Endogenous chemicals that transmit signals across a synapse from one neuron to another.
Neurotransmitters are the body's chemical messengers. They are the molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles. Communication between neurons can either be excitatory or inhibitory. Excitatory neurotransmitters stimulate the brain, while inhibitory ones reduce stimulation. Some neurotransmitters can perform both functions, depending on the receptors present.
There are many different types of neurotransmitters, each with its own specific role and function. Some of the most well-known neurotransmitters include dopamine, serotonin, norepinephrine, and acetylcholine. Each of these neurotransmitters has a unique role in the body and brain, affecting everything from mood, sleep, heart rate, to basic bodily functions like breathing.
The process of neurotransmission begins with the synthesis of the neurotransmitter. This can occur in various ways depending on the specific neurotransmitter. Once synthesized, neurotransmitters are stored in vesicles within the neuron. When an electrical signal, known as an action potential, reaches the neuron, it triggers the release of the neurotransmitter into the synaptic cleft, the small gap between neurons. The neurotransmitter then binds to receptors on the receiving neuron, triggering a response.
The neurotransmitter's action is terminated by reuptake, enzymatic degradation, or diffusion. Reuptake is a process where the neurotransmitter is pumped back into the neuron that released it, ready to be reused. Enzymatic degradation occurs when specific enzymes break down the neurotransmitter. In diffusion, the neurotransmitter simply drifts away, out of the synaptic cleft.
Understanding neurotransmitters and their functions is crucial to understanding how the brain works. It's also key to understanding a wide range of psychological disorders and illnesses. For example, low levels of the neurotransmitter serotonin are associated with depression, while high levels of dopamine are associated with schizophrenia.
In the following units, we will delve deeper into two of the most well-known neurotransmitters: dopamine and serotonin. We will explore their roles in the brain, their effects on behavior and cognition, and how imbalances in these neurotransmitters can lead to psychological disorders.
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