How do neuropeptides differ from traditional neurotransmitters?

Neuropeptides differ from traditional neurotransmitters primarily because they are larger chains of amino acids. This structural difference is significant in terms of how they function within the nervous system. Neuropeptides typically consist of 3 to 40 amino acids, while traditional neurotransmitters, such as dopamine or serotonin, are often composed of a single amino acid or small groups of amino acids.

This larger size allows neuropeptides to engage in various biological processes, including modulating the activity of neurotransmitters and influencing the overall excitability of neurons. Their complexity also contributes to their role in longer-lasting effects and diverse physiological responses, such as pain modulation, stress responses, and eating behaviors, which are not solely dependent on immediate synaptic transmission.

While the other characteristics mentioned in the options can pertain to differences between neuropeptides and neurotransmitters, the foundational distinction based on size directly influences their mechanisms of action and role in neurobiology.