6. BIOPSYCHOLOGY (CIRCADIAN RHYTHMS) Flashcards
What are biological rhythms?
Biological rhythms are natural cycles in living organisms that regulate bodily processes, influenced by both internal biological ‘clocks’ (endogenous pacemakers) and external environmental changes (exogenous zeitgebers).
What are the three types of biological rhythms?
- Circadian rhythms (24-hour cycle), 2. Ultradian rhythms (multiple cycles within 24 hours), 3. Infradian rhythms (less than one cycle in 24 hours).
What is a circadian rhythm?
A circadian rhythm is a biological cycle that lasts approximately 24 hours, regulating processes such as the sleep/wake cycle and core body temperature.
How is the sleep-wake cycle controlled?
The sleep-wake cycle is controlled by the suprachiasmatic nucleus (SCN) in the hypothalamus, influenced by light and darkness (external signals or exogenous zeitgebers).
What is the role of the suprachiasmatic nucleus (SCN)?
The SCN regulates the sleep/wake cycle by receiving light signals and coordinating the body’s internal clock to match the external environment.
What happens to the body temperature during the circadian rhythm?
Core body temperature is lowest around 4:30 am (about 36°C) and highest around 6 pm. Sleep begins as the body temperature drops, and alertness rises as it increases during the last hours of sleep.
What are circadian ‘dips’?
Circadian dips are times during the day, typically between 2-4 am and 1-3 pm, when the body experiences a natural increase in sleepiness due to internal rhythms.
What is the “free-running” internal circadian clock?
The free-running circadian clock maintains a cycle of 24-25 hours even in the absence of external cues, though it may become less accurate without cues like light.
What was Siffre’s (1975) study on circadian rhythms?
Siffre spent 6 months isolated in a dark cave without clocks or natural light, finding that his circadian rhythm adjusted to a 25-30 hour sleep/wake cycle, suggesting the presence of an internal body clock influenced by external factors.
What did Siffre’s study suggest about endogenous pacemakers and exogenous zeitgebers?
Siffre’s research suggests that endogenous pacemakers maintain a circadian rhythm in the absence of exogenous zeitgebers, but the rhythm is more stable when environmental cues, like light, are present.
What is a limitation of Siffre’s study?
Siffre’s study used artificial light, which could have influenced his circadian rhythm, and his results may not apply universally since he was the only participant, limiting generalizability.
How does artificial light affect circadian rhythms?
Research by Czeisler et al. (1999) showed that artificial light can significantly alter circadian rhythms, suggesting that Siffre’s use of artificial light might have impacted his sleep-wake cycle.
How do circadian rhythms apply to shift work?
Research shows that shift workers experience reduced concentration during the night, leading to accidents and health issues like heart disease, suggesting the importance of aligning work schedules with circadian rhythms to improve health and performance.
What are individual differences in circadian rhythms?
Research by Czeisler et al. (1999) and Duffy et al. (2001) found that sleep/wake cycles vary significantly between individuals, with some preferring to sleep early, while others prefer staying up late. This challenges the idea of a universal circadian rhythm.
What is an ultradian rhythm?
An ultradian rhythm is a biological cycle that lasts less than 24 hours and includes repeated cycles within the day, such as the stages of sleep or appetite cycles.
