biological rhythms

• What is an infradian rhythm?

  It is a biological rhythm with a frequency of one complete cycle occurring less than once every 24 hours.
• What are the two factors that entrain infradian rhythms?

  Endogenous pacemakers and exogenous zeitgebers.
• What are notable examples of infradian rhythms?

  The menstrual cycle and seasonal affective disorder (SAD).
• What did McClintock et al (1998) demonstrate regarding menstrual cycle synchronisation?

  They found menstrual cycle synchronisation among 29 women with irregular periods.
• How did McClintock et al (1998) conduct their study on menstrual synchronisation?

  They collected pheromones from 9 women and applied them to the upper lip of 20 women on specific days of their cycle.
• What were the findings of McClintock et al (1998) regarding cycle lengths?

  Recipients had shorter cycles with follicular phase compounds and longer cycles with ovulatory compounds.
• What is seasonal affective disorder (SAD) and how is it related to biological rhythms?

  SAD is an infradian disorder caused by disruption to the sleep-wake cycle, commonly occurring in winter.
• How does melatonin secretion relate to SAD?

  Longer nights lead to increased melatonin secretion, which can cause feelings of loneliness and depression.
• What is an ultradian rhythm?

  It is a biological rhythm with a frequency of one complete cycle occurring more than once every 24 hours.
• What is a notable example of an ultradian rhythm?

  The stages of sleep, where a full sleep cycle takes 90 minutes to complete.
• What characterizes stages 1 and 2 of sleep?

  They represent the 'sleep escalator' where the participant can easily be awoken.
• What occurs during stages 3 and 4 of sleep?

  They coincide with deeper and slower delta waves compared to theta waves.
• What is REM sleep associated with?

  It is closely associated with dreaming and characterized by movement inhibition and a sensory blockade.
• What did Dement and Kleitman (1957) find regarding sleep stages?

  They found discrete periods of rapid eye movement during each of 126 nights of undisturbed sleep.
• What is a limitation of menstrual synchronisation studies according to Trevathan et al (1993)?

  They found no evidence of menstrual synchronisation in all-female participants.
• What extraneous variables did McClintock et al. not control for in their study?

  Factors such as smoking, physical activity, and alcohol consumption.
• What did Gloth et al (1999) find regarding treatments for SAD?

  Vitamin D supplements improved depression measures, while phototherapy showed no significant change.
• What implication does Gloth et al (1999) suggest about melatonin and serotonin in SAD?

  Melatonin and serotonin levels may have little role in the development of SAD.
• What did Luo et al (2003) study regarding pheromones in animals?

  They found that mammals encode social and reproductive information through pheromonal signals.
• What are endogenous pacemakers?

  Internal bodily regulators of biological rhythms that entrain these rhythms to cyclical periods.
• What role does the suprachiasmatic nucleus (SCN) play in biological rhythms?

  It processes information about daylight and triggers melatonin release from the pineal gland.
• How does the SCN affect melatonin and serotonin production during the day and night?

  It increases melatonin at night and decreases it during the day, affecting serotonin levels accordingly.
• What did DeCoursey et al (2000) demonstrate about the SCN?

  They found that chipmunks with lesioned SCNs had disrupted circadian rhythms and many died shortly after.
• What did Ralph et al find regarding SCN cells in hamsters?

  They found that the circadian rhythm was determined by the donor's SCN cells, regardless of the host's genotype.
• What are exogenous zeitgebers?

  External environmental changes that entrain biological rhythms to cyclical time periods.
• How do social cues act as exogenous zeitgebers?

  They include set meal times and bed times that help regulate sleep-wake cycles.
• What did Siffre et al (1967) demonstrate about light as an exogenous zeitgeber?

  Light can entrain biological rhythms even when not detected by the eyes.
• What did Damiola et al find regarding peripheral oscillators?

  They found that liver cells in mice could experience circadian rhythm changes independently of the SCN.
• What ethical issues arise from animal research in biological rhythms?

  Deliberately putting animals in harm's way breaches ethical guidelines of protection from harm.
• What limitation exists in generalizing animal studies to humans?

  Differences in physiology and types of circadian rhythms limit ecological validity.
• What did Miles et al (1977) report about a man with a unique sleep-wake cycle?

  He had a sleep-wake cycle of 24.9 hours that could not be altered by stimulants or sedatives.
• What does the case reported by Miles et al (1977) suggest about the influence of exogenous and endogenous factors?

  It suggests that their influence may be overestimated.