GCSE AQA Core Biology Revision

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  • Created on: 24-05-11 16:40
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11.1 ­ Body's Response To Change
Nervous System
CNS (Central Nervous System) ­ Brain and spinal cord. Its function is to
receive information from all parts of the body, interpret it and send messages
to other parts of the body telling it what to do.
Neurones (Nerve Cells) ­ Carry information as tiny electrical signals (impulses)
very quickly to and from the CNS. There are 3 different types of neurones:
1. Sensory Neurones ­ Carry information to the receptors in the sense
organs to the CNS.
2. Relay Neurones ­ Carry messages from one part of the CNS to another.
3. Motor Neurones ­ Carry information from the CNS to effectors in
muscles, glands or organs.
Synapses connect neurones:
The nerve signal is transferred by chemicals (neurotransmitters) which
diffuse across the gap.
These chemicals then set off a new electrical impulse in the next
neurone.

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Receptors ­ Groups of specialised cells, which detect changes in the
environment (stimuli) and then turn them into electrical impulses. They are
often located in the sense organs.
Sense Organ Receptors Sensitive To...
Skin Touch, Pressure, Pain and Temperature
Eyes Light
Tongue Chemicals in food
Nose Chemicals in the air
Ears Sound and Position of the head
Effector ­ A muscle, gland or organ capable of responding to a stimulus.…read more

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Gland Hormone Effect
Adrenal Gland Adrenalin Prepares body for action - 'fight or flight'.
Ovary Oestrogen Controls puberty and the menstrual cycle in females;
stimulates production of LH and suppresses the
production of FSH in the pituitary gland.
Ovary Progesterone Maintains the lining of the womb - suppresses FSH
production in the pituitary gland.
Pancreas Insulin Controls blood sugar levels.
Pituitary Anti-Diuretic Controls blood water level by triggering uptake of water
Gland Hormone (ADH) in kidneys.…read more

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There are three main hormones involved with the menstrual cycle:
1) FSH (Follicle Stimulating Hormone):
1) Produced by the pituitary gland
2) Causes an egg to mature in one of the ovaries
3) Stimulates the ovaries to produce oestrogen
2) Oestrogen:
1) Produced by the ovaries
2) Causes pituitary gland to produce LH
3) Inhibits the future release of FSH
3) LH (Luteinising Hormone):
1) Produced by the pituitary gland
2) Stimulates the release of an egg at around the middle of the
menstrual cycle…read more

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Some women have difficulty becoming pregnant because they don't produce
enough FSH to allow their eggs to mature. 'Fertility drugs' contain FSH, which
stimulates eggs to mature in the ovary.
Advantages Disadvantages
1) Helps a lot of women get 1) It doesn't always work ­ some woman may have to
pregnant. do it many times, which is expensive.
2) Too many eggs could be stimulated resulting in
unexpected multiple births.
IVF can also help couples to have children...…read more

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The kidneys will remove the excess from the blood ­ this is then got rid of
in urine.
Water Content
Water is taken into the body as food and drink and lost from the body in
these ways:
1. through the skin as sweat
2. via the lungs in breath
3. via the kidneys as urine
Temperature
The enzymes within the human body work best at 37oC and so this is the
temperature your body tries to maintain.…read more

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­ Healthy Body
Food Group What It's Used For Found In ...…read more

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Fat Rubbing it on paper If when held to the light, paper goes transparent
Metabolic Rate ­ Speed at which chemical reactions take place in the body.
Reasons for variation include:
age
gender - male or female
the proportion of muscle to fat in the body
the amount of exercise and other physical activity
genetic traits
Metabolic rate increases as we exercise and stays high for a while
afterwards.
Cholesterol
Cholesterol is found in the blood.…read more

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­ Drug Abuse
Drug Testing
Placebo ­ A drug that looks identical to the real medicine, but has no medical
benefit.
Blind Trial ­ Volunteers do not know whether they have the new drug or a
placebo. This eliminates psychological factors to help provide a fair
comparison.
Double Blind Trial - Neither volunteer nor doctor know which pill has been
given. This eliminates all bias from the test, as the doctors can't influence the
volunteers in any way.…read more

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Recreational Drugs
Can be legal (e.g. caffeine or tobacco) or illegal (e.g. cocaine)
Illegal drugs are separated into 2 main classes: soft and hard
Reasons for taking recreational drugs are:
Enjoyment, relaxation or stress relief
To get stoned
For inspiration
Medical Drugs
Interfere with your body's chemical reactions for the better.
Depressants
Calm nerves and relax muscles by slowing down normal functioning of
the CNS.
Examples are alcohol and tranquilizers
Statins
Lower cholesterol levels in people with or at risk of cardiovascular
disease.…read more

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