Circadian rhythms

• What is the significance of waking up before the alarm?

  It relates to biological rhythms
• What are biological rhythms determined by?

  Internal biological clock and external changes
• What are circadian rhythms?

  Biological rhythms lasting 24 hours
• What factors influence biological rhythms?

  • Internal biological clock (endogenous pacemakers)
  • External changes in the environment (exogenous zeitgebers)
• How does daylight affect our sleep/wake cycle?

  It makes us feel drowsy at night
• What happens to our need for sleep after being awake for a long time?

  It increases due to energy use
• What is the internal circadian clock described as?

  'Free running'
• What can cause changes in the biological clock?

  Shift work and jet lag
• What is the term for your daily activity related to biological rhythms?

  Circadian rhythm
• What did Michel Siffre study during his underground stays?

  The effects on his biological rhythms
• How long did Siffre's first underground stay last?

  61 days
• What was Siffre's belief about the date after his first stay?

  He believed it was 20th August
• How long did Siffre spend in a cave in Texas?

  6 months
• What happened to Siffre's circadian rhythm as he aged?

  It ticked more slowly
• What was Siffre's circadian rhythm during his final stay?

  Just beyond 24 hours
• What is a key indicator of the circadian rhythm?

  Core body temperature
• At what time is core body temperature lowest?

  About 4:30 AM
• At what time is core body temperature highest?

  About 6 PM
• What happens to body temperature during sleep?

  It begins to drop
• Why do many people feel sleepy in the early afternoon?

  Due to a drop in body temperature
• What is the effect of homeostasis on sleep?

  It indicates the need for sleep increases
• How does the internal circadian clock function in isolation?

  It maintains a cycle of 24-25 hours
• What is the relationship between core body temperature and sleep?

  Temperature drop promotes sleep onset
• What are biological rhythms?

  Repeated patterns of changes in the body
• How many biological rhythms will be explored in the videos?

  Three biological rhythms
• What is a circadian rhythm?

  A rhythm lasting around 24 hours
• What are the two main factors controlling biological rhythms?

  Endogenous pacemakers and exogenous zeitgebers
• What does 'endogenous' mean in the context of pacemakers?

  Inside the body
• What are endogenous pacemakers?

  Internal body clocks regulating biological rhythms
• What does 'exogenous' mean in the context of zeitgebers?

  Outside the body
• What are exogenous zeitgebers?

  External cues influencing biological clocks
• What is the SCN?

  Suprachiasmatic nucleus
• Where is the SCN located?

  In the hypothalamus
• What role does the SCN play in the sleep-wake cycle?

  It regulates the timing of sleep and wakefulness
• What hormone does the pineal gland secrete?

  Melatonin
• How does light affect the SCN?

  It influences melatonin production
• What happens to melatonin production in low light?

  It increases to help us sleep
• Why is light important for circadian rhythms?

  It adjusts our internal biological clock
• What did the research by Caral in 2000 demonstrate about the SCN?

  It regulates the circadian rhythm in chipmunks
• What was the outcome for chipmunks with damaged SCN?

  They were more vulnerable to predators