The Role of Synapses

• Synapse


  The junction where two neurones meet
• Synapse


  • Consists of a presynaptic knob, synaptic cleft and postsynaptic membrane
• Cholinergic synapse


  Synapse that uses acetylcholine (ACh) as a neurotransmitter
• Transmission at a synapse

  1. Electrical impulse arrives at presynaptic neurone

  2. Neurotransmitters released from vesicles at presynaptic membrane

  3. Neurotransmitters diffuse across synaptic cleft

  4. Neurotransmitters bind to receptors on postsynaptic membrane

  5. Postsynaptic neurone generates electrical impulse

  6. Neurotransmitters destroyed or recycled
• Electrical impulses cannot 'jump' across synapses
• Neurotransmitters are released from vesicles at the presynaptic membrane when an electrical impulse arrives at the end of the axon on the presynaptic neurone
• The neurotransmitters diffuse across the synaptic cleft down a concentration gradient
• The neurotransmitters temporarily bind with receptor molecules on the postsynaptic membrane
• This stimulates the postsynaptic neurone to generate an electrical impulse that then travels down the axon of the postsynaptic neurone
• The neurotransmitters are then destroyed or recycled to prevent continued stimulation of the second neurone, which could cause repeated impulses to be sent
• There are many synoptic links with synapses and transport across membranes