Biological Rhythms- Circadian Rhythm

Biological Rhythms: Distinct patterns of changes in our bodies that conforms to time changes. They are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers).

Circadian Rhythms: A type of biological rhythm, subject to a 24 hour cycle. This regulates a number of body processes such as the sleep/wake cycle and changes in core body temperature.

A01:

The sleep-wake cycle:

The circadian rhythm not only says when we should go to sleep, but when we should be awake as well. Light and darkness acts as the external signals that determine when we feel the need to go to sleep and when to wake up. The circadian rhythm also dips and rises at different times of the day, so our strongest sleep drive usually occurs in two ‘dips’ between 2-4 am and between 1-3pm. The sleepiness we experience during these circadian dips is less intense if we had sufficient sleep, and more intense when we were sleep deprived.

Siffre’s cave study:

Siffre lived underground for 61 days to study his own circadian rhythm. He had no external cues to guide his rhythms. He resurfaced on the 17^th of September, believing the date was really 20 August. On the second occasion, he spent six months in a cave in Texas. His natural circadian rhythm settled down to just over 24 hours. In each case, his ‘free-running’ biological rhythm settled down to one that was just beyond the usual 24 hours (around 25 hours). This meant that his internal body clock governed his biological rhythms.

Other research:

Aschoff and Wever (1976) convinced a group of participants…