Circadian Rhythms Flashcards
What are Circadian Rhythms?
Biological rhythms with a cycle length of 24 hours
What are 2 examples of Circadian Rhythms?
- The Sleep-Wake Cycle
- Body Core Temperature
What is the Sleep-Wake Cycle?
The 24 hour circadian cycle that regulates when we go to sleep and when we wake up
What is the Endogenous Pacemaker in terms of the Sleep-Wake Cycle?
The SCN, which is biological chip located in the hypothalamus
What is the main Exogenous Zeitgeber in terms of the Sleep-Wake Cycle?
Light
Describe a case study into the affect that deprivation of natural light has on the Sleep-Wake Cycle
- Siffre, who spent several extended periods underground
- He spent 6 months in a Texan cave and 2 months in a Southern Alps cave
- He found that his sleep-wake cycle settled around 25 hours, and he continued to fall asleep and wake up on a regular schedule
Describe Folkard’s Clock Study
- He gradually sped up the clock being used by 12 participants living in a cave for 3 weeks without their knowledge until the supposed 24 hour day only lasted 22 hours
- They were still instructed to sleep and wake at the same time each day
- Only one participant was able to comfortably adjust to the regime
What study found similar findings to Siffre?
Ashoff & Wever’s month long bunker study, in which participants settled into a sleep-wake cycle of around 25 hours
What study suggests the influence of exogenous zeitgebers in terms of the Sleep-Wake Cycle?
- Campbell & Murphy, in which 16 participants were woken at various times and had a light pad shone on the back of their knee
- This production a deviation to their usual sleep-wake cycle, in some cases of up to 3 hours
What study suggests an evolutionary basis in terms of the Sleep-Wake Cycle?
- DeCoursey’s chipmunk study, in which he destroyed the SCN in the brains of 30 chipmunks
- They were then returned to their natural habitat
- Most of the chipmunks died due to their sleep-wake cycle dissipating, leaving them vulnerable to attack from predators, suggesting the sleep-wake cycle developed as a survival advantage
What has been suggested in terms of typical teenage chronotype?
- Wolfson & Carskadon suggested that ideally the school day start a few hour later in order to accommodate for it
- Further research suggests that this will improve academic and behavioural performance and eliminate social jet lag
What is the typical teenage chronotype?
The typical teenage sleep pattern as a result of hormonal changes, meaning teenagers are inclined to not feel tired until later and find it more difficult to wake up early
What real world evidence is there to support the influence of the Sleep-Wake Cycle?
Shift work, which is associated with poor cognitive functioning and major accidents (eg. Chernobyl) as a result of it disrupting the sleep-wake cycle
What is Body Core Temperature?
The 24 hour circadian cycle that regulates body temperature, peaking at 6pm and dipping at 4am
What link has been made between Body Core Temperature and Cognitive Performance?
Cognitive performance tends to better when core body temperature is higher
