Science Revision



homeostasis is mantaining body temperature to the enviroment.

hypothalamus controls it in the brain.


- sweat , produced by sweat glands which evaporates as it tranfers heat from skin.

- hair erector muscles cuase hairs to lie flat , stop more warm are reaching skin

- blood vessels close to skin surface , more blood flowing near surface to lose more heat.


- not much sweat

- hair erector muscles cause hairs to styand on end to trap warm air near skin.

- blood vessels near skin are narrow so less heat is lost.

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neurones are nerve celss that send info around 

body as electrical impulses.

Dendrons are branches that allow the end of a neurone to connect with other neurones.

Axons are the impulse that travels along it    Synapses are 2 neurones joined together

myelin sheath is an electrical insulator that stops nerve impolse getting lost.

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The nervous system

sence organs detect stimuli

sence organs - eyes , ears , nose , tongue and skin. They contain different receptors ( group of cells that detect stimuli. A stimulus is a change in enviroment. Receptors change stimuli into electrical impulses.

Central nervous system - 

1) a stimulus is detected by receptors

2) information sent to sensory neurones to CNS

3) The CNS is up of the brain and spinal chord 

4) The CNS send info along a motor  neurone to an effector( muscle/ gland) 

5) the effector then responds.

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The nervous system

Eyes - light receptors detect light stimuli

Ears - Sound receptors detect sound stimuli.

Nose - Smell receptors detect chemical stimuli.

Tongue - Tate receptors detect chemical stimuli.

Skin - Receptors detect touch and temperature.

sensory neurone - The nerve cells that carry electrical impulses from receptors to the CNS.

Relay Neurones - The nerve cells in the CNS that carry electrical impulses from sensory nuerones to motor neurones.

Motor neurones - The nerve cells that carry electrical impulses from the CNS to the effectors

Effectors - muscle contract and glands secrete hormones.

( your eyes are sence organs that contains light receptors.

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Reflexes happen without thinking about moving making them quiker than normal.

They help in stoping injury ( pupil get smaller in light to prevent eye damage) 

reflexex are from the receptor to effector and are calles reflex arc.

1 ) bee stings your finger - detected by pain receptors.

2) impulses are sent along a sensory neurone to the CNS.

3) In the CNS , a relay neurone passes on message from sensory neurone to motor neurone

4) Impulses are sent along motor neurone to the effector.

5)  the effector in the muscle contracts to move your hand away from a bee

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Hormones are chemical messages sent in the blood.

endocrine glands produce them , hormones are carried in blood around body then one particular organ responds to the hormone (target organs).

Insulin is a hormone that controls blood sugar levels.

- food contains carbohydrate that puts glucose into the clood

- cells remove glucose from the blood.

BLOOD SUGAR LEVELS TO HIGH ? insulin is added

BLOOD SUGAR LEVEL TO LOW ? insulin is not added

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TYPE 1 Diabetes

TYPE 1 - lack of insulin when pancreas doesnt or doesnt produce enough insulin.

- the perosns blood sugar level can get too high

- to control it is by not eating food that has a lot of sugar or by injecting insluin into blood at meal times. 

EATING A HEALTHY DIET - less insulin injected

DOING REGULAR EXERSISE - less insulin injected

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TYPE 2 Diabetes

person is resistant to insulin

- their body's cells dont respond properly to the hormone.

- blood sugar level can get too high

- can be controlled by eating a healthy diet and getting regular exercise and losing weight.

type 2 and obesity

if you are obese you have a higher risk of getting type 2 diabetes.

you are obese if your body mass index is over 30.

BMI = measured by body mass (kg) over height squared (m )

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Different drugs have different effects on people.

- most are chemical substances that affect the CNS.

- they change people's behavior and are addictive

* Depressants ( alcohol ) slow down activity of the brain

Stimulants (caffiene) increase amount of neurotransmitter at some neurone synapses , they increases the speed of reactions.

Painkiller ( narcotics ) reduce pain , morphine works by blocking nerve impulses in brain.

* Hallucinogens ( LSD) change what a person sees or hears.

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drugs and reactions time

reaction time is how quikly you respond to something.

It can be affected by drugs

measured by ...

- one person holds a ruler between thumb and figer of other person

- they let go

- the other person catches ruler

- measured by how far down the ruler is caught

- the further down , the slower the reactions

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Smoking and Alcohol


tobacco contains carbon monoxide which makes the blood carry less oxygen , Tar which is a chemical that can lead to cancer and nictotine that is addictive.


short term effects of drinking alcohol are slowing of reactions, blurred vision and lower inhibitions. Long term effects of drinking alcohol can cause cirrhosis ( disease in liver ) and brain damage.

Organ transplants

if an organ is very damaged , it can be repllaced with an organ from someone else.

- there is not many organ donors so few people can have a organ transplant

- some people say  people dont deserve an organ transplant if they have harmed it themselves.

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Infectious diseases

infectious diseases are caused by pathogens.

they are spread by ...

WATER - some can be picked up by bathing in or drinking water ( cholera bacteria )

FOOD -  picked up by eating food ( salmonella bacteria )

AIR - airborne pathogens carried in droplets , then other people breathe them ( influenza zirus )

CONTACT - picked up by touching surfaces ( athlete's foot fungus )

BODY FLUIDS - picked up by body fluis like blood ( HIV virus )

ANIMAL VECTORS - animal spread diseases like malaria from mosquito's. 

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Protect against disease


SKIN - very effective , if damaged , blood clots quikly seal cuts and keep microorganisms out.

THE BREATHING SYSTEM -  lined with mucus and cilia , the mucus catches dust and bacteria before reaching lung , the cilia push the gunk-filles mucus away from lungs.


EYES - produce a chemical ( lysozyme ) that kills bacteria on surface of eye.

STOMACH - pathogens in food are killed by hydrochloric acid in stomach.

ANTICEPTICS are used to kill stop disease spreading 

ANTIBIOTICS are used to treat infections - kills bacteria

plants can produce chemicala to defend themselves.

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Antibiotics and Antiseptics investigating

To test them you have to pour hot jelly into a petri- dish

2 ) then when cooled , tranfer bacteria to jelly

3 ) then take 3 paper discs ( 1 - soak in antibiotic 2 - soak in different antibiotic 3 - water)

4 )put lid on and leave for 24 hours at 25 C 

5 ) bacteria will multiply and grow.


clear patches show where bacteria cant grow

the one with the biggest clear ring around is the most effective

control variables- 1) temp

2) size of disc

3 )concentration of antibiotic

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