Neurotransmitters: Creation & Function
- Sylvia Rose
- 12 hours ago
- 5 min read
Neurotransmitters are the chemical messengers of communication within the human body. They transmit signals between nerve cells, influencing bodily functions, mood, behavior and muscle movement.
The brain turns thoughts into actions, memories into emotions, and perceptions into reality. Neurotransmitters orchestrate everything from a muscle twitch to complex cognitive processes.
Neurotransmitters: Construction of Thought
Neurotransmitters transmit signals across a synapse, the tiny gap between nerve cells (neurons). Each neurotransmitter conveys a unique meaning.
There are over 60 known neurotransmitters, each with a specific function.
Examples of Neurotransmitters
Dopamine: Associated with pleasure and reward, dopamine functions in motivation, movement and emotional responses. Low levels are linked to Parkinson's disease, while imbalances can contribute to addiction.
Dopamine is the primary neurotransmitter associated with the pleasure of eating. When a human eats something enjoyable, the brain releases dopamine, causing pleasure.
This feeling encourages people to seek out and consume more of that food. Overeating is associated with lack of dopamine, or reduced pleasure in food. The brain can develop a tolerance to the effects of dopamine.
This often happens with excess dopamine stimulation like drug use and addiction. The brain reduces number or sensitivity of dopamine receptors. More of the substance or behavior is needed to get the pleasure effect.
Serotonin: Known as the "feel-good" neurotransmitter, serotonin regulates mood, sleep, appetite, and social behavior. Antidepressants called SSRIs (Selective Serotonin Reuptake Inhibitors), work by increasing serotonin levels in the brain.
However, 90% of serotonin is in the digestive tract, in the cells of the gastrointestinal lining. It's created from such substances as amino acids from a person's diet. Digestive health is strongly linked to mental health.
GABA (Gamma-aminobutyric acid): The primary inhibitory neurotransmitter in the brain, GABA helps calm the nervous system, reducing anxiety and promoting relaxation. Drugs like benzodiazepines enhance GABA's effects.
Glutamate: The main excitatory neurotransmitter, glutamate is used in learning, memory, and cognitive function. Excessive glutamate can be toxic to neurons and contribute to neurological disorders.
Acetylcholine: Essential for muscle control, memory, and attention, it drives communication between nerves and muscles. Alzheimer's disease is characterized by a significant loss of acetylcholine-producing neurons.
How Neurotransmitters are Created
1. Synthesis: Neurotransmitters are synthesized from readily available precursors, often amino acids, within the neuron. The specific enzymes required for each neurotransmitter determine which precursor will be used.
Dopamine for instance is synthesized from the amino acid tyrosine, found in food like chicken, fish, dairy products and nuts. The synthesis process begins with conversion of tyrosine into L-DOPA, a precursor. This is transformed into dopamine through the work of enzymes.
2. Storage: Once synthesized, neurotransmitters are stored in small, membrane-bound sacs or vesicles, located at the end of the neuron's axon. The axon is the transmitting end, which passes the signal to other cells.
3. Release: When an electrical signal (action potential) reaches the end of the neuron, it triggers the vesicles to fuse with the cell membrane and release their neurotransmitter contents into the synapse, the gap between cells.
How Neurotransmitters Function
Once released into the synapse, neurotransmitters travel across the gap and bind to specific receptors on the receiving neuron, known as the postsynaptic neuron. Receptors accept only specific neurotransmitters.
This ensures the signal is delivered to the right destination. Binding of a neurotransmitter to its receptor triggers a change in the electrical activity of the postsynaptic neuron.
It can either excite the neuron, making it more likely to fire its own action potential, or inhibit it, making it less likely to fire.
Excitatory neurotransmitters: An example is glutamate, which increases the likelihood the receiving neuron will fire an action potential. About 90% of synapses in the brain use glutamate. It's a prevalent neurotransmitter needed for learning and memory.
Inhibitory neurotransmitters: Gamma-aminobutyric acid (GABA) is a prime example. It works to reduce neuronal activity, helping maintain balance in the brain's signaling system. GABA deficiency can cause seizures and increased anxiety.
Signal Termination
The communication cannot go on forever. Once the neurotransmitter delivers its message, it must be removed from the synapse to prevent constant stimulation. This can happen in several ways.
Reuptake: The neurotransmitter is taken back up into the presynaptic neuron to be recycled or broken down. Most serotonin is recycled this way.
Enzymatic Degradation: Enzymes in the synapse break down the neurotransmitter into inactive molecules. This is particularly true for acetylcholine, broken down by the enzyme acetylcholinesterase.
Diffusion: The neurotransmitter diffuses away from the synapse and is eventually cleared by other cells.
Facts About Neurotransmitters
Botulinum toxin (Botox): This potent neurotoxin works by blocking the release of acetylcholine, preventing muscle contractions. It's used in medicine to treat muscle spasms and cosmetically to reduce wrinkles.
Caffeine: This popular stimulant works by blocking adenosine receptors in the brain. The neurotransmitter adenosine promotes relaxation and sleepiness.
The "Gut-Brain" Connection: The digestive system contains a vast network of neurons and produces many of the same neurotransmitters as the brain, including serotonin and dopamine.
This region also modulates emotion and behavior. Serotonin, in cells lining the gastrointestinal tract, is released into blood circulation and absorbed by platelets.
Diversity: There are over 100 known neurotransmitters, each with unique functions and roles in the body. They influence various systems, from the immune response to gut functionality.
Impact on Behavior: Imbalances in neurotransmitter levels can lead to various mental health conditions, like depression.
Neuroplasticity: The brain's capacity to adapt allows neurotransmitter systems to change in response to learning and experience. Over time, skills improve as connections between neurons strengthen.
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