The nervous system is the command center for our bodies. It is comprised of many neurons that communicate with eachother via chemical messengers called neurotransmitters. The body has many different neurotransmitters and they all have different functions within our nervous system. Some make the nervous system more excited and some make the nervous system more quiet. Some of the more famous neurotransmitters are seratonin, dopamine, noradrenaline and GABA.
Neurotransmitters are also an important part of pain perception. Too much of excitatory neurotransmiters such as glutamate can lead to chronic pain while release of endorphins (another set of neurotransmitters) can inhibit the pain signals and calm down the nervous system leading to releaf of pain.
Many of the medications for depression and anxiety work by modulating the neurotransmitters serotonin, dopamine and norepinephrine.
Ketamines work by indirectly inhibiting dopamine and serotonin reuptake and directly by blocking the NMDA recpetor which works through the neurotransmitter called glutamate. Thus ketamine therapy can be a powerful treatment for mental health disorders such as depression, anxiety and chronic pain.