2.4 : ニューロンの通信

Neurons communicate by sending electrochemical signals that travel along their axons to neighboring neurons.

When the electrical charge within a neuron exceeds a certain threshold, it triggers an action potential. This electrical signal travels down the axon to the axon terminal, where it is transmitted to the next neuron through specialized structures known as synapses.

Synapses are classified into two main types — electrical and chemical.

Electrical synapses feature direct connections between neurons through gap junctions. This allows for the immediate and direct transfer of ions, facilitating impulse transmission. This type of synaptic transmission is very fast and is typically found in areas of the brain that require rapid coordination.

In contrast, chemical synapses involve the release of neurotransmitters, chemical messengers that travel across the synaptic cleft between neurons.

When an electrical impulse, or action potential, reaches the presynaptic neuron, it triggers the release of neurotransmitters from vesicles into the synaptic cleft.

These neurotransmitters then bind to receptor proteins on the postsynaptic neuron, causing changes that can either excite or inhibit the neuron, depending on the type of neurotransmitter and receptor involved.