title: Sleep and activity: their relation to the 24-hour clock.
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001683:Biological Clocks / Q000502:physiology*; D001766:Blindness; D002540:Cerebral Cortex / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D004326:Drinking / Q000502:physiology; D004435:Eating / Q000502:physiology; D004702:Endocrine Glands / Q000502:physiology; D008027:Light; D009424:Nervous System Physiological Phenomena; D010507:Periodicity; D051381:Rats; D012154:Reticular Formation / Q000502:physiology*; D012890:Sleep / Q000502:physiology*