B2 Keeping Healthy MicroorganismsInfectious a disease that can
be caught. The microorganism that causes it is passed from one
person to another through the air, through water, or by
touch.Infections are caused by some microorganisms that invade the
body. Microorganisms are viruses, bacteria, and fungi.When disease
microorganisms get inside the body, they reproduce very quickly.
This causes symptoms the ill feelings you get when you are unwell.
Symptoms of infectious diseases can be caused by:1. Damage done to
your cells when the microorganisms reproduce2. Poisons (toxins)
made by microorganisms. People normally stay fit because: Most
microorganisms do not cause human diseases. Your body has barriers
that keep most microorganisms out.VirusBacteriumFungus
Size20-300 nm1000-5000 nm50 000+nm
Appearance
Examples of diseases causedFlu, polio, common cold, AIDS,
measlesTonsillitis, TB, plague, cystitis Athletes food, thrush,
ringworm
Bacteria can reproduce rapidly inside the body
In ideal conditions in a sealed container bacteria cant keep up
their fastest growth. Food starts to run out, or waste products
kill them off. Lag phase growth gets goingLog phase fastest
increase in growth, bacteria divide every 20 minuteStationary phase
steady phase, growth of new bacteria equals death of old bacteria.
Death phase more bacteria die that are made.
Immune SystemThe parts of the body that fight infections are
called the immune system. White blood cells are an important part
of your immune system. Antibiotics antimicrobial chemicals that
kill bacteria and fungi but not VIRUSES!white blood cellsOne type
of white blood cell makes antibodies (specialised proteins) to
label microorganisms. Some antibodies remain in the blood as
long-lived memory cells, ready to fight again. This means that the
body reacts faster the second time the pathogen returns, the body
destroys the invaders before you become ill - immune to the
disease. A different type digests the pathogen (cause the disease)
-phagocytes. All cells have antigen markers on the outside that are
unique to that type of cell. The antigen markers on microorganisms
are foreign to the body.
A person infected twice by a disease microorganism. Their white
blood cells make antibodies much faster the second
time.Phagocytosis
Summary of the role of white blood cells.
Viruses have high mutation (a change in the DNA of an organism.
It alters a gene and may change the organisms characteristics)
rate. The body will need to make a different antibody to fight a
virus. VaccinationsVaccinations make use of the bodys own defence
system. They kick-start your white blood cells into making
antibodies. So you become immune to a disease without having to
catch it first
Vaccines can improve the health by protecting you from disease.
They are tested to make sure that they are safe to use. But it is
never completely safe because people are genetically different, so
they react differently. Doctors decide that a treatment is safe to
use when: The risk of serious harmful effects is very small The
benefits outweigh any riskTo stop large outbreaks of a disease,
almost everyone in the population must be vaccinated. Why does the
government encourage vaccinations? Almost nobody who has a vaccine
notices any harmful effects Harmful effects from the MMR vaccine
can be mild, or produce a serious allergic reaction Some children
who catch measles are left severely disabled Measles can be
fatalFor society as a whole, vaccination is the best choice. People
often perceive the risk of vaccination to be greater than the risk
of measles. SuperbugsMicroorganisms can be killed by antimicrobial
chemicals. Some only inhibit their reproduction. The persons immune
system destroys those remaining.A tiny change in one gene a
mutation can turn a bacteria cell into a superbug. Just one
superbug wont do much damage. But if it reproduces rapidly, it
could produce a large population of bacteria, all resistant to an
antibiotic.
The risk of antibiotic-resistant superbugs developing increases
if:1. People taking antibiotics they dont really need2. People not
finishing their course of antibiotics. If course is finished, all
bacteria is killed. But if you stop taking the antibiotics because
you feel better, the bacteria that survive will reproduce quickly
because there is no competition for space and food from other
bacteria. How can we stop the superbugs? Create new antibiotics
Have better hygiene in hospitals to reduce the risk of infection
Only prescribe antibiotics when a person really needs them Make
sure people understand why it is important to finish all their
antibiotics (unless side-effects develop)Drug development
StageTestingTo find out
One Drug is tested on human cells grown in the laboratory How
safe the drug is for human cells How well it works against the
disease
TwoDrug is tested on animals If the drug works as well in whole
animals as it does on cells grown in the lab
ThreeDrug is tested on people (human trials or clinical trials)
Gives scientists more data about the effectiveness and safety of
the drug Carried on healthy volunteers checks safety Then tested on
people with the disease to test for safer and effectiveness
Long-term human trials ensure safety (no adverse side-effects) and
that the drug works
Double blind trialsIt is important to be certain that a drug
really does have positive effects, rather than people feeling
better simply because they expect to feel better if they take a
medicine. This is called theplacebo effect.Double blind trials aim
to minimise the placebo effect. Some patients are given the drug
while others are given a placebo (control group). A placebo is
designed to appear exactly the same as the drug itself, but it does
not actually contain any of the drug. The doctors and patients are
not told who have received the drug and who have received the
placebo until the trial is over.Taking placebo would not increase
risk of disease but taking the new drug may bring other risks or
increase chance of getting better. Many doctors do not like giving
a placebo to patients with a disease because they feel the patient
will not benefit from taking a fake drug and will not get better.
They do not think this is fair to the patient.It may seem unfair to
the control group because they may miss benefits of the new drug.
If the trial shows that the risks are too great it will be stopped
If the trial shows that the drug has benefits it will immediately
be offered to the control groupBlind trialsDoctor is told which
patients are being given the drug. This may be because they need to
look very carefully for certain unwanted harmful effects. The
patient does not know.Open-label trialsBoth the patient and doctor
know the treatment. This happens when there is no other treatment
and patients are so ill that doctors are sure they will not recover
from the illness. No placebo. The drug may extend their lifespan or
be a cure!CirculationThe heart is a bag of muscle. The heart is a
double pump, tubes carry the blood around the circulatory system.
How blood circulatesBlood enters the right-hand side of the heart
from the body. It flows into the right lower chamber, which pumps
it to the lungs to pick up oxygen. The blood then flows back into
the upper chamber on the left-hand side of the heart, then into the
left lower chamber. There it is pumped to the rest of the body to
deliver oxygen. There are valves between the upper and lower
chambers to make sure blood flows in the right direction. Heart
AttackBlood brings oxygen and food to cells- makes energy. Without
energy the heart would stop. So heart muscle cells must have their
own blood supply. Sometimes fat can build in the coronary arteries.
A blood clot can form on the fatty lumo. If this blocks an artery,
some heart muscle is starved of oxygen. The cells start to die.
This is an heart attack. Heart dieseas any illness of the heart.
Heart attacks are not normaly caused by an infection. The genes,
lifestyle, or most likely both, affect whether you suffer from a
heart attack. There are may risk factors. The risk increase the
more of these risk factors you are exposed to.
When arteries become clogged up with fatty deposits, it is more
difficult for the blood to be pumped around the body. The heart has
to work harder and will have to beat faster.Pulse rate measure how
hard your heart is working. A more accurate way is taking your
blood pressure (measures the pressure of the blood on the walls of
the artery). Blood pressure is measured in millimeters of
mercury,mmHg. There are two measurements: systolic pressure- the
higher measurement when the heart beats, pushing blood through the
arteries, and diastolic pressure- the lower measurement when the
heart rests between beatsA young, fit person may have a blood
pressure of about 120 over 70, which means their systolic pressure
is 120 mmHg, and their diastolic pressure 70 mmHg.High blood
pressure increases the risk of a heart attack. Narrowing of the
arteries raises heart rate and blood pressure, and so do drugs
(i.e. Ecstasy and cannabis). Lifestyle disease a disease that is
not caused by microorganisms. They are triggered by other factors,
i.e. smoking, lack of exercise, diet etc. It is harder to find the
causes of lifestyle diseases, like heart disease.HOMEOSTASISKeeping
conditions inside the body the same is homeostasis. For example,
keeping the correct levels of water and salt, controlling the
amounts of nutrients and getting rid of waste producs i.e. urea and
carbon dioxide. All control systems have:1. receptor detects the
change (stimuli)2. processing center receives the information and
coordinates response3. effector produces an automatic
responseNegative feedback any change in the system results in an
action that reverses the change. Negative feedback systems reverse
any change to the systems steady state. Changes are coordinated by
both nervous and hormonal communication systems. Water Homeostasis
keeping a steady water level (balancing water inputs and water
outputs).Kidneys have two jobs:1. water homeostasis2. excretion-
getting rid of toxic waste These two jobs are linked because you
need water to flush out all the waste products. Getting the water
level in cells right is important to maintain the correct chemical
concentration levels for cell activity. The concentration of your
blood plasma determines how much water your kidneys reabsorb, and
how much you excrete in urine. The concentration of your blood can
become higher than normal because of: excess sweating because of
increased exercise levels not drinking enough water eating salty
foodThese cases, increase ADH production, kidneys reabsorb more
water, making less urine. DrugsAlcohol suppresses ADH production.
This causes the kidneys to produce a greater volume of dilute
urine. It can lead todehydration causing dizziness, headaches, and
tiredness. Long-term dehydration can have effects on kidneys,
liver, joints, and muscles. Severe dehydration can cause low blood
pressure, seizures, increased heart rate, and loss of
consciousness. Ecstasy increases ADH production. This causes the
kidneys to reabsorb water, reducing the volume of urine. It can
result in the body havingtoo muchwater (causing seizures-fatal,
increase in blood pressure and heart rate, increasing the risk of a
heart attack and brain damage) and affects the bodys temperature
control.
Concentration of blood plasma falls- more waterConcentration of
blood plasma rises- less water
Pituitary gland secretesLess ADHMore ADH
Kidney reabsorbsLessMore
Urine volumeDecreasesIncreases
Urine concentration DecreasesIncreases
Negative Feedback The moreconcentratedthe plasma, the more ADH
is released into the blood. When the ADH reaches the kidneys, it
causes them to reabsorb more water. This keeps more water in the
body and produces concentrated urine. When the plasma is
moredilute, less ADH is released into the bloodstream. This allows
more water to leave the kidneys (kidneys reabsorb less), producing
dilute urine.
Ideas about scienceRepeatsA scientist may take a set of
measurements, or make some observations, and draw conclusions from
them. If the scientist canrepeat this activity, and get similar
data, this provides more evidence to support those conclusions. The
conclusions are therefore more likely to be valid.Peer review
Scientists report their work in scientific journals and at
conferences. Before publication, the work is checked and evaluated
by other experts. This process is known as 'peer review'.When
scientists report their work, other scientists can see what they
have done and try to repeat it. If these other scientists obtain
similar data, it provides more evidence to support the conclusions
that have been published.Scientific findings are only accepted once
they have been evaluated critically by other
scientists.CorrelationCorrelation does not prove a cause and the
outcome might be caused by some other factor, e.g. ice-cream sales
increase as hay fever increases, but ice-cream does no cause hay
fever. Even when evidence exists that a factor is correlated to an
outcome, scientists look for a causal mechanism. E.g. smoking
increases the effect of heart disease because of the effects of
nicotine on the body. Nicotine is the mechanisms.