What are Neurotransmitters

"Communication of information between neurons is accomplished by movement of chemicals across a small gap called the synapse. Chemicals, called neurotransmitters, are released from one neuron at the presynaptic nerve terminal. Neurotransmitters then cross the synapse where they may be accepted by the next neuron at a specialized site called a receptor. The action that follows activation of a receptor site may be either depolarization (an excitatory postsynaptic potential) or hyperpolarization (an inhibitory postsynaptic potential). A depolarization makes it MORE likely that an action potential will fire; a hyperpolarization makes it LESS likely that an action potential will fire.....


Neurotransmitter Criteria

Neuroscientists have set up a few guidelines or criteria to prove that a chemical is really a neurotransmitter. Not all of the neurotransmitters that you have heard about may actually meet every one of these criteria.

• The chemical must be produced within a neuron.
• The chemical must be found within a neuron.
• When a neuron is stimulated (depolarized), a neuron must release the chemical.
• When a chemical is released, it must act on a post-synaptic receptor and cause a biological effect.
• After a chemical is released, it must be inactivated. Inactivation can be through a reuptake mechanism or by an enzyme that stops the action of the chemical.

Neurotransmitters will bind only to specific receptors on the postsynaptic membrane that recognize them.."

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