A nerve signal (action potential) travels through a neuron beginning at the dendrites, down the axon, and to the axon terminals. The membrane of the axon is polarized, meaning the external face is is positive and the internal is negative. Once the signal arrives, the membrane depolarizes, which is the opposite of polarization.
axon
myelin
axon terminals
But how does the signal cross the synapse to get to the next neuron?
Synapse (space between two neurons)
The neurotransmitter molecules are then released from the axon terminals and into the synaptic cleft
Ca2+
The calcium channels open when the signal reaches the axon terminals, allowing the vesicles with the neurotransmitters to fuse with the axonal membrane
vesicles
neurotransmitter molecules
The molecules diffuse across the synapse (small gap between neurons) and then bind to the receptors of the next neuron's membrane
QUICK! Read here! The neurotransmitters must move very quickly! Or else, they will be removed from the synapse via diffusion.
transmitter
The ion channel closes, then releases the neurotransmitter which is now broken down
Na+
The ion channels of the receiving neuron open up, where sodium enters and the transmitters diffuse into the channel
Ion channel
- - - - - - - - - - - - -
K+
+ + + + + + + + + + +
+ + + + + + + + + + +
I hope you enjoyed learning about the communication between neurons!
Finally, repolarization occurs, where the internal face of the membrane becomes negative again and the external becomes positive. During this step, potassium ions diffuse out.
