Circadian rhythms

• What are biological rhythms?

  Distinct patterns of changes in body activity
• How do biological rhythms influence bodily systems?

  They dictate how bodily systems behave
• What are the two factors that influence biological rhythms?

  Endogenous pacemakers and exogenous zeitgebers
• What are endogenous pacemakers?

  Internal body clocks regulating biological rhythms
• What are exogenous zeitgebers?

  External changes in the environment affecting rhythms
• What is a circadian rhythm?

  A biological rhythm with a 24-hour cycle
• What role does the SCN play in the sleep-wake cycle?

  It sends signals to the pineal gland
• How does low light affect melatonin secretion?

  It increases melatonin secretion, inducing drowsiness
• How does high light affect melatonin secretion?

  It decreases melatonin secretion, reducing drowsiness
• What was the aim of Siffre's 1972 cave study?

  To find how lack of zeitgebers affects rhythms
• What was the procedure of Siffre's cave study?

  Siffre stayed in a cave for six months
• What did Siffre do when he thought it was daytime?

  He phoned the research team to switch on lights
• What were Siffre's findings regarding his sleep-wake cycle?

  His average cycle was around 25 hours
• What conclusion can be drawn from Siffre's cave study?

  Both endogenous pacemakers and zeitgebers control rhythms
• What are the real-life applications of understanding circadian rhythms?

  Shift work and medical treatment timing
• Why is it difficult to generalize findings from circadian rhythm research?

  Studies often have small participant samples
• What did Duffy et al. (2001) find about sleep/wake cycles?

  Some prefer going to bed early ('larks')
• What is a limitation of Siffre's study regarding population validity?

  It lacks generalizability due to one participant