The Sleep Wake Cycle: Circadian rhythm

• What are biological cycles in the body?

  Predictable cycles occurring at various intervals
• How often do some biological cycles occur?

  Some occur many times a day, others less frequently
• What is an endogenous pacemaker?

  An internal body clock that keeps time
• What does the term 'exogenous' refer to in exogenous pacemakers?

  Outside or external sources
• What is the role of exogenous pacemakers?

  They provide environmental cues to regulate time
• What is another term for the process of using external cues to regulate the internal clock?

  Entrainment
• What is a circadian rhythm?

  A biological rhythm lasting around 24 hours
• What is the most obvious circadian rhythm?

  The sleep/wake cycle
• How does light affect the sleep/wake cycle?

  Light suppresses melatonin production, reducing sleepiness
• What happens during jet lag in relation to pacemakers?

  Conflict between external cues and internal clock
• What is the primary endogenous pacemaker for the sleep/wake cycle?

  The suprachiasmatic nucleus (SCN)
• Where is the SCN located?

  In the hypothalamus within the limbic system
• What hormone does the pineal gland produce?

  Melatonin
• How does the SCN respond to light?

  It detects light and regulates melatonin production
• What is a free-running circadian rhythm?

  A rhythm maintained without external cues
• What did Siff's study in a cave demonstrate?

  The body clock can extend beyond 24 hours
• What criticism exists regarding Siff's study methodology?

  Participants controlled artificial light usage
• What did recent research by Caesar suggest about the endogenous pacemaker?

  It is capable of a precise 24-hour rhythm
• What evidence supports the SCN as the endogenous pacemaker?

  Ralph's study with mutant hamsters
• What happened when Ralph replaced the SCN of mutant hamsters?

  They adopted a normal 24-hour rhythm
• What are the implications of understanding circadian rhythms?

  Improved treatments for jetlag and productivity
• How can knowledge of circadian rhythms benefit health services?

  By timing drug treatments effectively
• What are the effects of blue light exposure at night?

  It disrupts the biological clock and sleep
• What did Miles' research on a blind man reveal?

  He had a circadian rhythm of 24.9 hours
• What is chronobiology?

  The study of biological rhythms
• How do some species adapt their circadian rhythms?

  They can turn off rhythms when not needed
• What is a unique behavior of arctic reindeer regarding circadian rhythms?

  They lose their circadian rhythm in summer
• What is the significance of the study of circadian rhythms?

  It helps understand biological processes in various species