Neurotransmitter
Published: Jul 17, 2023
/
Updated: Jul 29, 2023
Written by Oseh Mathias
Founder, SpeechFit
Neurotransmitters serve as the brain's chemical messengers. They represent endogenous chemicals facilitating neurotransmission, a critical communication form within the brain. These chemicals transmit signals over a synapse from one neuron (nerve cell) to another 'target' neuron, a muscle cell, or a gland cell[1].
The process of neurotransmission initiates in the neuron's cell body, where these substances are synthesised from various precursors, typically amino acids. Once synthesised, neurotransmitters are stored in vesicles at the terminal of the axon. When an action potential (an electrical energy surge) arrives at the axon terminal, it instigates these vesicles to merge with the cell membrane, releasing their neurotransmitter content into the synaptic cleft. The neurotransmitters subsequently bind to specific receptors on the target cell, resulting in either an excitatory or inhibitory impact on the target cell, contingent on the receptor and neurotransmitter type. After the neurotransmitters are released, their impact is terminated by reuptake (the neurotransmitter being reabsorbed into the neuron), enzyme degradation, or diffusion[2].
Here's a simplified table of some common neurotransmitters and their general function:
| Neurotransmitter | Excitatory/Inhibitory | Primary Function |
|---|---|---|
| Glutamate | Mostly Excitatory | Plays a key role in synaptic plasticity, which is involved in learning and memory |
| GABA (gamma-aminobutyric acid) | Mostly Inhibitory | Contributes to motor control, vision, and many other cortical functions; also regulates anxiety |
| Dopamine | Both (depending on the type of receptors) | Involved in reward and pleasure systems, motor function, and hormone regulation |
| Serotonin | Mostly Inhibitory | Modulates mood, social behavior, appetite, digestion, sleep, and memory |
| Norepinephrine | Mostly Excitatory | Involved in attentiveness, emotions, sleeping, dreaming, and learning |
| Acetylcholine | Both (depending on the type of receptors) | Involved in learning, memory, and mood regulation; also plays a role in stimulating muscle contraction |
| Histamine | Mostly Excitatory | Involved in the inflammatory response and has a central role as a neuromodulator |
| Glycine | Mostly Inhibitory | Plays a crucial role in the functioning of the central nervous system (CNS), specifically in spinal cord reflexes and motor behavior. It is also involved in the regulation of sleep. |
| Taurine | Mostly Inhibitory | Involved in various physiological functions such as bile salt formation, ion movement regulation, hearing, and immune system modulation |
| Adrenaline (Epinephrine) | Mostly Excitatory | Involved in the fight-or-flight response, arousal, and regulation of sleep-wake cycle and emotions |
Whether a neurotransmitter is inhibitory or excitatory can depend on what type of receptor it binds to. For instance, dopamine can have both excitatory and inhibitory effects depending on the receptor, and while GABA is generally inhibitory, under certain circumstances it can be excitatory. Additionally, this table simplifies complex functions that often involve multiple neurotransmitters working together, and the role of a neurotransmitter can vary depending on the specific neural circuit it is part of[4].
A balance of neurotransmitters is crucial for maintaining mental health. Disregulation of neurotransmitters can lead to various diseases. For instance, a deficiency in dopamine can lead to Parkinson's disease, characterised by motor impairments. Similarly, an excess of the neurotransmitter glutamate, or oversensitivity to it, can lead to excitotoxicity, potentially causing diseases like Alzheimer's[5].
Oseh is a software engineer, entrepreneur and founder of SpeechFit. Oseh is passionate about improving health and wellbeing outcomes for neurodiverse people and healthcare providers alike.
References
Purves, D., Augustine, G. J., Fitzpatrick, D., Hall, W. C., LaMantia, A. S., McNamara, J. O., & White, L. E. (2012). Neuroscience (5th ed.). Sinauer Associates.
Bear, M. F., Connors, B. W., & Paradiso, M. A. (2020). Neuroscience: Exploring the Brain (4th ed.). Wolters Kluwer.
Evans, O. G. (2023, July 18). Neurotransmitters: Types, Function And Examples. Simply Psychology. https://www.simplypsychology.org/neurotransmitter.html
Cox, C. L. (2018). Dopamine receptor signaling. Journal of Receptors and Signal Transduction, 38(1), 89-95.
Hinz, M., Stein, A., & Uncini, T. (2012). Amino acid management of Parkinson's disease: a case study. International Journal of General Medicine, 3, 129-135.