Biological Rhythms

• What is another name for circadian rhythms?

  The body clock
• Circadian rhythms operate on a 24-hour cycle which is reset by levels of light.
• What is an example of a circadian rhythm in humans?

  The sleep-wake cycle
• Exogenous zeitgebers are environmental events that can reset the body clock.
• The suprachiasmatic nuclei (SCN) in the hypothalamus detects the level of light present.
• Which hormone is associated with triggering sleep in response to decreased light levels?

  Melatonin
• Steps in the process of melatonin secretion and sleep onset

  1️⃣ Light levels decrease

  2️⃣ SCN detects decreased light

  3️⃣ Melatonin is secreted

  4️⃣ Sleepiness increases
• Once melatonin has been secreted, the sleep 'gate' opens, and sleep becomes inevitable, a state known as hypnagogic.
• What is influenced by melatonin secretion?

  Circadian rhythms
• Shift work and jet lag can lead to the desynchronization of circadian rhythms.
• Siffre's research in1973 involved spending two months in a cave deprived of light and sound.
• What was the duration of Siffre's circadian rhythm when he emerged from the cave?

  24-25 hours
• What did Folkard et al.'s research using a 22-hour sleep-wake cycle find?

  Problems with recall
• Siffre's study included only one participant, which is a limitation of his research.
• Siffre and other circadian rhythm research participants were exposed to artificial light during their procedures.
• What is an example of an infradian rhythm?

  The menstrual cycle
• Steps in the menstrual cycle

  1️⃣ Rising estrogen levels release an egg

  2️⃣ Egg travels to the oviduct

  3️⃣ Progesterone thickens the womb lining

  4️⃣ Menstruation occurs if the egg is not fertilized
• What condition is associated with the winter months and increased melatonin secretion?

  Seasonal affective disorder
• McClintock & Stern's research found that 68% of participants' menstrual cycles synchronised with their pad donor.
• Menstrual cycle synchronisation may have evolutionary advantages for tribes or clans.
• In which state did Rosen et al.'s research find the highest prevalence of winter SAD?

  New Hampshire
• Rosen et al.'s large-scale survey into SAD has good reliability due to its standardized questionnaire.
• What is one potential extraneous variable that could compromise McClintock & Stern's research?

  Pollution
• Large-scale surveys into SAD may lack explanatory power about why it occurs.
• Ultradian rhythms are cycles that occur in less than 24 hours.
• How many stages of sleep are there in an ultradian sleep cycle?

  Five
• Slow and rhythmic alpha waves are the first sign of sleep.
• Which type of brainwave is associated with deep sleep in stages 3 and 4?

  Delta waves
• REM sleep is the stage of sleep during which dreaming occurs according to research.
• REM stands for rapid eye movement, which indicates dreaming during sleep.
• Which stages of sleep are categorized as NREM sleep?

  Stages 1-4
• Who conducted groundbreaking research linking REM sleep and dreams?

  Dement & Kleitman
• Dement & Kleitman's findings showed a positive correlation between REM sleep and dreaming.
• Match the eye movement during REM sleep with the type of dream

  Vertical eye movements ↔️ Climbing ladders

  Horizontal eye movements ↔️ Throwing tomatoes
• Dement & Kleitman eliminated alcohol and caffeine intake to reduce confounding variables in their study.
• Dement & Kleitman's research had a small sample size of five participants, which limits generalizability.
• Dement & Kleitman's research may lack temporal validity due to being conducted in the 1950s.
• What type of eye movements occurred with dreams of climbing ladders or throwing basketballs in the air?

  Vertical eye movements
• Horizontal eye movements occurred with dreams of watching people throw tomatoes
• Dement & Kleitman eliminated alcohol and caffeine intake to avoid confounding variables in their sleep study.