B3 - Infection And Response Flashcards
What is a communicable disease?
A disease that can spread from person to person.
What is a pathogen?
What are the 4 types of pathogens?
A microorganism that causes disease.
All pathogens have antigens (which have a specific shape) on their surface.
4 types of pathogens:
- bacteria
- viruses
- protists
- fungi
What is bacteria?
Prokaryotic (no nucleus)
Very small - 1/100th of human cells
Produce toxins
Toxins = chemicals produced by pathogens that make us feel poorly
What are viruses?
Not cells & not living
Very tiny - 1/100th of bacteria cells
Enter body cells and reproduce
What are protists?
Eukaryotic (have nucleus)
Single celled
E.g. parasites
What is fungi?
Eukaryotic
Can be both single celled or multicellular
Have hyphae (thread like structures that can penetrate human skin)
How are pathogens spread? Examples?
- through water - e.g. cholera (bacteria)
- through air: breathing in droplets of cough/sneeze - e.g. flu (virus)
- through direct contact: touching surfaces - e.g. athletes foot (fungus)
How to reduce / prevent the spread of pathogens? (Non-specific response)
- hygiene (e.g. wash hands)
- destroy vectors (e.g. insecticides)
- isolate infected individuals (quarantine)
- vaccination (cannot develop infection)
How does the body prevent pathogens from entering?
- skin = barrier
traps particles:
• hair (nostrils, lashes, etc)
• wax
• mucus
- hydrochloric acid = kills pathogens
- vagina = acidic (hostile environment)
- tears = wash eyeball
What type of disease is measles?
Symptoms? & Spread by?
Pathogen: virus
Symptoms:
• fever
• red skin rash
Spread by: inhalation of droplets from sneezes or coughs
What type of disease is HIV?
Symptoms? & Spread by?
Pathogen: virus
Symptoms:
• flu like illness
• attacks the body’s immune system (if it is not treated with antiviral drugs)
• in late stage hiv - the body cannot deal with infections or cancer
Spread by: sexual contact & bodily fluids (e.g. blood)
What type of disease is tobacco mosaic virus?
Symptoms? & Spread by?
Pathogen: virus
Symptoms:
• mosaic pattern of discolouration on the leaves (chloroplasts are infected)
• decreases photosynthesis which reduces growth
Spread by: direct contact
What type of disease is rose black spot?
Symptoms? & Spread by?
Pathogen: fungus
Symptoms:
• purple or black spots on leaves
• leaves can turn yellow and drop off
• less chlorophyll for photosynthesis = less energy
Spread by: spores from fungus are spread by wind or water
What type of disease is malaria?
Symptoms? & Spread by?
Pathogen: protist
Symptoms:
• recurrent fever
• shaking when protists burst out of red blood cells
Spread by: mosquito vector
What type of disease is salmonella?
Symptoms? & Spread by?
Pathogen: bacteria
Symptoms:
• fever
• stomach cramps
• vomiting
• diarrhoea
Spread by: contaminated food
What type of disease is gonorrhoea?
Symptoms? & Spread by?
Pathogen: bacteria
Symptoms:
• (in early stages) - thick yellow/green discharge from vagina or penis
• pain when urinating
Spread by: sexual contact
How does your immune system respond to pathogens?
If a pathogen enters your body, your immune system can attack it.
The main part of your immune system are your white blood cells.
What are the 3 main purposes of white blood cells?
1) Phagocytosis: foreign cells are engulfed and digested
2) Produce antitoxins
3) Produce antibodies
What are antibodies?
White blood cells produce antibodies to fit onto the antigen.
The pathogens are destroyed by other white blood cells.
Antibodies (proteins) are then produced rapidly and are carried around the body in the blood to find other pathogens.
If a person is infected with the same pathogen, the white blood cells quickly produce the antibodies and you don’t feel poorly. (This is natural immunity)
What is a vaccine?
How do vaccines work?
A small amount of dead or inactive pathogen that is injected into your body.
- The pathogen carries antigens
- Your body produces antibodies to attack the antigens
- If you then catch the disease your white blood cells rapidly produce lots of antibodies
What are the advantages and disadvantages of vaccines?
Advantages:
• have helped control/eradicate some diseases (e.g. small pox)
• reduce epidemics by slowing the spread of disease
Disadvantages:
• don’t always work
• can cause a bad reaction (e.g. swelling, fever, etc)
What are painkillers?
Painkillers
= treat the symptoms of a disease but do not kill the pathogens (e.g. paracetamol)
What are antibiotics?
Antibiotics
= kill (prevent the growth of) the bacteria causing the problem without killing your own body cells
• Antibiotics break down the cell walls of bacteria.
• They do not kill viruses because they reproduce inside body cells.
E.g. penicillin
The discovery of penicillin:
Who?
When?
How?
Discovered by Alexander Fleming in 1928
• He left some petri dishes that were contaminated with mould
• He found that bacteria would not grow near the mould
Antibiotic resistance = when antibiotics stop killing the bacteria
How does antibiotic resistance happen?
• bacteria can mutate (change)
• this can cause them to be resistant (not killed by) to an antibiotic
• if you have an infection and treat it with antibiotics only the non-resistant bacteria are killed
• the resistant bacteria are not killed, so they can survive and reproduce
This is an example of natural selection (evolution theory by Charles Darwin)
How to reduce antibiotics resistance?
• doctors do not over prescribe antibiotics
• patients should complete the course of antibiotics
Which two examples of drugs that originate from plants do you need to know?
The painkiller Aspirin originates from willow
The heart drug Digitalis originates from foxgloves
What are the 3 factors drugs are tested for?
What makes a good medicine?
Toxicity, Efficacy, & Dose
Effective, safe, stable, & removable
What is the process of a drug trial?
Stage 1: preclinical trials where drugs are tested on human cells and tissues for efficacy and toxicity.
Stage 2: preclinical tests on live animals for efficacy, toxicity, and dose.
Stage 3: clinical trials
1. Low dosage given to healthy human volunteers to identify any side effects
2. Tested on patients with the condition to find optimal dosage and test efficacy
3. Blind and double blind trials using placebos
What is a placebo?
What are double blind trials?
Placebo = a substance that has no active ingredients used as a control in testing new drugs.
Double blind trials = the volunteers and doctors do not know whether the real drug or a placebo is given.
