STRUCTURES AND MOLECULES INVOLVED IN GENERATION AND REGULATION OF BIOLOGICAL RHYTHMS IN VERTEBRATES AND INVERTEBRATES

Melatonin from the retina and the pineal gland functions in neuroendoc rine hierarchies. Photoreceptors - eyes and extraretinal - detect ligh t. Oscillators - pineal and suprachiasmatic nuclei - act as pacemakers . Driven neuroendocrine rhythms carry temporal hormone signals through out the body. Light controls melatonin: light sets the phase of the me latonin rhythm and determines the duration of melatonin synthesis. By these means, circadian rhythms (e.g. in locomotor activity and body te mperature) and seasonal rhythms (e.g. in reproduction) are controlled.