Different types of synapses

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  • Created by: 08rmorris
  • Created on: 04-04-15 11:25
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  • Different types of synapse
    • 1. Excitatory ion-channel synapses
      • These synapses have neuroreceptors that are sodium (Na+) channels
        • When the channels open, positive ions diffuse in, causing a local depolarisation called an excitatory postsynaptic potential (EPSP)
          • Making an action potential more likely
            • acetylcholine glutamate asparate
    • 2. Inhibatory ion-channel synapses
      • These synapses have neuroreceptors that are chloride (Cl-) channels.
        • When the channels open, negative ions diffuse in causing a local hyper polarisation called an inhibitory postsynaptic potential (IPSP)
          • making an action potential less likely
            • An impulse in one neurone can inhibit an impulse in the next
              • Glycine GABA
    • 3. Non-channel synapses
      • These have neuroreceptors that are not channels at all
        • but instead are membrane-bound enzymes
          • When activated by the NT, they catalyse the production of a "messenger chemical" inside the cell, which in turn can affect many aspects of the cell's metabolism
            • In particular they can alter the number and sensitivity  of the ion channel receptors in the same cell
              • These synapses are involved in slow and along-lasting responses like learning and memory
                • adrenaline noradrenaline dopamine serotonin endorphin angiotensin acetylcholine
    • 4. Neuromuscular junctions
      • these are synapses formed between effector neurones and muscle cells
        • they always use the NT acetylcholine and are aways excitatory
          • Effector neurones also form specialised synapses with secretory cells
    • 5. Electrical synapses
      • in these synapses the membranes of the 2 cells actually touch
        • they share proteins
          • This allows the action potential to pass directly from one membrane to the next without using a NT
            • They are very fast, but are quite rare, found only in the heart and the eye

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