Biological rhythms: Circadian rhythms

• Biological rhythms are a series of internal functions regulated by our internal clocks.
• Circadian rhythms are a type of biological rhythm, that last 24 hours, which regular body processes such as the sleep/wake cycle and change in core body temperature.
• Our biological rhythms are governed by the body's internal biological clocks called 'endogenous pacemakers' and external changes in the environment called 'exogenous zeitgebers'.
• The sleep/wake cycle

  The fact that we feel drowsy when its night-time and alert during the day demonstrates the effect of daylight (an exogenous zeitgeber) however, our sleep/wake cycle is also governed by an internal (endogenous pacemaker) called the SCN which provides information from the eye about light. Light can reset the SCN.
• AO3


  Strength) Siffre went underground w/o clocks or any light. The absence of exogenous zeitgeber altered his 24 hour sleep cycle (circadian rhythm) causing him to believe the data was earlier than it was.

  Strength) Aschoff & webber's participants resided in a bunker w/ artificial light that could be turned on/off as they pleased. They found that the participants, like siffre, had longer sleep wake cycles.

  -> Emphasises the importance of light in regulating our circadian rhythms.