endogenous pacemakers & exogenous zeitgebers

• What are endogenous pacemakers?

  Internal body clocks regulating biological rhythms
• What did Folkard's study demonstrate about endogenous pacemakers?

  They struggled to adjust to a sped-up clock
• What is the menstrual cycle?

  Time from one period to the next
• How long does a typical menstrual cycle take?

  Approximately 28 days
• What hormone rises during ovulation?

  Oestrogen
• What happens if pregnancy does not occur after ovulation?

  The egg is absorbed, and menstruation occurs
• What is Seasonal Affective Disorder (SAD)?

  A psychological disorder with depressive symptoms
• What triggers SAD symptoms?

  Shorter daylight hours in winter
• How does melatonin affect serotonin levels?

  Melatonin disrupts serotonin levels, causing depression
• How many stages of sleep are there?

  5 stages
• What occurs during REM sleep?

  Body is paralyzed, but the brain is active
• What is the role of the SCN in biological rhythms?

  It regulates the sleep/wake cycle
• What did Decoursey et al. find in their study?

  Chipmunks lost their sleep/wake cycle
• What happened when SCN cells were transplanted in Ralph et al.'s study?

  Normal hamsters defaulted to a 20-hour cycle
• How can light act as an exogenous zeitgeber?

  It can reset the body's main pacemaker
• What did Campbell and Murphy demonstrate about light?

  Light can be detected by skin receptors