Circadian Rhythms Flashcards

Flashcards covering key concepts related to biological rhythms, circadian rhythms, and related research.

What are biological rhythms influenced by?

Endogenous pacemakers (internal body clocks) and exogenous zeitgebers (external changes in the environment).

What is a circadian rhythm?

A type of biological rhythm that operates according to a 24-hour cycle, such as the sleep/wake cycle.

What is the role of daylight in the sleep/wake cycle?

Daylight is an exogenous zeitgeber that affects our sleep/wake cycle, causing us to feel drowsy at night and alert during the day.

What was Siffre’s cave study’s procedure?

Spent multiple extedned periods underground - 2 months in a cave woithout exposure to natural light and sound. A decade later he spent another 6 months in a cave.

What were Siffre’s findings?

In both cases, his free-running biological rhythm adjusted to a 25-hour cycle as he continued to fall asleep and wake up on a regular schedule. This suggests that the absence of exogenous zeitgebers can lengthen the sleep/wake cycle, as he also misjudged the date after his 2-month stay.

What was Folkard’s procedure?

12 PPs spent 3 weeks in a dark cave, going to bed at exactly 11.45pm and getting up at 7.45pm. Researchers gradually speeded up the clock and made the day last 22 hours rather than 24 – participants were unaware of this

What did Folkard et al. (1985) find when speeding up the clock in a dark cave experiment?

Only one PP comfortably adjusted to a 22-hour day, suggesting a strong free-running circadian rhythm that cannoot be influenced by exogenouss zeitgebers.

What is the typical range of variation in core body temperature over a day?

Approximately 2°C.

How does core body temperature vary throughout the day?

Decreases to 36°C around 4am and increases to 38°C aaround 6pm.

What does a higher core body temperature relate to, cognitively?

Better cognitive performance.

What did Folkard et al. (1977) discover about children's recall and the time of day?

Children who heard stories at 3pm showed better recall compared to those who heard them at 9am.

According to Gupta (1991), when did participants perform better on IQ tests?

At 7pm compared to 2pm and 9am.

How can circadian rhythms be practically applied to shift work

Can help researchers understand the effects of desynchronisation (when rhythms are disrupted). Boivin found that night shift workers experience a period of reduced concentration around 6 am (aka a circadian trough), where mistakes are more likely.

How do teenagers' circadian rhythms typically differ from those of adults?

They typically begin 2 hours later.

How does Circadian rhythms suffer from ethical implications?

Changes to social policy, regarding night shift work, may have economic implications.

What is a limitation of research into circadian rhythms regarding population validity?

Studies often consist of case studies or small sample sizes, making generalisation difficult.

How is circadian rhythms biologically deterministic?

We have no conscious control over our circadian rhythms.