Neurones have three basic functions: sending sensory information to the brain, sending motor commands from the brain, and shuttling information around the brain itself. Information is handled within the neurone as electrical charges triggered by neurotransmitters received from other (pre-synaptic) neurones. Any resulting action potential (a small region of voltage change that exists as a result of the rapid movement of ions in and out of the neurone) travels down the axon to the synaptic buttons, where it triggers the release of neurotransmitters which in turn produce changes in electrical charge on the post-synaptic neurone.
Communication between neurones occurs when a neurotransmitter is released from the synaptic button of the pre-synaptic neurone into the synaptic cleft, where it diffuses across and binds to receptors on the post-synaptic neurone. The signal, for most neurotransmitters, is terminated by reuptake of the neurotransmitter into the pre-synaptic neurone.
Neurotransmitters work in circuits or systems and these interact to produce cognition, experience and behaviour. Drugs can affect the functioning of neurones by ‘mimicking’ the structure of neurotransmitters, and can have agonist or antagonist effects at any of the various stages of synaptic transmission to produce change.