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Effects of Illumination on Suprachiasmatic Nucleus Electrical Discharge a
Author(s) -
GROOS GERARD A.,
MEIJER JOHANNA H.
Publication year - 1985
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1985.tb11806.x
Subject(s) - annals , library science , humanities , history , art , classics , computer science
Among the many biological rhythms found in higher vertebrates, those with an annual or a daily period are most prominent. The daily rhythms closely parallel the rotation of the earth around its axis, whereas yearly rhythms follow the revolution around the sun. Both classes of rhythms have developed as an adaptation to the considerable environmental changes that result from the earth's revolution (annual rhythms) and its rotation (circadian rhythms). Vertebrate circadian rhythms are controlled by pacemaker structures in the neuroendocrine system. These pacemakers produce intrinsic circadian oscillations. To adapt to the 24-hour period of the earth's rotation, the pacemakers synchronize to the daily light-dark cycle.' Through this process of photic entrainment, the pacemakers maintain a steady phase relation with the solar day. By contrast, many annual rhythms are not self-sustaining. They depend on photoperiodic time measurement, that is, the animal responds to the passing seasons by monitoring the annual changes in the length of the day. In order to time the photoperiod, animals may use a circadian pacemaker. In this case the circadian pacemaker is an integral component of the photoperiodic time measurement system.Is2 It is a basic tenet that this system is not only capable of monitoring the environmental light-dark cycle for pacemaker entrainment, but also that it receives information about the photoperiod. In this paper we will discuss the major advances in the study of the neural mechanisms of illumination processing by the suprachiasmatic nuclei, a major circadian pacemaker in mammals and a critical component of the mechanism for photoperiodic time measurement.*