Module 23 REVIEW

• 23-1 What is sleep?

• Sleep is the periodic, natural loss of consciousness — as distinct from unconsciousness resulting from a coma, general anesthesia, or hibernation. (Adapted from Dement, 1999.)

• 23-2 How do our biological rhythms influence our daily functioning?

• Our bodies have an internal biological clock, roughly synchronized with the 24-hour cycle of night and day.
• This circadian rhythm appears in our daily patterns of body temperature, arousal, sleeping, and waking. Age and experiences can alter these patterns, resetting our biological clock.

• 23-3 What is the biological rhythm of our sleeping and dreaming stages?

• We cycle through four distinct sleep stages about every 90 minutes:
  • NREM-1 sleep is the brief, near-waking sleep with irregular brain waves we enter (after leaving the alpha waves of being awake and relaxed); hallucinations (sensations such as falling or floating) may occur.
  • NREM-2 sleep, in which we spend about half our sleep time, with its characteristic sleep spindles (bursts of rhythmic brain waves).
  • NREM-3 sleep is deep sleep, in which large, slow delta waves are emitted.
  • REM (rapid eye movement) sleep is described as a paradoxical sleep stage because of internal arousal but external calm (near paralysis). It includes most dreaming and lengthens as the night goes on.
• During a normal night’s sleep, NREM-3 sleep shortens and REM and NREM-2 sleep lengthens.

• 23-4 How do biology and environment interact in our sleep patterns?

• Biology — our circadian rhythm as well as our age and our body’s production of melatonin (influenced by the brain’s suprachiasmatic nucleus) — interacts with cultural expectations and individual behaviors to determine our sleeping and waking patterns.
• Being bathed in (or deprived of) light disrupts our 24-hour biological clock. Night-shift workers may experience a chronic state of desynchronization.

• 23-5 What are sleep’s functions?

• Sleep may have played a protective role in human evolution by keeping people safe during potentially dangerous periods.
• Sleep also helps restore and repair damaged neurons.
• Sleep consolidates our memories by replaying recent learning and strengthening neural connections.
• Sleep promotes creative problem solving the next day.
• During slow-wave sleep, the pituitary gland secretes a human growth hormone necessary for muscle development.

Multiple-Choice Questions

1. Which of the following represents a circadian rhythm?
   1. A burst of growth occurs during puberty.
   2. The sleep cycle is roughly 90 minutes long.
   3. Our bodies sleep-wake on a roughly 24 hour schedule.
   4. Our bodies become paralyzed when we enter REM sleep.
   5. Pulse rate increases when we exercise.
2. Shortly after falling asleep, James experiences the hypnagogic sensation of falling. It is most likely that he is in which stage of sleep?
   1. Alpha
   2. NREM-1
   3. NREM-2
   4. NREM-3
   5. REM
3. What is the role of the suprachiasmatic nucleus in sleep?
   1. It induces REM sleep every 90 minutes.
   2. It causes the pineal gland to increase the production of melatonin.
   3. It causes the pituitary gland to increase the release of human growth hormone.
   4. It causes the pituitary gland to decrease the release of human growth hormone.
   5. It causes the pineal gland to decrease the production of melatonin.
4. Which of the following sleep theories would best explain why athletes perform better after a full night’s sleep?
   1. Memory
   2. Protection
   3. Growth
   4. Recuperation
   5. Creativity
5. Patrick has just entered REM sleep. Which of the following is he likely to experience?
   1. Body paralysis
   2. The sensation of falling
   3. Delta waves
   4. Alpha waves
   5. Sleep spindles

Practice FRQs

1. Researchers have identified the brain waves associated with waking and sleeping stages. Explain which stage a person is in if researchers detect the following brain waves:
   • Alpha waves
   • Sleep spindles
   • Delta waves

Answer

1 point: Alpha waves are present in an awake, relaxed state just before falling asleep. Page 232

1 point: Sleep spindles appear during NREM-2 sleep. Page 234

1 point: Delta waves appear during our deepest stage of sleep, NREM-3. Page 234

2. A friend believes that sleep is not that important and that he can go several days without sleep with no ill effects. Use the following theories about why we sleep to explain some negative effects your friend might experience after missing a couple nights of sleep:
   • Sleep helps us recuperate.
   • Sleep helps us restore memories.
   • Sleep supports growth.

(3 points)