Biological rhythms - patterns of change in the body that conform to cyclical time periods, they are influenced by biological body clocks and external changes to the environment
Circadian rhythms - rhythms that last around 24 hours e.g. sleep/wake cycle and body temp
The suprachiasmatic nucleus (SCN)
Our circadian rhythms are driven by our body clocks, found in all cells, synchronised by master circadian pacemaker - suprachiasmatic nuclei, found in hypothalamus
Must be constantly reset so our bodies are in synch with outside world
Light is primary input, setting body clock to correct time Is 'photoentrainment'
Sleep/wake cycle
SCN lies above optic chiasm - provides info from light-sensitive cells to coordinate the activity of the entire circadian system
Most familiar is sleep/wake system - drowsy at night and alert in day, demonstrates the effect of daylight on the sleep/wake cycle
Siffre's research
Spent extended periods in a cave to study the effects on his biological rhythms, deprived of exposure to natural light and sound
Resurfaced mid-September - believed it to be August
6-month cave study - Texan cave
His free-running biological rhythm came to 25 hours - continued to fall asleep and wake up on a regular cycle
Our natural cycle is closer to 25 hours but is entrained by EZs
Ashoff and Weber's research
4 weeks in WW2 bunker
Circaidan rhythm between 24 and 25 hours
Longer than expected
Folkard's research
Cave study - 3 weeks
Go to bed at 11:45, wake at 7:45
Eventually sped up clock to 22 22-hour day - only one participant could comfortably adjust
Kept with natural body clock of their circadian sleep/wake cycle
Strong-freerunning circadian rhythms can't be overridden by EZs
