Pineal Gland: anatomical review and relantioships between pace-makers and photoperiods in the synchronization of the circadians rhythms

Abstract

In the present work, we review the anatomy of the pineal gland and the light influence, to establish the synchronism of the living organisms with the nature cycles and the relationships with the cerebral pace-makers, linking photoperiods and circadian rhythms. The circadian rhythm comprises cyclic functions important for the animal temporal orientation regarding the behavioral strategies to be adopted along of the year. The principal rhythm used for the synchronization with the environment is the light-dark rhythm or photoperiod. One of major components of this rhythm is the pineal gland, which is responsible for the transduction of the photic stimulus into the hormonal secretion of melatonin. Melatonin stimulates target organs such as the suprachiasmatic nucleus and the pituitary gland to send behavior-synchronizing-neural and hormonal signals, which synchronize the photoperiod-dependent-reproductive behavior. Anatomy, embryology, microscopy, vascularization and neural paths are studied, and we concluded that pineal is the most important pace-maker of the light-dark rhythm and the light has a strong influence in the adaptative changes mediated by the pineal.