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Nervous System 3 (Electrical synapse (Pre-synaptic membrane is close to…

- - - - this is because depolarising an hyperpolarising current can spread through junctions
- - - - Presynaptic axon terminal – dendrite = axodendritic
      - Presynaptic axon terminal – cell body = axosomatic
      - Presynaptic axon terminal – post synaptic axon terminal = axoaxonic
      - Classified by where pre-synaptic terminal contacts post-synaptic
- - - - these open when axon terminal membrane is polarised
        
        Occurs upon arrival of AP at axon terminal
  - - - Overview
        
        Derived from amino acids (NH2) group
        
        Do not contain amino acids
        
        Include histamine, serotonin, dopamine, nor/epinephrine
        
        Synthesized in cytosol of axon terminal
        
        Do not cause opening of ionic gates in the postsynaptic membrane
        
        Act through a second messenger to open gates (usually cyclic AMP)
    - - Overview
        
        Made from acetyl CoA & Choline
        
        Neurons that synthesize acetyl CoA are known as cholinergic neurons
        
        Choline not syntheised by cells (only a small amount which is not sufficient enough) but obtained from diet
        
        Degraded by acetylechloinesterase – Choline & acetate
        
        Taken back up by the presynaptic cell used again
        
        Most abundant neurotransmitter
        
        Produced in the cytoplasm of the axon terminals
        
        Has a role at specific sites in the autonomic nervous system and throughout the brain
        
        Receptors on post synaptic membrane are known as cholinergic receptors
- - - - Receives hundreds/thousands of inputs from other neurons that make synapses on it
      - Some will stimulate while others inhibit
    - - Different types of neurons in the brain have their own characteristic set of receptors and ion channels
        that enable the cell to respond in a particular way
        
        Ion channels & receptors at synapse can also undergo lasting modifications thereby preserving traces of past events
        
        In this way memories are stored
        
        Ion channels/receptors are at the heart of the machinery that enables you to act, think, feel, speak and remember
  - - - They must combine them
      - Interpret them
      - Record them
- - - - Operate by allowing electrical signals to be transmitted from neuron to target cell through gap junctions
    - - Operate through release of neurotransmitters that activate signal transduction mechanisms in target cells