- Neurotransmitters are chemical messengers that play a central role in the nervous system, enabling communication between neurons (nerve cells) and between neurons and other types of cells, such as muscle cells or glandular cells.
- They are essential for nearly every function in the human body, from muscle contraction and heartbeat regulation to thought processes, emotions, and memory formation. Without neurotransmitters, the complex signaling network that underlies brain and body function would not be possible.
- Neurotransmitters are released from the axon terminals of a neuron in response to an electrical impulse called an action potential. When the electrical signal reaches the end of the neuron, it triggers the opening of calcium channels, causing vesicles filled with neurotransmitter molecules to fuse with the presynaptic membrane and release their contents into the synaptic cleft—the tiny gap between neurons. The neurotransmitters then bind to specific receptors on the postsynaptic cell, altering its electrical state and influencing whether it will generate an action potential of its own. After their action, neurotransmitters are either reabsorbed (reuptake) into the presynaptic neuron, broken down by enzymes, or diffused away from the synapse.
- There are several classes of neurotransmitters, each with distinct functions. The most well-known excitatory neurotransmitter in the brain is glutamate, which increases the likelihood of an action potential and plays a vital role in learning and memory. On the other hand, gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter, reducing neural activity and helping maintain balance in the nervous system. Acetylcholine (ACh) is another key neurotransmitter involved in muscle activation, autonomic nervous system functions, and attention. Dopamine, serotonin, norepinephrine, and epinephrine are classified as monoamines, and they regulate mood, emotion, arousal, and cognition. For instance, dopamine is associated with reward, motivation, and movement, while serotonin influences mood, appetite, and sleep. Norepinephrine and epinephrine (also known as noradrenaline and adrenaline) are involved in the fight-or-flight response and arousal.
- Some neurotransmitters also act as neuromodulators, meaning they do not trigger an immediate excitatory or inhibitory effect but instead modulate the strength, duration, or sensitivity of synaptic transmission over longer periods. This modulation allows for greater complexity and flexibility in neural signaling. In addition to classical small-molecule neurotransmitters, there are also neuropeptides such as endorphins, substance P, and oxytocin, which are involved in pain perception, stress, and social bonding.
- Neurotransmitters are closely linked to mental health and neurological function. Imbalances or dysregulation of neurotransmitters are implicated in numerous disorders, including depression, anxiety, schizophrenia, bipolar disorder, Parkinson’s disease, Alzheimer’s disease, and epilepsy. For example, low serotonin levels are associated with depression, while reduced dopamine activity in certain brain regions is linked to the motor symptoms of Parkinson’s disease. As a result, many pharmacological treatments target neurotransmitter systems—SSRIs increase serotonin availability, antipsychotics block dopamine receptors, and benzodiazepines enhance GABA activity.
