Brain and Mind Revision

1. Brain and Mind Revision

2. 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.

3. 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.

4. Central Nervous System • Coordination of responses is through neurones linking receptors and effectors via a central nervous system.

5. Neurones • 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.

6. Synapses • 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.

7. Synapses

8. 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.

9. 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.

10. Reflex Arcs Sensory Neurone Receptor Synapse MotorNeurone Effector

11. 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.

12. 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.

13. Learning • 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.

14. 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)

15. Memory • 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.