1.1 Reflex actions are rapid and happen without us thinking. For
example, you would pull your hand away from a hot flame
without thinking about it.
1.1.1 This is what happens: receptor detects a stimulus - change
in the environment sensory neurone sends signal to relay
neurone motor neurone sends signal to effector effector
produces a response
188.8.131.52 light is also a reflex action. In bright light: Less light enters the
eye through the contracted pupil. In dim light:More light enters
the eye through the dilated pupil.
1.2 When a receptor is stimulated, it sends a signal to the
central nervous system, where the brain co-ordinates the
response. But sometimes a very quick response is needed,
one that does not need the involvement of the brain. This is
a reflex action.
2 Central Nervous System
2.1 (the brain and spinal cord) connected
to body by sensory & motor neurons=
peripheral nervous system (PNS)
2.1.1 PNS is 2nd major division of
184.108.40.206 its sensory+motor neuron transmit
messages all over body+transmit
messages to and from CNS
2.2 the most important part of nervous system. if you break your
spine, you become paralysed. if you damage your brain you can die.
the CNS causes reverse movements. the PNS senses change in the
environment + this changes in the bone.
2.3 Sensory neurons carry impulses from receptors to the CNS.
2.3.1 Motor neurons carry impulses from the CNS to effectors.
220.127.116.11 Sensory and motor neurons form part of the peripheral nervous system.
3 behaviour voluntary and invouluntary
3.1 simple reflexes in humans
3.1.1 stepping: this supports
evolution because in past babies used
to walk with their families
18.104.22.168 gripping: babies used to hold on to
22.214.171.124.1 startled: loud noises make babies reach
out for accomplice
126.96.36.199.1.1 grasping: babies tightly grasp a finger
that is placed in their hands
188.8.131.52.1.1.1 rooting: touching the cheek makes
babies turn towards the breast
184.108.40.206.220.127.116.11 sucking: babies suck on a finger or
mothers nipple that is put in its mouth
3.2 simple reflexes are called involuntary: we cant
help doing some movements e.g. sneezing
4 receptors and effectors
4.1 lens: focus the light on retina
4.1.1 retina: contains sensitive
18.104.22.168 optic nerve: sends electrical
signals called impulses to brain
22.214.171.124 retina: senses light+colour,
receptor cells sends info to
4.2 Effectors = any part of the body that produces the
response.some examples of effectors: a muscle
contracting to move the arm. a muscle squeezing
saliva from the salivary gland. a gland releasing a
hormone into the blood.
4.3 Receptors are groups of specialised cells. - detect changes in the
environment, - called stimuli, + turn them into electrical
impulses. Receptors often located in sense organs, such as the
ear, eye + skin. Each organ has receptors sensitive to particular kinds of
5.1 memory and learning
5.1.1 Short-term memory lasts for about 30 seconds.
This is why, when you look up a new telephone
number, by the time the call has ended you have
forgotten the number.
126.96.36.199 Long-term memory may last for the whole of your life. When you
sing the words of a favourite song, you are using your long-term
memory. Although we often complain about how hard it is to learn
new things, there is no limit to how much information you can store
in your long-term memory.
5.1.2 Memory is improved through repetition. If we repeat
things, especially over a long period of time, we are much
more likely to remember them using our long-term memory
188.8.131.52 A strong stimulus - including colour, light, smell or sound -
also helps us to remember things.
184.108.40.206.1 We are more likely to remember information if we can
either see or make a pattern out of it.
5.2 The cerebral cortex is the part of the brain
responsible for intelligence, language,
memory and consciousness.
5.2.1 Scientists have stimulated different
parts of the brain with a weak electrical current then
asked patients to describe what they experienced. If the
motor area is stimulated, the patient makes an involuntary
movement. If the visual area is stimulated, they may see a
flash of colour.
5.3 There are billions of neurons in the human brain
5.3.1 Learning occurs when humans interact with their environment. This causes more neural pathways
to be formed in the brain.
220.127.116.11 Learning results in these neural pathways being used more than other neural pathways
18.104.22.168.1 An example of a skill that can only be acquired at a certain age is learning language for the first time.
6 our nervous system and drugs
6.1 Some drugs and toxins affect how impulses pass from one
neuron to the next across a synapse.
6.1.1 curare (a drug) stop the impulse from passing across the
synapse.They cause complete paralysis/ stop the person from
22.214.171.124 Other drugs stimulate the synapse so that once an impulse crosses
the gap the impulse is repeated over and over again. Drugs such as
strychnine do this. They cause all the muscles in the body to go into
a continuous spasm of constriction. This also stops the person from
126.96.36.199.1 Strychnine is used by Australian aborigines to paralyze fish
188.8.131.52.1.1 Serotonin is a chemical that is released into synapses in the
brain. An increase in serotonin makes us feel happier.
184.108.40.206.1.1.1 Ecstasy is a drug that blocks the serotonin in the synapses in
brain. This prevents the serotonin from being absorbed by the
receptor molecules.=level of serotonin in the synapse
increases.= a feeling of happiness. However, the use of Ecstasy
reduces memory. can also cause severe dehydration= death.
6.2 Curare can cause complete paralysis.
6.2.1 Strychnine can cause a continuous spasm.
220.127.116.11 Ecstasy works by blocking the sites in the
brain's synapses where serotonin is removed.
18.104.22.168.1 The mood-enhancing effects of Ecstasy are due
to an increase in serotonin concentration.
7 conditional response
7.1 it is when you learn something and remember it.
7.1.1 e.g. pavlov+dog
22.214.171.124 Show dog food --> Dog drools (reflex action) Ring bell, show dog food
--> Dog drools (If you continue this, ringing the bell before food
repeatedly you get: Ring Bell ---> Dog drools (conditioned reflex action)
7.2 conditioned reflex
7.2.1 Conditioned reflexes are useful because they increase an animal’s
chances of survival.
126.96.36.199 e.g. birds will not eat caterpillars with bright colouring because they are conditioned to
think of bright colours as poisonous. Some caterpillars use this to their advantage. Their bright
colours protect them, even though they are not poisonous.
188.8.131.52.1 a hoverfly mimics a wasp with its black and yellow stripe, the birds will not eat it because they dont
want to be stung. this helps the hoverfly to survive
7.2.2 A conditioned reflex has no direct
connection to the stimulus
7.3 In some circumstances the brain can modify a reflex response. It does
this by sending an impulse along a motor neuron of the reflex arc. This enables us, for example, to
hold onto a hot dinner plate when normally we would drop it.
8 feral children
8.1 isolated from society
8.1.1 in a cellar or locked room
184.108.40.206 dont have the ability to talk, instead they grunt noises
8.2 these are children who do not learn a language
9.1 reflex arc
9.1.1 The best description of the pathway of a reflex arc is: receptor - sensory neuron - spinal cord - motor
neuron - effector
9.1.2 The brain can modify a reflex arc via the motor neuron of the reflex arc.
9.2.1 sensory neurons carry signals from receptors to
the spinal cord and brain. relay neurones carry
messages from one part of the CNS to another.
motor neurones carry signals from the CNS to
220.127.116.11 The axon is surrounded by a fatty layer known
as the myelin sheath. This helps to protect the
neuron and allow impulses to travel faster.
9.3 The fatty sheath does not connect two neurons together
9.3.1 Chemicals are released into the synapse at
the end of a sensory neuron.
18.104.22.168 chemicals that are released by a sensory neuron into a
synapse when they reach a motor neuron bind with
22.214.171.124.1 Receptor molecules only bind with specific chemicals
126.96.36.199.1.1 After a chemical released from a sensory neuron binds
with a receptor molecule, a nerve impulse is initiated
10.1 gaps between neurons.
10.1.1 how do synapse work?
10.1.1.1 impulse comes down, serotonim is
quickly given off. serotonim diffuses+fills
receptors. when receptors are filled the
excess serotonim are reabsorbed into
the first neuron. this triggers an
electrical impulse in the second neuron.