Second Messenger Systems

**Definition:** Systems in which an intracellular signal is generated in response to an intercellular primary messenger such as a hormone or neurotransmitter. They are intermediate signals in cellular processes such as metabolism, secretion, contraction, phototransduction, and cell growth. Examples of second messenger systems are the adenyl cyclase-cyclic AMP system, the phosphatidylinositol diphosphate-inositol triphosphate system, and the cyclic GMP system.

**Tree numbers:** - G02.111.820.800 - G04.835.800

**Synonyms:** - Intracellular Second Messengers