The four are 1) a reactive negative-feedback system, 2) a reactive feed-forward system, 3) a predictive or circadian system, and 4) an internal or cell membrane transport system.
Keempatnya adalah 1) sistem umpan balik negatif reaktif, 2) sistem umpan maju reaktif, 3) sistem prediktif atau sirkadian, dan 4) sistem transport internal atau membran sel.