B6 - Synapses & the Brain

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  • B6 - Synapses & the Brain
    • Synapses & Drug Effects
      • There are tiny gaps (synapses) between neurons in the reflex arc
      • Nerve impulses must cross these gaps to get them from one neuron to the next - special chemicals pass the impulses across synapses
      • This is how the process works:
        • 1. A nerve impulse gets to the end of a sensory neuron
        • 2. The sensory neuron releases the transmitter chemical into the synapse
        • 3. The transmitter chemical diffuses across the synapse
        • 4. The transmitter chemical arrives at the receptor molecules on the motor neurons membrane - the molecules are the correct shape to bind the receptor olecules
        • 6. The chemical is absorbed back into the sensory neuron to be used again
        • 5. A nerve impulse is stimulate in the motor neuron
      • Some drugs, including ecstasy, beta blockers, & prozac, make it difficult for impulses to get across the synapse
        • Ecstasy (MDMA) blocks the place that removes serotonin - the serotonin concentration increases
          • This makes the Ecstasy user happy for a short while but can be seriously harmful
      • Serotonin (a transmitter chemical) is released at some brain synapses - this gives a feeling of pleasure & sensory neurons later remove the serotonin
    • Inside the brain
      • Different regions of the brain do different jobs
      • Neuroscientists map the brain by:
        • Studying patients with brain damage
        • Electricity stimulating different parts of the brain
        • Doing MRI scans
      • The cerebral Cortex is the part of the brain most closely linked to intelligence, language, memory, & conciousness (MILC)
    • Reflex Responses
      • Animals can learn a reflex response to a new stimulus - the new stimulus (secondary stimulus) becomes linked to the primary stimulus - this s called conditioning
      • Pavlov taught a dog to salivate when it heard a bell ring:
        • 1. The dogs simple reflex was to salivate when it was given food
        • 2. Pavlov rang a bell whilst the dog was eating
        • 3. After a while, the dog salivated every time it heard the bell, even when there was no food
        • In this conditioned reflex, the stimulus (ringing the bell) became linked to food - the final response (salivating) had no direct connection to the stimulus
      • Conditioned reflexes are a simple form of learning - They increase an animals chance of survival

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