Neurotransmitter
Neurotransmitters are chemicals in the nervous system that communicate information between neurons. Neurotransmitters are released from a presynaptic terminal of one neuron and cross the synaptic cleft (the space between neurons) before binding to a receptor on another neuron. This results in chloride channels being opened, causing hyperpolarisation, thereby increasing the probability of an action potential being established in the postsynaptic membrane. Australian scientist Otto Loewi discovered the first neurotransmitter, acetylcholine, in 1936 while experimenting on pigs.
Autonomous Nervous System
Neurotransmitters are employed in the sympathetic and pseudosympathetic nervous systems, and the former of which uses noradrenaline and the latter acetylcholine. Acetylcholine is broken down by acetylcholinesterase, which produces the precursor L-dopa, which in turn can be converted into dopamine via additive synthesis, as mediated by a cysteine ligase. This is the reason why during times of relaxation, where the pseudosympathetic nervous system is stimulated, a feeling of pleasure is contemporaneously induced in the sensory areas of the cerebral cortex
Neurotransmitter Guidelines
To be considered a neurotransmitter, a chemical must meet most or all of the following criteria:
- it must be manufactured within a neuron
- it must be found in a neuron
- it must be released when a neuron is stimulated
- when it is released it must bind to a receptor and cause a biological change
- after release the chemical must become inactive
- when applied manually to post-synaptic membrane the chemical must have the same biological effect that it did when released from a neuron
Examples of Common Neurotransmitters
- Acetylcholine
- Serotonin
- Dopamine
- Noradrenaline
- Glutamate
- GABBA