Peptides regulate three distinct biological domains: hormones, the nervous system, and growth and repair. Each domain relies on different peptide signals, and each signal uses the same basic design principle.
Hormonal signals travel through the bloodstream and affect organs far from their source. Insulin regulates blood sugar by signaling muscle and fat cells to take up glucose. Oxytocin triggers bonding and social behavior. Leptin signals fullness to the brain.
Nervous system signals are local and fast. Endorphins dull pain perception by binding to receptors in the brain and spinal cord. Neuropeptide Y suppresses appetite during times of stress. GABA promotes calm and sleep.
Growth and repair signals orchestrate cellular recovery. Growth hormone and IGF-1 build muscle. Fibroblast growth factor directs wound healing and tissue regeneration. These signals activate dormant cells and trigger protein synthesis.
One signal, one receiver. The target changes. The mechanism does not.