Neurotransmitters are endogenous chemicals released by the neurons at their terminals that are used to convey, magnify and modulate nerve impulses across regions called synapses that separate two neighboring neurons. Neurons are not joined together but are separated by a microscopic space called synapse. (Brodal 2004).

Transmissions of nerve impulses depend entirely on the ability of the nerve impulse or signal to pass through the synapse. Neurotransmitters are synthesized by the cell body of the neuron before being transported to the terminal end of the neuron where they are stored in a part called the visicle. When a nerve impulse (signal) travelling in a neuron reaches the terminal end, the potential signal triggers the membrane of the neuron at the terminal to fuse with the visicle membrane resulting to release of the neurotransmitters into the synaptic cleft through diffusion. The neurotransmitter released into the synaptic cleft encounters the receptor end of the adjacent neuron which upon recognizing the neurotransmitter becomes activated. This can result to either depolarization which triggers the release of the neurotransmitter at the terminal of the neuron or hyperpolarization where the activation of the receptor does not result to release of the neurotransmitter. This two mechanism controls the flow of message between neurons. (Brodal 2004).

Once they have completed their function, neurotransmitters are removed from the synaptic cleft to prepare the synapse for the next potential action. This can be done by reuptake mechanism in which the neurotransmitter is absorbed back by active transports into the synaptic knob of the presynaptic neuron but for the case of acetylcholine it is removed by enzymatic breakdown into inactive components with the   help of acetycholinesterase. (Webster 2004).

Neurotransmitters such as dopamine play a critical role in the proper functioning of the brain. When the level of dopamine falls above or below the required levels or when abnormal dopamine is synthesized disorders such as schizophrenia and Parkinson’s disease can result.  Schizophrenia is a mental disorder caused by higher than normal levels of dopamine and is indicated by abnormalities in the perception and expression of reality. This disorder is characterized by illusions, lack of organization in memory and speech and severe memory loss. Use of psychotherapy and medication has been found to lower the chances of those diagnosed from developing full-blow schizophrenia. Some of the famous people who have been affiliated with the kind of disorder include the wife of Abraham Lincoln, Mary Todd Lincoln and John Nash, a renowned American mathematician in differential geometry. (Monali 2008).

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