Though neurons pass impulses to each other between axons and dendrites, the junction where they meet creates a gap called a synaptic cleft. Neurotransmitters have the important job of carrying the nerve impulse over this gap. Essentially, neurotransmitters are messengers. They reside within tiny sacs at the tips of axons, waiting for an impulse to arrive so they can get to work.
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There are different types of neurotransmitters, and each one connects to a specific receptor within a cell membrane. They are like keys that fit into specific locks, opening a pathway into the cell so a message can be sent and received. First, a nerve impulse travels down the axon to the end, opening calcium channels so positively charged calcium ions can flow in. Neurotransmitters then move into the synaptic cleft, cross the gap, and bind to matching receptors in the opposing neuron (where a message needs to be sent). This connection opens more channels so sodium, magnesium, calcium, and other ions can flow in.
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This flow of ions changes the polarity of the cell membrane, making the cell’s charge less negative. Once the polarity changes enough, the impulse (message) is transmitted into the receiving cell. From there, this process continues and the message can flow from neuron to neuron, down an extensive network of neurons that are all linked together.

Once the neurotransmitters have done their job, reuptake receptors capture them and carry them back into their originating cell, so they can be ‘repackaged’ and wait for their next message to arrive. Once they are reabsorbed, the synapse turns off. This entire process takes about seven milliseconds, so it happens almost instantly inside your brain every moment of the day.

Understanding this process of how neurons relay impulses to each other is key to understanding mental health wellness and why ketamine therapy is so effective. Before we dive into how ketamine works in the brain, let’s go over one more important aspect of neurotransmitters.