Transcript Biology 1 - The New Bridge Academy

28/03/2016
Biology
(AQA)
New Bridge Academy Science dept.
The Nervous System
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The NERVOUS SYSTEM enables us to react to our
surroundings. It consists mainly of the brain, the spinal chord,
nerve cells (“neurones”) and receptors.
Types of receptor:
1) Light receptors in the eyes
2) Sound receptors in the ears
3) Taste receptors on the tongue
4) Smell receptors in the nose
5) Touch, pressure and temperature receptors in the skin
6) Changes of position receptors in the ears (balance)
Nervous Reactions
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When we react to a stimulus our bodies use the following
pattern:
Stimulus
Receptor
For example, consider a
man and a camel:
Coordinator
Effector
Response
Oh
No!
What are the stimulus, receptor, coordinator, effector and
response in this situation?
Examples of reactions
Stimulus
Bright light
Sour taste
Losing balance
Sit on a drawing
pin
Receptor
(i.e. the thing
that detects the
stimulus)
Effector
(i.e. the thing
that will do the
reaction)
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Response
(i.e. action
taken)
Types of nerve cell
Nucleus
Cell body
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Muscle strands
(effector)
Nerve cells (neurones) are elongated with branched
endings to connect to many muscles fibres.
1) Motor neurone
2) Sensory neurone
Impulse
Impulse
3) Relay neurone
Conscious actions
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A conscious action is one where the brain makes a considered response.
Here’s what happens:
4) The brain
3) Here another sensory neurone
decides to move
carries the signal to the brain
away the hand
5) This impulse is
sent by MOTOR
NEURONES to the
hand muscles (the
effectors) via the
spinal chord…
2) The impulse is carried
by SENSORY NEURONES
to the spinal chord
1) Receptors in
your skin detect
a stimulus
Stimulus
6) Which then
moves the hand
away
Receptor
Motor Neurone
Sensory Neurone
Effector
Coordinator
Response
Reflex actions
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Sometimes conscious action is too slow to prevent harm, e.g…
In situations like this
the body bypasses the
brain to produce a
quicker response.
Here’s how it works…
Reflex actions
2. Sensory
neurone
1. Receptor
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3. Relay
neurone in the
spinal chord
4. Motor
neurone
5. Effector
Synapses
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Neurones never ____ each other – there is a small gap
between them called a _____. A signal is sent from one
_______ to the next by a _______ transmitter across
the synapse. These transmitters are then ________.
Words – chemical, synapse, neurone, touch, destroyed
Homeostasis
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Homeostasis means “controlling internal conditions”:
Waste products that need to be removed + how
CO2
Produced by respiration, removed via lungs
Urea
Produced by liver breaking down amino acids,
removed by kidneys and transferred to bladder
Internal conditions that need controlling + how
Temperature
Increased by shivering, lost by sweating
Ion content
Increased by eating, lost by sweating + urine
Water content
Increased by drinking, lost by sweating + urine
Blood glucose
Increased and decreased by hormones
Fertility
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The amount of glucose in our blood is an example of a process
controlled by hormones. Hormones are “chemical
messengers”, produced by glands and tranposrted by blood.
Another example of a process controlled by hormones is the
menstrual cycle, where hormones can...
1) …stimulate the release of eggs
2) …inhibit the release of eggs
In normal circumstances natural
hormones are responsible for releasing
the egg and for thickening the lining of
the womb. These hormones are
produced by the pituitary gland in the
brain and in the ovaries.
Fertility
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3 hormones are involved in the menstrual cycle: oestrogen, LH and FSH.
Here’s how:
Step 1: FSH
produced by the
pituitary gland
causes both an egg
to mature and the
ovaries to start
producing oestrogen
Step 2: The rising levels of
oestrogen cause the pituitary
gland to stop producing FSH
and produce LH instead
Step 3: LH
stimulates the
release of the
mature egg in
the middle of
the menstrual
cycle
Artificial fertility:
1) To INCREASE fertility FSH is given to stimulate maturation of eggs.
2) To DECREASE fertility oestrogen is given (“The Pill”) to inhibit FSH
production stopping eggs from maturing.
Balanced diet
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A balanced diet should contain fats, proteins and
carbohydrates in roughly these amounts:
Carbohydrates
Fat
Protein
It should also contain water, vitamins, minerals and fibre.
Poor diets
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If we don’t have a balanced diet we may suffer form a
“deficiency symptom”:
Lack of…
Causes…
Vitamin D
Anaemia
Protein
Scurvy (bleeding gums and joints)
Vitamin C
Weak bones and teeth
Vitamin A
Wasting of body tissue
Iron
Rickets
Calcium
Poor night vision
Metabolic Rate and health
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The rate at which our bodies carry out chemical reactions is
called the “metabolic rate”. This rate varies with:
• The amount of work we do
• The amount of fat in our body
• Inherited factors
Condition
Lack of exercise
Fatty diets
Warm weather
Using cars instead of walking
Playing XBox instead of
football
How this affects our health
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Conditions caused by increased weight
Obesity is a condition caused by excess weight. This can also
lead to the following diseases:
Athiritis
Heart disease
What is it?
What is it?
What causes it?
What causes it?
Diabetes
High blood pressure
What is it?
What is it?
What causes it?
What causes it?
Heart disease
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Cholesterol
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Cholesterol is a fatty substance made in the liver from
saturated fats in your food. The amount of it in your blood
depends on your diet and inherited factors.
Cholesterol is transported in the bloodstream attached to
proteins. This combination is called a “lipoprotein”:
Low density lipoproteins
(LDL)
High density lipoproteins
(HDL)
• “Bad” lipoproteins
• “Good” lipoproteins
• Carry cholesterol to cells
• Carry cholesterol back to
liver
• High levels of LDLs cause fat
to build up in the artery
• Helps prevent cholesterol
building up
Restoring the balance
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Saturated fats (“bad fats”) increase cholesterol levels.
Mono-unsaturated fats and polyunsaturates may help reduce
cholesterol and restore the balance between LDLs and HDLs.
Modern diets and health problems
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% obesity in the UK
Drugs
Why do people use
illegal drugs?
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Cannabis: Pros and cons
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In January 2004 cannabis was changed from a class B drug to
a class C drug. Some people think that Cannabis should be
made legal. What are the pros and cons of cannabis?
Pros:
Cons:
Smoking
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Cigarettes contain 3 harmful things:
1. NICOTINE, which is an ___________ drug that raises the
heart beat, narrows the arteries and so causes ____
_____ _____. This leads to heart _________.
2. TAR, which coats the lining of the _______ making them
less able to take in oxygen. It also contains carcinogens
which cause ______________.
3. CARBON MONOXIDE, which is a _______ ____ which
joins up with ____ blood cells making them incapable of
transporting _____________ around the body. In
pregnant women it can cause oxygen deprivation, leading to
low birth ______.
Words – high blood pressure, oxygen, red, addictive,
disease, poisonous gas, lungs, cancer, mass
Tobacco and Lung Cancer
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Smoking has existed in Western
culture since the 16th Century.
However, scientists only proved the
link between it and various diseases
shortly after the Second World War.
Over 50 years I proved the link between
smoking and lung cancer. I published my first
findings in 1950, based on patients in London
hospitals, and then studied 40,000 doctors and
proved a link in a paper published in 1954.
Sir Richard
Doll, 1912-2005
Stopping smoking
There are generally two methods of stopping smoking:
“Cold turkey” – stopping completely with no help
Nicotine Replacement Therapy – e.g. Patches, gum etc
What are the advantages and
disadvantages of each?
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Developing new drugs
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Before a new drug can be approved it has to go through a
strict testing process. Consider the example of thalidomide:
Date
Event
Mid 1950s
Animal testing using thalidomide was undertaken.
Tests showed that it was safe but the tests were
“inadequate” – no tests were done on pregnant animals
Late 1950s
Thalidomide prescribed to pregnant mothers to help
sleep and morning sickness problems
Early 1960s
Babies are born with birth defects and the drug was
banned worldwide. Around 12,000 deformed
Thalidomide babies born, 4,000 die in first year.
Mid 1960s
Tests show that Thalidomide can help leprosy
sufferers and it is still used today for this purpose.
Thalidomide children
Mat Fraser,
comedian and actor
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Tony Melendez,
guitarist
Drugs Research Project
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Explain and give examples for the following:
1) Why do people use legal drugs?
2) What are the drawbacks of legal drugs?
3) Alchohol is a legal drug. What does it do to the human
body?
4) Why do people use illegal drugs?
5) What are the drawbacks of illegal drugs? What can they
cause?
6) Choose one drug and discuss how it affects the human body
Microbes
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Microbes are micro organisms that can cause diseases. They
can enter the body in a number of ways:
They can be
breathed in
through the
mouth or nose
…or other
natural
openings…
They can enter
through cuts or
bites in the skin
Disease
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A disease is any condition where the body isn’t working as it should. This
could be caused by a malfunction in the body (as with diabetes) or it could
be caused by a type of PATHOGEN (a microbe that causes disease):
Bacteria
Viruses
• 1/1000th mm big
• 1/1,000,000th mm big
• Living cells (some are harmless)
• Genetic info inside a protein coat
• Grow very quickly
• Not affected by antibiotics
• Affected by antibiotics
• Release poisons
• Examples: food poisoning,
tetanus, sore throats
• Examples: colds, flu, polio,
chicken pox
Microbes: our defence against them
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Our bodies have four major defence mechanisms against
invading microbes:
The skin acts
as a barrier
If our skin is
cut platelets
seal the wound
by clotting
The breathing
organs produce
mucus to cover the
lining of these
organs and trap the
microbes
Our blood contains
white blood cells
Fighting disease
If microbes enter our body they need to be
neutralised or killed. This is done by
WHITE BLOOD CELLS:
White blood cells do 3 things:
1) They eat the microbe
2) They produce antibodies to
neutralise the microbe
3) The produce antitoxins to
neutralise the poisons produced
by microbes
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Producing antibodies
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You’re going
down
Step 1: The white blood cell “sees”
the pathogen (microbe)
Step 2: The cell produces
antibodies to “fit” the pathogen
Step 3: The antibodies fit onto the
pathogens and cause them to “clump”
Step 4: The pathogens are
“eaten” by the white blood cells
Fighting disease
NATURAL IMMUNITY
This is when antibodies are produced by a
person when needed or they are passed on by
the mother during pregnancy.
ARTIFICIAL IMMUNITY
Can be done in two ways:
1) A vaccine with dead microbes is injected
– the body is “tricked” into producing
antibodies ready for the real thing. This
is called PASSIVE IMMUNISATION
2) The antibodies are injected directly into
the body – this is called ACTIVE
IMMUNISATION.
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Using Antibiotics
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Antibiotics can be used to kill bacteria. However, there are
two problems:
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”.
A smaller example…
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Although vaccinations and antibiotics are useful in the fight
against pathogens, bacteria and virii can mutate to form a new,
resistant “strain”:
Bacteria
1) Variation – some strains of bacteria
are resistant and some aren’t.
2) Competition – The non-resistant
bacteria are killed by the penicillin.
3) Survival of the fittest – the
resistant bacteria survive.
Penicillin
4) Passing on of genes – the resistant
bacteria reproduce and pass on
their adaptations to their
offspring. This is how the bird flu
virus developed.
Using Painkillers
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Painkillers are drugs used to relieve the symptoms of disease
but without killin the pathogens, for example:
Aspirin
Paracetamol
Ibuprofen
The spread of infection
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Guten tag. In the mid-19th century I realised
that many deaths in hospitals could be avoided by
insisting on clean hands and equipment. As a
result of my work deaths in my wards fell from
12% to 1%.
Ignaz Semmelweiss
1818-1865
More people die due to infections from
hospitals than on the roads in Britain.
Hospitals have been trying to improve
hygiene standards:
Year
Amount of hand wash
solution used (litres per
1000 patient days)
MRSA infections per
100 patients
1993
3.5
0.50
1995
6.9
0.48
1997
10.9
0.25
Vaccinations
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Some people argue that the MMR vaccine is a good idea,
others think it is a bad idea. Briefly summarise each side of
the argument:
For
Against
MMR vaccine