Infection and Response Flashcards
Pathogens
Microorganisms that enter your body and cause disease
What types of disease do pathogens cause
Communicable
What can be infected by pathogens
- animals
- plants
Types of pathogen
- bacteria
- virus
- protist
- fungi
Bacteria
Very small living cells that reproduce rapidly in your body
How do bacteria make you ill
Produce toxins that damage your cells and tissues
Viruses
- live inside your cells
- 1/100 size of bacterium
- reproduce rapidly using cell’s machinery
How do viruses make you ill
- cells full of virus copies burst
- cell damage makes you ill
Protists
Single celled eukaryotes
How do parasite protists cause damage
By living on or inside other organisms
Vector
Something (often an insect) that carries protists to an organism without getting the disease itself
Fungi structure
- some single celled
- some have body made up of hyphae (thread like structures)
How do fungi cause disease
Hyphae grow and penetrate human skin and plant surface causing disease
How can hyphae spread to other plants and animals
By producing spores
How can pathogens be spread
- water
- air
- direct contact
How does water spread pathogens
Some pathogens picked up by drinking or bathing in dirty, contaminated water
How does air spread pathogens
- some pathogens are carried in air and breathed in
- some pathogens are carried in air in droplets produced when you sneeze or cough
How does direct contact spread pathogens
Some pathogens picked up by touching contaminated surfaces, including skin
Viral diseases
- measles
- HIV
- TMV
How is measles spread
Droplets from infected person’s sneezes/coughs
Measles symptoms
- red skin rash
- fever
- can lead to pneumonia
- can lead to encephalitis (brain inflammation)
How is measles prevented
Receive vaccination when young
How is HIV spread
- sexual contact
- exchanging bodily fluids (often when sharing needles when taking drugs)
Effect of HIV
- initially flu-like symptoms for few weeks
- attacks immune cells
- no symptoms for several years
- develops into aids
HIV treatment
Antiretroviral drugs stop virus replicating in body
TMV
Tobacco mosaic disease
Effect of TMV
- mosaic pattern on plant leaves
- discolouration of leaves means plants can’t photosynthesis
Fungal disease
Rose black spot
How does rose black spot spread
- water
- wind
Effect of rose black spot
- purple or black spots on rose plants causing leaves to turn yellow and drop off
- less photosynthesis
How is rose black spot treated
- fungicides
- stripping plants of infected leaves and destroying them so they can’t spread to other plants
Protist disease
Malaria
How is malaria caused
- mosquito vectors pick up malarial protist by feeding on infected animal
- when mosquito feeds on another animal, inserts protist into animals blood vessels
Effect of malaria
- fever
- sometimes death
Malaria prevention
- stop mosquito breeding
- insecticides
- mosquito nets
Bacterial diseases
- salmonella
- gonorrhoea
Salmonella
Type of bacteria which causes food poisoning
Salmonella cause
- eating food contaminated with salmonella bacteria
- eating food prepared in unhygienic conditions
What causes salmonella symptoms
Toxins produced by the bacteria
Salmonella symptoms
- fever
- stomach cramps
- vomiting
- diarrhoea
Salmonella prevention
- most poultry in UK given vaccinations against it
- cook food properly
Gonorrhoea cause
Sexual contact
Gonorrhoea symptoms
- pain when urinating
- yellow/green discharge from vagina/penis
Gonorrhoea prevention
Barrier methods of contraception, like condoms
Gonorrhoea treatment
- originally penicillin, but strains have become resistant
- antibiotics
How to reduce/prevent spread of disease
- being hygienic
- destroying vectors
- isolating infected individuals
- vaccinations
How to be more hygienic to reduce/prevent spread of disease
Washing hands after sneezing to stop infecting another person
How to destroy vectors to reduce/prevent spread of disease
- insecticides can kill insect vectors
- destroy insect vector’s habitats so they can’t breed
How can isolating infected individuals reduce/prevent spread of disease
Isolating people with communicable diseases stop them passing it on
How can vaccinations reduce/prevent spread of disease
Vaccinating against communicable diseases lessens likelihood of developing infection and passing it on
Parts of human body that stop pathogens getting in
- skin
- nose
- trachea and bronchi
How does skin stop pathogens getting in
- acts as barrier
- secretes antimicrobial substances which kill pathogens
How does nose prevent pathogens getting in
Hairs and mucus in nose trap particles that could contain pathogens
How do the trachea and bronchi prevent pathogens getting in
- trachea and bronchi secrete mucus from globlet cells to trap pathogens
- these are lined with cilia which waft mucus up to throat to be swallowed
- stomach produces hydrochloric acid to kill swallowed pathogens
How does the body detect pathogens
White blood cells travel all around the body looking for them
How do white blood cells deal with pathogens
- phagocytosis
- antibodies
- antitoxins
Phagocytosis
- phagocyte binds to pathogen
- phagocyte engulfs pathogen into cell and encloses it
- phagocyte secretes digestive enzymes to break down pathogen
- debris excreted
How do antibodies attack pathogens
- white blood cell detects unique antigens on pathogen surface
- antibodies produced to lock onto invading cells so they can be found and destroyed
- antibodies produced and carried round body to look for similar bacteria/viruses
- if person infected with same pathogen, same antibodies produced, they are immune
B-lymphocytes
White blood cells that produce antibodies
How do antitoxins attack pathogens
They counteract toxins produced by invading bacteria
How do vaccinations work
- inject small, amount of (harmless) dead pathogens carrying antigens
- body produces antibodies to attack them by clumping them together for phagocytes to engulf by phagocytosis, memory cells stay in blood
- if live versions of pathogen enter body, white blood cells can rapidly produce antibodies to kill it before it makes us ill
Advantages of vaccination
- controlled previously common communicable diseases in uk, smallpox gone, polio infections at 99%
- herd immunity - epidemics prevented if large percent of people vaccinated, unvaccinated people less likely to catch it if fewer people have it
Disadvantages of vaccination
- don’t always work
- bad reactions can occur but uncommon
Painkillers
- relieve pain by reducing symptoms
- don’t tackle cause or kill pathogens
Antibiotics
Kill bacteria causing problems without killing your body cells
How do bacteria become resistant to antibiotics
They mutate
How to slow down rate of development of resistant strains of bacteria
Doctors shouldn’t overprescribe antibiotics - only prescribe for more serious diseases
Why do many drugs come from plants
- plants produce chemicals to defend against pests/pathogens
- some of the chemicals can treat human diseases or relieve symptoms
Human medicines developed from plants
- aspirin
- digitalis
Aspirin
Painkiller used to lower fever
What was aspirin developed from
Chemical found in willow
Digitalis
Used to treat heart conditions
What was digitalis developed from
Chemical found in foxglove
How was penicillin discovered
- Alexander Fleming was cleaning Petri dishes containing bacteria
- he noticed one dish had mould on and area around mould had no bacteria
- mould was producing penicillium notatum which killed the bacteria
How are drugs made
- synthesised by chemists in labs
- may come from chemical extracted from plant
Stages of drug development
- preclinical testing on human cells and tissue in lab
- preclinical testing on live animals
- testing on human volunteers in clinical trials
What drugs can’t be tested on human cells and tissues
Ones that affect whole or multiple body systems - must be tested on whole animal
Preclinical testing on live animals
- tests efficacy
- tests toxicity
- find best dosage
- law states a drug must be tested on 2 different live mammals
- some think it’s cruel to test of animals
Efficacy
Whether drug works and produces effect you’re looking for
Dosage
The concentration that should be given and goes often
Testing on human volunteers in clinical trials
- first tested on healthy volunteers to test for harmful side effects when body is working normally
- dosage started off low and gradually increased
- patients randomly put into 2 blind groups, one given placebo to test real drug makes difference and there’s no placebo effect
- results not published until they’ve been through peer review
Placebo
Substance like drug being tested but doesn’t do anything
Placebo effect
When a patient expects treatment to work so feels better, even through treatment isn’t doing anything
