What happens at the synapse?
- The synapse is the region of communication between an axon (or synaptic) terminal and another cell. They can be chemical or electrical.
-Chemical Synapse- when the action potential reaches the end of an axon, it stops and the information is transmitted to the next cell. Do have a synaptic cleft, which is what prevents the action potential from moving directly to the next cell.
- Synaptic Cleft- a narrow gap in between the axon terminal of the presynaptic (sending) neuron and the postsynaptic (receiving) neuron. Exist only at a chemical synapse.
- Neurotransmitter- a chemical messenger that carries information from a transmitting neuron to a receiving cell (either another neuron or an effector cell).
- Synaptic Vesicles- contain the neurotransmitters in the sending neuron's synaptic terminals.
2. The action potential triggers chemical changes that cause the synaptic vesicles (that are carrying neurons) to fuse with the membrane of the sending neuron.
3. The vesicles release the neurotransmitter into the synaptic cleft, where the neurotransmitter molecules disperse across the synaptic cleft.
4. This step varies (depending on the type of chemical synapse), but in one common type, the already released neurotransmitter binds to receptor molecules on the plasma membrane of the receiving neuron.
5. When the neurotransmitter binds to the receptor molecule, the chemically gated ion channels open in the receiving cells membrane, allowing ions to diffuse into the receiving cell, and trigger a new action potential.
6. Finally, the neurotransmitter is broken down by an enzyme, or transmitted back to the sending cell, and the ion channel closes.