Communicable diseases Flashcards
what is a pathogen?
disease causing organism
what are the 4 types of pathogens?
bacteria, viruses, fungi, protis
what do pathogens release?
toxins that could endanger us.
what do toxins damage?
our cells
what are the two mechanisms our immune system is divided into?
non specific defence and specific defence
what are the features of non specific defence?
the response is immediate and the same for each pathogen, barriers to entry, phagocytes
what are the features of specific defence?
response is slower and specific to each pathogen, lymphocytes
What are pathogens?
Pathogens are microorganisms that cause infectious disease.
which places in your body are susceptible to pathogen entry?
mouth (oral route, contaminated food or water), nose (inhale droplets. breathing in bacterial droplets), or urogenital openings, or through wounds or bites that breach the skin barrier.
what is a symptom
what the patient is complain of
what is a sign
something that a doctor can see
what is the universal sign of infection?
a fever or temperature
what are the human defence responses?
skin defences, the respiratory system, the digestive system
what does the skin do to defend to against pathogens entering the body?
acts as a barrier, prevents pathogens from reaching the tissues beneath the skin
produces antimicrobial secretions
healthy skin is covered with microorganisms that keep you healthy
what does the respiratory system do to defend you against pathogens entering the body?
your nose is full of hairs and produces mucus
these trap particles in the air that may contain pathogens
the trachea and bronchial secret mucus
the lining of the tubes and covered in cilia
what does the digestive system do to defend you against pathogens entering the body?
the stomach produces acid which kills many pathogens
vomiting /diarrhoea rid the body of pathogens
how does your body defend you against pathogens entering through droplet infections?
The trachea and bronchi have a ciliated epithelium. Cilia are tiny hair-like structures.
Goblet cells in the epithelium produce mucus; mucus traps smaller dust particles and microbes.
Cilia beat together to sweep mucus to the back of the throat, where it is either coughed out or swallowed.
what can you do to prevent pathogen entry/spread of droplet infections?
prevent entry:
coughing up phlegm
spitting phlegm out
prevent spread:
use a paper tissue when sneezing or coughing then put it in the bin
how does your body defend you against pathogens entering through STDs?
the acidic pH of the vagina is not favourable for the growth of most pathogens. The semen of a man is sterile
what can you do to prevent pathogen entry/spread of STDs?
prevent entry:
abstinence
physical barrier eg condom
how does your body defend you against pathogens entering through the skin?
the skin contains may layers of cells, which gives protection.
the top most layer of skin cells is dry and dead, pathogens cannot easily penetrate these dead cells.
sebaceous glands in the skin produce antimicrobial oils to kill pathogens
what can you do to prevent pathogen entry through the skin?
wash hands
wear gloves when operating on patients
how does your body defend you against pathogens entering through food and drink?
the strong acids in the stomach kill any pathogens that may have entered
what can you do to prevent pathogen entry through food and drink?
wash your hands with soap after using the toilet
before you touch or prepare food wash your hands with soap
what do scabs do that prevent pathogens from entering
scabs protect the body by forming a barrier and prevent pathogens entering the body through the site of the injury whilst the skin is healing
what do white blood cells attack?
invading pathogens
what are the 3 things a white blood cell does to defend the body against pathogens?
ingesting pathogens (phagocytes)
producing antibodies
producing antitoxins
what are the two main groups of white blood cells?
phagocytes and lymphocytes
how does ingesting microorganisms protect you against disease?
some wbc ingest pathogens digesting and destroying them, this is called phagocytes
how does producing antibodies protect you against disease?
there is a unique antibody for each pathogen which matches a unique antigen on the surface of each pathogen. once these antibodies have been produced they can be made very quickly if a pathogen enters the body again.
how does producing antitoxins protect you against disease?
antitoxins counteract the toxins released by pathogens
what does a phagocyte do?
engulf and digest pathogens (killing them), killing itself in the process.
what does a lymphocyte do?
produce antibodies and antitoxins.
antitoxins neutralise toxins
what is the first line of defence?
phagocyte
what is the second line of defence?
lymphocyte
how do phagocytes work?
a phagocyte moves towards a bacterium
the phagocyte pushes the sleeve of the cytoplasm outwards to surround the bacterium
the bacterium is now enclosed in a vacuole inside the cell.
it is then engulfed and digested
the bacterium and the phagocyte is killed.
what does a pathogen carry?
a foreign antigen
what triggers an immune response?
a pathogen carrying a foreign antigen
how do phagocytes leave the blood?
squeezing through capillaries to enter tissues that are being attacked
how does lymphocytes antibody reproduction take place?
- Lymphocytes recognise foreign antigens on the pathogens
- The lymphocyte with the matching antibody (shape of antibody matches antigen exactly) clones itself to produce an “army” of cells
- The clone of cells produces the antibody in large quantities
- The antibody binds with the antigen causing clumping of the pathogen
are antibodies specific?
Antibodies are specific – their shape matches exactly the shape of the antigen on the pathogen they are intended for.
what are antigens?
Pathogens that contain certain chemicals that are foreign to the body.
are antibodies proteins?
yes
why does each lymphocyte produce a specific type of antibody
Each lymphocyte produces a specific type of antibody - a protein that has a chemical ‘fit’ to a certain antigen..
Lock and key mechanism
what do lymphocytes produce that destroy pathogens?
Lymphocytes produce chemicals called antibodies that destroy pathogens.
what do antibodies do for phagocytes to ingest them
Antibodies do the following:
cause cell lysis (the pathogens burst)
bind to the pathogens and destroy them
cover the pathogens, sticking them together.
Phagocytes can then ingest them.
what happens if the same type of pathogen enters the body again
lymphocyte cells (memory cells) recognise it and immediately make lots of antibodies. This is immunity: the person is immune to that disease.
why do antitoxins combine with toxins
Antitoxins combine with the toxin to make a safe chemical. Antitoxins are specific to a particular toxin.
how do bacteria reproduce?
Bacteria reproduce by asexual reproduction in any medium, such as food, living tissues or within the blood plasma
what are the stages of bacteria reproduction?
1) DNA is replicated
2) cell elongates
3) cell pinches off in middle
4) daughter cells separate
where do viruses reproduce?
when inside the host cell
where do antibodies work?
in the plasma
can antibodies enter the host cell?
no
because antibodies cannot enter the hoist cell, what does this mean for viral diseases?
prevention is better that a cure for viral diseases
why are vaccines developed?
to prevent the virus from penetrating the host cell
what does vaccination involve?
introducing small quantities of dead or inactive forms of a pathogen or antigen into the body to stimulate the white blood cells to produce antibodies.
This “tricks” the lymphocytes to produce memory cells and antibodies that give lasting immunity
what is the difference between primary and secondary immune response?
During a primary infection levels of antibodies slowly increase, peak at around ten days and then gradually decrease. This is what happens when someone is vaccinated with a dead or inactive pathogen or when someone catches a disease for the very first time. It is called the primary immune response.
A second exposure to the antigen that was in the vaccine, or to the same pathogen that made the person ill before, causes the white blood cells to respond much more quickly this time. This is the secondary immune response. The antibodies are produced so quickly by the memory cells that the pathogen is killed off before it can make the person ill. This is called being immune to a disease or having immunity.
what is immunity?
the ability to withstand disease
what are the two ways immunity is achieved?
active immunity and passive immunity
what is active immunity?
Long lasting immunity
How achieved:
A vaccine with dead or weakened microbes is injected – the body is “tricked” into producing antibodies & memory cells ready for the real thing.
The person gets the disease and his WBCs produce antibodies and memory cells
what is passive immunity?
Short term immunity
How achieved?
1. This is when antibodies are passed on by the mother to the baby during pregnancy.
2. When the antibodies (from another animal/source) are injected into the patient
what kills most bacteria?
penicillin
where do viral diseases reproduce
within the host cell
is it possible to kill a virus in a host cell?
it impossible
what do vaccines prevent
viruses
how do fungal diseases mainly spread?
by contact of the skin with a spore
how are the spores usually carried
wind or water
what does fungi cause
skin diseases
is fungi more lethal to plants or humans?
plants
in what places can fungi grow?
moist places eg, mouth, vagina, penis, in between toes
what is an example of fungal diseases?
athletes foot
fungal infections are …….
itchy
what are protist?
singles celled organisms that cause disease such as plasmodium, that causes malaria
how is the plasmodium parasite carried?
from one victim to another by mosquitoes, which act as a vector
what adaptations do insects have as vectors?
wings means they can travel large distances
what is typhoid fever salmonella typhi caused by?
bacterial disease
what is malaria caused by?
potist
what is measles caused by?
virus
what is HIV/AIDS caused by?
virus
what is rose balck spot caused by?
fungi
what is tobacco Mosaic disease caused by?
virus
what is gonorrhoea caused by?
bacteria
what are antibiotics?
Antibiotics are actually antibodies produced by fungi that kill bacteria
what does there have to be for bacteria to grow?
As long as there is an oxygen and glucose supply for respiration, the bacteria can continue to reproduce and their numbers grow exponentially
where do viruses reproduce?
Viruses reproduce within the host cell
They use their spikes to pierce the host cell and inject their DNA into the host cell
can antibiotics be used to kill viruses?
Antibiotics cannot be used to kill viruses, which live and reproduce inside cells
is it important that specific bacteria should be treated by specific antibiotics
It is important that specific bacteria should be treated by specific antibiotics
what has overdoes of antibiotics led to?
many strains of bacteria, including MRSA (super bug infection)
what are the problems with using antibiotics?
1) Overuse of antibiotics can lead to bacteria becoming resistant (e.g. the MRSA “superbug”). This means that antibiotics must be used sparingly.
2) Antibiotics have no effect on a virus, like the common cold. It is difficult to kill a virus without damaging body tissue. A virus is usually allowed to “run its course”.
what happens when a new resistant stain is formed?
Bacteria exposed to antibiotic
Genetic mutation takes place
The mutation gives resistance (bacteria not killed)
Only those bacteria with the resistance gene survive and reproduce
A new resistant species evolves which CAN’T be killed by antibiotics leading to increased infections and the need to develop new antibiotics
what are some ways to stop antibiotic resistance?
stop overperscribing antibiotics
finish antibiotic course
fund research into new antibiotics that can be used against resistance strains
what do painkillers do?
don’t kill pathogen, treat symptom, doesn’t treat cause of disease, common painkiller drugs treat fever or pain
what are the stages of drug trials?
preclinical trails
potential medicaines are tested on cell cultures, tissue culture ans whole organs
drugs are tested on animals
clinical testing on humans
patients suffering from the disease are tested
What is a placebo?
A placebo is a “dummy” pill that resembles the real pill in appearance but does not
contain the active ingredients.
what are the two types of drug trials?
blind trails
double blind trails
what are the features of blind trials?
Patients do not know which drugs they are taking – a real drug or a “placebo”
what are the features of double blind trials?
Neither the doctors nor the patients know if they are taking the real drug
why do placebos offer a ethical dilemas?
a patient might be sick and still be given a “dummy” pill. Also, you might notice if you had a placebo as you wouldn’t get the side effects of normal drugs…
why are placebos used?
Placebos are generally used to eliminate bias and see if the drug actually works but it does cause potential problems for those suffering from the disease who need the treatment
what are the features of preclinical testing?
Preclinical testing is done in a laboratory using cells, tissues and live animals.
Drugs are tested for
T – toxicity
E – efficacy
D - dosage
what are the features of clinical testing?
Clinical trials use healthy volunteers and patients.
Very low doses of the drug are given at the start of the clinical trial.
• If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug
• In double blind trials, some patients are given a placebo.
