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Brain and Mind Revision. Stimuli and Responses. In order to survive organisms need to monitor and respond to changes in the environment. A stimulus is any change in the environment. Animals move towards food and away from toxins.

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stimuli and responses
Stimuli and Responses
  • In order to survive organisms need to monitor and respond to changes in the environment.
  • A stimulus is any change in the environment.
  • Animals move towards food and away from toxins.
  • Plants grow towards light and water and are affected by gravity.
receptors and effectors
Receptors and Effectors
  • Receptors receive stimuli.
  • Effectors bring about a reaction.
  • Receptors can form part of complex organs such as the retina of the eye.
  • Effectors can also form complex organs such as a hormone secreting gland or a muscle.
central nervous system
Central Nervous System
  • Coordination of responses is through neurones linking receptors and effectors via a central nervous system.
  • Neurones are cells where the cytoplasm forms fibres covered in a membrane called an axon.
  • Some axons are covered in fatty sheaths which insulate and speed up impulses.
  • Receptor cells send impulses along sensory neurones to the CNS.
  • There are gaps between neurones called synapses.
  • When impulses reach the end of sensory neurones chemicals are produced that diffuse across the synapse and bind to receptors on the motor neurone.
  • This causes the motor neurone to produce a new impulse.
drugs and synapses
Drugs and Synapses
  • Some drugs affect the transmission of impulses across synapses.
  • Drugs such as Ecstasy and Prozac prevent the re-uptake of serotonin by blocking re-uptake channels in the sensory neurone leading to a feeling of well being.
  • Toxins such as curare block the receptors on the motor neurone and prevent transmissions of the impulse across the synapse causing paralysis.
simple reflexes
Simple Reflexes
  • Reflex arcs produce rapid involuntary responses called reflexes.
  • Simple animals rely on reflexes for the majority of responses.
  • These reflexes enable the animal to respond to food, predators, mates etc.
  • The disadvantage of such responses is that they stop the animal responding to new situations.
reflex arcs
Reflex Arcs

Sensory Neurone





conditioned reflex
Conditioned Reflex
  • A new response can be learned by associating a secondary stimulus with a primary stimulus.
  • Pavlov got dogs to associate a bell ringing with food.
  • The dogs then salivated when the bell rang.
  • The secondary response is nothing to do with the primary response.
conditioned reflexes
Conditioned Reflexes
  • Conditioned reflexes provide advantages

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

  • The brain can adapt reflexes in certain situations eg holding on to a hot plate.
  • This provides the ability to adapt to new situations.
  • Mammals have large brains with billions of neurones.
  • Learning is the formation of neurone pathways.
  • The large number of potential pathways provides the ability to adapt.
  • Strengthening pathways by repetitions helps develop learning.
  • Certain pathways only develop at certain ages, eg learning speech in young children.
the brain
The Brain
  • The cerebral cortex is the part of the brain associated with memory, intelligence, language and conciousness.
  • Three main methods have been used to map the areas of the brain.
    • Patients with brain damage
    • Electrical stimulation of parts of the brain
    • Magnetic Resonance Imaging (MRI)
  • Memory can be divided into short-term and long-term.
  • Humans remember information if
    • There is a pattern.
    • There is repetition.
    • There is a strong stimulus asscoiated with the information eg colour, smell.
  • Scientists have produced models for the human memory but these are inadequate.