Synaptic Transfer

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•  Synapses are junctions between neurons and between neurons and receptor or effector cells

Nerves transmit electrical impulses by changing the ionic distribution across the neuronal membrane (membrane potential)

  • Therefore, electrical signals are not able to be conducted when a semi-permeable membrane is absent

Synapses are the physical gaps that separate neurons from other cells (other neurons and receptor or effector cells)

  • Neurons transmit information across synapses by converting the electrical signal into a chemical signal

Chemical Transfer Across Synapses

  • When an action potential reaches the axon terminal, it triggers the opening of voltage-gated calcium channels
  • Calcium ions (Ca2+) diffuse into the cell and promote the fusion of vesicles (containing neurotransmitter) with the cell membrane
  • The neurotransmitters are released from the axon terminal by exocytosis and cross the synaptic cleft
  • Neurotransmitters bind to specific receptors on the post-synaptic membrane and open ligand-gated ion channels
  • The opening of ion channels generates an electrical impulse in the post-synaptic neuron, propagating the pre-synaptic signal
  • The neurotransmitters released into the synapse are either recycled (by reuptake pumps) or degraded (by enzymatic activity)

Process of Synaptic Signal Transmission

synaptic transfer