Biopsychology: Neurons and Synaptic Transmission

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  • Created on: 02-05-18 20:44
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  • Neurons and Synaptic Transmission
    • Types of neuron
      • Sensory neuron - carries impulses from the PNS + receptors. They have long dendrites and short axons.
      • Relay neuron - carries impulses from sensory neurons to motor neurons. They have short dendrites and short axons.
      • Motor neuron - carries impulses from the CNS to effectors. They have short dendrites and long axons.
    • The structure of a neuron
      • The cell body contains the nucleus.
      • Dendrites extend from the cell body. They carry electrical impulses from other neurons to the cell body.
      • The axon is an extension of the neuron that carries impulses away. The axon is covered by a myelin sheath that protects it and increases the speed of impulses.
      • The myelin seath has gaps of between 0.2mm and 2mm called nodes of Ranvier. They speed up the transmission of the impulse by forcing it to 'jump' across.
        • At the end of the axon are terminal buttons that communicate with the next neuron in the chain across a gap known as the synapse.
          • When a neuron is in a resting state the inside of the cell is negatively charged compared to the outside. When a neuron is activated by a stimulus, the inside becomes positively charged for a split second.
            • This causes action potential and an electrical impulse travels down the axon towards the end of the neuron
    • Synaptic transmission
      • Neurons communicate with each other within groups called neuron networks. Neurons are separated by synapses.
      • Signals are sent electrically WITHIN the neuron, but sent chemically BETWEEN neurons across the synapse.
        • When the electrical impulse reaches the end of the neuron (the presynaptic terminal) it triggers the release of neuro-transmitter from synaptic vesicles.
      • Neuro-transmitters are chemicals that diffuse across the synapse to the post synaptic receptor site.
      • Each neuro-transmitter has its own specific molecular structure that fits into sites. They also have specialist functions.
      • Neuro-transmitters have an excitatory or inhibitory effect on other neurons.
        • Excititation = increases the likelihood that the neuron will fire and pass on the electrical impulse.
        • Inhibition = decreases the likelihood that the neuron will fire and pass on the electrical impulse.


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