Brain and Behavior - Neurotransmitters and other Brain Chemicals

7 important questions on Brain and Behavior - Neurotransmitters and other Brain Chemicals

What are neurotransmitters and why are they important?

Neurotransmitters are perhaps the main chemical messengers in the brain. They are the means by which neurons communicate with each other. It is through neurotransmitters that one neuron tells another neuron to fire.

If we think of the brain as a vast economy, neurotransmitters can be seen as the currency of that economy. The exchange of neurotransmitters stimulates neurons to act.

How do neurotransmitters act at synapses?

Neurotransmitters are stored in sac-like vesicles in the axon terminals of the neuron. When the neuron fires, its axon terminals release neurotransmitters into the synaptic cleft, the space between the pre-synaptic and post-synaptic neuron.

When the neurotransmitters bind to the receptor sites on the post-synaptic neuron, they impact the likelihood that the neuron will fire. Excitatory neurotransmitters increase the likelihood of firing while inhibitory neurotransmitters decrease it.

What is the reward system?

The reward system refers to a tract of dopamine-containing neurons that are centrally involved in the experience of desire. The object of desire is not important.

This is an all-purpose motivation machine that is active in drug craving (cocaine, methamphetamine, alcohol, and cigarettes) and in gambling, eating, and sex. It may be active as well in many other activities that elicit strong motivation and desire.

The reward system is composed of the mesolimbic dopaminergic tracts, which reach from the ventral tegmental area in the midbrain to the nucleus accumbens in the forebrain.
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What are opioids, the natural pain killers?

Opoids are a form of neuromodulator that serves to dampen our pain response. They are our homemade analgesics, our natural painkillers.

One way that opiods work is to inhibit the effect of the neurotransmitter glutamate. As glutamate is an excitatory neurotransmitter, inhibiting glutamate serves to reduce brain activity, in effect to calm down the brain.

How are opiates different from opioids?

Opiates are essentially the plant form of opioids. Opiates are extracted from the sap of the opium poppy. Synthetic versions of this chemical are also called opiates.

When ingested, opiates bind to the opioid receptors in the human brain. Thus the brain responds to opiates the same way that it responds to our own endogenous (internally created) opioids.

Several very potent painkillers, such as morphine, heroin, and opium, are made from opiates. Because of the relaxing and euphoric effects of opiates opiate-based medications are popular drugs of abuse.

How do psychiatric drugs act on our brain chemicals?

The majority of psychiatric drugs act by altering one or more neurotransmitter systems. Typically the medications do not contain the actual neurotransmitters but instead contain various chemicals that regulate the action of neurotransmitters.

For example, the SSRI antidepressants block the re-absorption of serotonin. This keeps the serotonin molecules in the synapse longer, giving them more time to bind to receptor sites and, therefore, stimulate the firing of the post-synaptic neuron.

To visualize this process, imagine someone standing at your door, continuously pressing his or her finger on your doorbell.

How do drugs of abuse act on the brain?

Drugs of abuse and legitimate medications act similarly on our brain. In fact, a number of psychiatric medications are sometimes misused as drugs of abuse. Drugs of abuse ten to cause quicker and more intense pleasurable effects than other drugs. It is this 'high' that makes these drugs attractive as recreational drugs.

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