NIOSH Training for Nurses on Shift Work and Long Work Hours
Synchronization of Homeostatic and Circadian Processes
Figure 2.6a. Homeostatic sleep pressure drive and circadian wakefulness rhythm are normally synchronized.
If you are active during the day and sleep at night, homeostatic sleep pressure drive and circadian wakefulness rhythm are synchronized as illustrated in Figure 2.6a. As shown, wakefulness and sleep pressure rise during day time with the wakefulness overriding the pressure for sleep. Sleep onset occurs when sleep pressure drive is high and wakefulness is dropping. Morning awakening occurs sometime after wakefulness begins to rise and override sleep pressure.