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Second Messenger System

Meaning

The Second Messenger System describes the complex intracellular cascade where a non-hormonal, small molecule acts as an intermediary to relay a signal initiated by an extracellular ligand, such as a peptide hormone, binding to its transmembrane receptor. This system amplifies and diversifies the initial external signal into a potent internal cellular response. It is fundamental to signal transduction in many endocrine pathways.