Brain and Mind Brain and Mind RevisionRevision

Stimuli and ResponsesStimuli and Responses

In order to survive organisms need In order to survive organisms need to monitor and respond to changes to monitor and respond to changes in the environment.in the environment.

A stimulus is any change in the A stimulus is any change in the environment.environment.

Animals move towards food and Animals move towards food and away from toxins.away from toxins.

Plants grow towards light and Plants grow towards light and water and are affected by gravity.water and are affected by gravity.

Receptors and Receptors and EffectorsEffectors Receptors receive stimuli.Receptors receive stimuli. Effectors bring about a reaction.Effectors bring about a reaction. Receptors can form part of Receptors can form part of

complex organs such as the retina complex organs such as the retina of the eye.of the eye.

Effectors can also form complex Effectors can also form complex organs such as a hormone organs such as a hormone secreting gland or a muscle.secreting gland or a muscle.

Central Nervous Central Nervous SystemSystem

Coordination of Coordination of responses is responses is through neurones through neurones linking receptors linking receptors and effectors via a and effectors via a central nervous central nervous system.system.

NeuronesNeurones Neurones are cells where the cytoplasm Neurones are cells where the cytoplasm

forms fibres covered in a membrane called forms fibres covered in a membrane called an axon.an axon.

Some axons are covered in fatty sheaths Some axons are covered in fatty sheaths which insulate and speed up impulses.which insulate and speed up impulses.

SynapsesSynapses

Receptor cells send impulses along Receptor cells send impulses along sensory neurones to the CNS.sensory neurones to the CNS.

There are gaps between neurones called There are gaps between neurones called synapses.synapses.

When impulses reach the end of sensory When impulses reach the end of sensory neurones chemicals are produced that neurones chemicals are produced that diffuse across the synapse and bind to diffuse across the synapse and bind to receptors on the motor neurone.receptors on the motor neurone.

This causes the motor neurone to This causes the motor neurone to produce a new impulse.produce a new impulse.

SynapsesSynapses

Drugs and SynapsesDrugs and Synapses

Some drugs affect the transmission of Some drugs affect the transmission of impulses across synapses.impulses across synapses.

Drugs such as Ecstasy and Prozac prevent Drugs such as Ecstasy and Prozac prevent the re-uptake of serotonin by blocking re-the re-uptake of serotonin by blocking re-uptake channels in the sensory neurone uptake channels in the sensory neurone leading to a feeling of well being.leading to a feeling of well being.

Toxins such as curare block the receptors Toxins such as curare block the receptors on the motor neurone and prevent on the motor neurone and prevent transmissions of the impulse across the transmissions of the impulse across the synapse causing paralysis.synapse causing paralysis.

Simple ReflexesSimple Reflexes

Reflex arcs produce rapid involuntary Reflex arcs produce rapid involuntary responses called reflexes.responses called reflexes.

Simple animals rely on reflexes for the Simple animals rely on reflexes for the majority of responses.majority of responses.

These reflexes enable the animal to These reflexes enable the animal to respond to food, predators, mates etc.respond to food, predators, mates etc.

The disadvantage of such responses The disadvantage of such responses is that they stop the animal is that they stop the animal responding to new situations.responding to new situations.

Reflex ArcsReflex Arcs

Receptor

Sensory Neurone

Synapse

Motor Neurone

Effector

Conditioned ReflexConditioned Reflex

A new response can be learned by A new response can be learned by associating a secondary stimulus with associating a secondary stimulus with a primary stimulus.a primary stimulus.

Pavlov got dogs to associate a bell Pavlov got dogs to associate a bell ringing with food.ringing with food.

The dogs then salivated when the bell The dogs then salivated when the bell rang.rang.

The secondary response is nothing to The secondary response is nothing to do with the primary response. do with the primary response.

Conditioned ReflexesConditioned Reflexes

Conditioned reflexes provide Conditioned reflexes provide advantagesadvantages

eg a bird will avoid colourful caterpillars eg a bird will avoid colourful caterpillars that have an unpleasant taste.that have an unpleasant taste.

The brain can adapt reflexes in certain The brain can adapt reflexes in certain situations eg holding on to a hot plate.situations eg holding on to a hot plate.

This provides the ability to adapt to This provides the ability to adapt to new situations.new situations.

LearningLearning

Mammals have large brains with billions of Mammals have large brains with billions of neurones.neurones.

Learning is the formation of neurone Learning is the formation of neurone pathways.pathways.

The large number of potential pathways The large number of potential pathways provides the ability to adapt.provides the ability to adapt.

Strengthening pathways by repetitions Strengthening pathways by repetitions helps develop learning.helps develop learning.

Certain pathways only develop at certain Certain pathways only develop at certain ages, eg learning speech in young children.ages, eg learning speech in young children.

The BrainThe Brain

The cerebral cortex is the part of the The cerebral cortex is the part of the brain associated with memory, brain associated with memory, intelligence, language and intelligence, language and conciousness.conciousness.

Three main methods have been used Three main methods have been used to map the areas of the brain.to map the areas of the brain.– Patients with brain damagePatients with brain damage– Electrical stimulation of parts of the brainElectrical stimulation of parts of the brain– Magnetic Resonance Imaging (MRI)Magnetic Resonance Imaging (MRI)

MemoryMemory

Memory can be divided into short-Memory can be divided into short-term and long-term.term and long-term.

Humans remember information ifHumans remember information if– There is a pattern.There is a pattern.– There is repetition.There is repetition.– There is a strong stimulus asscoiated with There is a strong stimulus asscoiated with

the information eg colour, smell.the information eg colour, smell. Scientists have produced models for Scientists have produced models for

the human memory but these are the human memory but these are inadequate.inadequate.