Circadian Rhythms

Are biological cycles lasting around 24 hours, like the sleep wake cycle, ehich is usually facilitated by checks and regular events
There is a free running cycle controlled by an endogenous pacemaker working as a body clock
Another circadian rhythm is body temperature, rising and declining as an indicator of metabolic rate, 4a.m. being the lowest point
Siffre 1975 spent 6 months in a cave with no external cues as to time. Artifical lights would come on when he moved and was awake but gave no clue to whether it was light outside. His sleep wake cycle ranged between 25-30hrs. After 179 days had passed Siffre thought only 151 days had passed. This suggests human body clocks do keep fairly reliable sleep/wake cycle that on average very close to 24 hours
1. Could be an issue with this study in that the use of artifical light is known to influence the circadian rhythms. This means that the sleep/wale cycle is a result of a combination between endogenous pacemaker and exogenous zeitgeber
Aschoff and Weber; undergroud WWII bunker, participants had no social or enviromental cues, showed circadian rhythm of 24/25 hours some up to 29
Folkard et al. 12 participants in a cave for three weeks, agreed to 11.45pm bedtime and get up at 7.45 am, the clock started at 24 hours as normal and then speeded up to 22. All participants kept up at first but inly one was able to adapt to 22 hours. the internal rhythm cannot be entrained by and external cue of less than 24 hours
Case study; man blind form birth had acircadian rhythm of 24.9 hours despite clocks and social cues
Flawed methodology; Czeisler et al (1999) abl to adjust paricipants circaidan rhythms in the range 22-28 hours with dim light
Individual differences; 1. cycle length can vary 13-65 hours (Czeisler) 2. Cycle onset (duffy) morning people (6am to 10pm) evening people (10am to 1pm)

Next up

Circadian Rhythms

Description

Resource summary

Similar

	Created by harry_bygraves almost 11 years ago