are hybridomas?
A fusion of myelomas (cancer cells) and lymphocytes
What are monoclonal antibodies made from?
Made in a laboratory using hybridomas
Produced by a single clone of cells
What do monoclonal antibodies do?
Designed to target a specific toe of cell
—> (like antibodies produced by white blood cells) bind to antigens of target cell = kills cell or prevents it from operating effectively
How are hybridomas made?
Genetically modified mice are injected with the required antigen
—> bodies produce immune response, producing antibodies to the specific antigen
—> antibody-producing lymphocyte cells are collected which cannot survive outside of the body and are therefore fused with myeloma cells from the bone marrow which reproduce indefinitely
—> fused cells = hybridomas
How are monoclonal antibodies produced from hybridomas?
Hybridomas reproduce to form clones
—> each clone produces required antibody which is harvested
—> the proteins = monoclonal antibodies
How are monoclonal antibodies used in pregnancy testing?
When a woman becomes pregnant she produces hormone hCG (human chorionic gonadotrophin) 2 weeks after conception
—> monoclonal antibodies produced to bind to hCG protein causing a colour-change reaction
—> home pregnancy test = short stick with a band of monoclonal antibodies, when using w hCG contacts antibodies a line appears on the stick
How are monoclonal antibodies used to detect disease?
Some monoclonal antibodies act as markers; by binding to a specific antigen they confirm its presence
—> monoclonal antibodies developed to bind to antigens of prostate cancer cells in men
—> allows early diagnosis which is crucial for successful treatment
How are monoclonal antibodies used in treating cancer?
Monoclonal antibodies target specific cells killing them or preventing them from operating efficiently, as well carrying drugs or radioactive substances directly to a cancer cell
= increases effectiveness of treatment, minimises damage to surrounding tissue
Why do we use vaccines?
Some pathogens can make you seriously ill before your immune system has a chance to respond so it’s better not to get infected at all
How do vaccines work?
-con again small amounts of weakened or dead versions of a pathogen
—> inserted into body usually by injection
—> causes lymphocytes to produce antibodies to pathogen
—> person is immune (if encounters real pathogen body can respond quicker)
Antiseptics
Kill or neutralise all types of pathogen w/o gpdmaging human tissue
—> different antiseptics act on different microorganisms (eg. Bacteria)
Common antiseptics = alcohol, iodine
Antivirals
Drugs that destroy viruses (usually by preventing replication)
—> many antivirals are specific and designed to act on one type of virus
Treat infections, eg. HIV, influenza, herpes, hepatitis B
What can the activity of an antiviral include?
- blocking virus from entering host cell
- preventing virus from releasing genetic material
- preventing virus from inserting genetic data into host cell’s DNA
Antibiotics
Drugs that kill bacteria w/o damaging human cells, no effect on viruses or fungi
-several types of antibiotic, each kills a different range of bacteria
How do doctors identify bacteria making person ill?
- Send stool/blood sample to lab
- Scientists grow bacteria in samples on agar plate
- Treat bacteria w different antibiotics to find most effective
- Person prescribed most effective antibiotic
Zone of inhibition
Area on agar plate that bacteria cannot grow
—> measures effectiveness of antibiotic
How to measure the zone of inhibition
- Measure diameter of zone of inhibition
- Divide diameter by two for radius
- Use pie r^2 to find area
Aseptic technique
An approach to working which prevents cross-contamination from unwanted microorganisms by ensuring apparatus and environment remain sterile
(Aseptic = w/o microorganisms)
What is done to ensure aseptic technique?
- wash areas with alcohol before + after working
- wear gloves if at risk of working with pathogens
- autoclave glassware before + after use
- work close to Bunsen burner flame
How to sterilise a wire loop
- Heat in Bunsen burner flame until red hot
2. Cool before use while holding near flame and away from bench
How can you identify bacteria?
Grow a colony and characteristics such as shale, colour, edge and surface appearance, and elevation allow you to identify bacteria from sample
Technique for isolating bacterial colonies
- Dip sterilised wire loop into sample of bacteria
- Make 4/5 streaks across one edge of an agar plate
- Flame and cool wire loop
- Make new series of streaks by crossing over first set, picking up some of cells and spreading them across a new section of the plate
- Repeat steps 3+4 making third set of streaks
- Repeat steps 3+4 making fourth set of streaks
- Fix lid with four short lengths of tape
- Label and incubate plate upside down for several days. Do not open, dispose in disinfectant or sterilise
Why is the lid secured using short lengths of tape?
Sealing all the way around wouldn’t allow any air to enter
—> anaerobic conditions often promote growth of pathogenic bacteria
Why is agar jelly used?
Nutrients are added to the agar which sets as a jelly = medium for bacteria to grow on
How are new drugs discovered?
- plant extracts
- made in laboratory
- computer modelling (software produces list of compounds that may target a particular condition)
Preclinical testing
When finding a potentially useful substance scientists perform laboratory tests to find out how it behaves
Eg. testing on live cells, bacteria, tissue cultures
BEFORE testing on live organisms
(Most drugs fail at this stage as they damage cells or don’t work)
Stages of testing a drug must undergo
- Drug tested on animals (in UK data needed from 2 animal species before it can be used on humans)
- Clinical trial = drug tested on humans
Stages of a clinical trial
- Tested on healthy volunteers to look for unexpected side effects
- Tested on small sample of volunteers who suffer from condition to see how effective it is
- Drug tested on large number of people with condition to se how well it works and check it is safe for everyone
If all tests are positive who approved drug (in UK)?
MHRA- the Medicines and Healthcare Products Regulatory Agency
Placebo effect
Sometimes people feel better because they expect to feel better when taking medicine
How do clinical trials overcome the placebo effect?
Researchers use a double blind trial =
Some patients are given drug, others get an exact replica of the drug with no active ingredients
—> doctors and patients aren’t told who has received drug until test is over
Animal testing, principle of 3 Rs
Reduction - use smaller number of animals possible
Refinement- improve experiments to avoid unnecessary suffering and improve way animals are cared for
Replacement - where possible replace use of animals with other techniques (eg. using cell cultures or computer models)
