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Summary ALL of gcse biology content for paper 2
all of gcse biology paper 2 content including Homeostasis and response; Inheritance, variation and evolution; and Ecology
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GCSE BIOLOGY PAPER 2TOPIC HOMEOSTATIS AND RESPONSE
HOMEOSTATIS
Homeostasis is keeping your body in stable internal environment
Cells need certain conditions to function properly
Stimuli – change in environment
Receptors – detects a change, like rise in temp
Co-ordination centre - brain or spinal cord, which interprets the change and decides what needs to be
done
Effectors – carry out the change, like muscles which can contract or glands which release hormones
Negative feedback counter acts a change
If the level of something gets too high, negative feedback decreases it to return it too normal
If negative feedback decreases it too much, it will just increase it back to normal
NERVOUS SYSTEM
The nervous system detects and reacts to the stimuli (change in environment)
The nervous system is made up of:
Central Nervous System (CNS) - brain and spinal cord
Sensory neurone – neurone that carries the impulse from receptors to CNS
Motor neurone – neurone that carries and impulse from CNS to effector
Relay neurone – connects the motor and sensory neurone together.
Effector – what responds to the impulses, muscles and glands
The CNS is a co-ordination centre. It receives info from the receptor and decides what to do with it
, SYNAPSE AND REFLEXES
Synapses connect neurones
The connection between 2 neurones is called a synapse
The signal is transferred via chemicals which moves across the gap
Reflexes help prevent injuries
Reflexes are rapid automatic responses to certain stimuli that don’t involve a conscious part of the brain
e.g., when sun shines in your eyes, the pupils automatically get smaller so fewer light shines in your eyes
reducing a risk of damage
The reflex arc goes through the CNS
The neurones in a reflex arc go through the spinal cord or the unconscious part of the brain
When a stimulus is detected by a receptor, the impulse goes along the sensory neurone to a relay
neurone
INSVESTIGATING REACTION TIME
Reaction time is how quickly you respond to a stimuli
Reaction time can be affected by age, gender or drugs
Caffeine is a drug that speeds up reaction time
To test the effect of caffeine on reaction time, you do this experiment:
The person being tested should sit their arm resting on the edge of a table
Hold ruler vertically between their thumb and forefinger, the zero should be level with their
fingers
Then let go randomly
The person being tested should catch as soon as possible
Measure the number that’s caught behind their thumb
the higher the number, the slower their reaction time is
Repeat several times and calculate the mean distance the ruler fell
After 10 minutes repeat the steps.
Reaction times can be calculated on computers
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