Understanding:
• 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
