The Sleep-Wake Cycle

• What are the biological cycles in the human body described in the study material?

  They occur predictably, some many times a day, some every 24 hours, and some take weeks or years.
• What is an endogenous pacemaker?

  An endogenous pacemaker is an internal body clock that helps keep track of time.
• What does the term exogenous zeitgeber refer to?

  An exogenous zeitgeber is an external environmental cue that helps regulate the internal body clock.
• What is the Latin origin of the term circadian rhythm?

  Circadian rhythm comes from the Latin words "circa" meaning around and "diem" meaning day.
• What is the primary circadian rhythm discussed in the study material?

  The sleep/wake cycle is the primary circadian rhythm discussed.
• How does light affect the sleep/wake cycle according to the study material?

  Light suppresses the production of melatonin, making you feel less sleepy.
• What happens to the endogenous pacemaker during jet lag?

  It conflicts with exogenous zeitgebers, causing a misalignment in sleep patterns.
• What is the role of the suprachiasmatic nucleus (SCN)?

  The SCN is the master clock that regulates the sleep/wake cycle.
• How does the SCN interact with the pineal gland?

  The SCN regulates the pineal gland's production of melatonin based on light exposure.
• What evidence supports the existence of a free-running circadian rhythm?

  Studies where participants were isolated from natural light showed a circadian rhythm extending beyond 24 hours.
• What did Ralph's study on hamsters demonstrate about the SCN?

  It showed that the SCN is the endogenous pacemaker responsible for the sleep/wake cycle.
• How can understanding circadian rhythms benefit health services?

  It can help in timing drug treatments and improving health outcomes.
• What implications does exposure to blue light have on sleep patterns?

  Exposure to blue light can disrupt the biological clock and affect sleep quality.
• What is chronobiology?

  Chronobiology is the study of biological rhythms and their effects on living organisms.
• How do some species adapt their circadian rhythms in extreme environments?

  Some species can turn off their circadian rhythms when conditions are not favorable, like during continuous daylight.
• What is the significance of the study on a blind man regarding circadian rhythms?

  It showed that even with social cues, the blind man had a circadian rhythm that was out of sync with society.
• Why is it suggested that humans are specialized for daytime activity?

  Humans are not specialized for nighttime activity, making it illogical to be active in the dark.
• What is a unique characteristic of nocturnal animals regarding their circadian pacemaker?

  Nocturnal animals have a circadian pacemaker that is shifted to accommodate their nighttime activity.
• What happens to the circadian rhythm of arctic reindeer during the Arctic summer?

  Arctic reindeer lose their circadian rhythm when the sun never sets during the summer.