Biological Clocks and Sleep Notes

Biological Clocks and Sleep

Biological Clocks

  • Internal rhythms occurring inside the brain on a regular basis.
  • Driven by timed chemical mechanisms in the thalamus, hypothalamus, and midbrain.
  • Master Clock:
    • Suprachiasmatic nucleus (SCN).
    • Regulates other clocks in the brain.
    • Controls activity, awareness, and biological rhythms.
    • Resets itself based on daylight or light.
    • Light entering through the eyes (even in individuals with imperfect vision or blindness) helps reset the clock.

Cave Experiment

  • College students lived in a cave with no clocks, no lights, and no knowledge of time.
  • Artificial light was available at will.
  • Participants were instructed to sleep only when tired.
  • Findings:
    • Individuals did not maintain a 24-hour cycle.
    • Most people cycled on a 24.75 to 25-hour cycle.
    • The sleep time shifted later each night.
    • This indicates that the suprachiasmatic nucleus regulates internal clocks according to the sun.

Types of Biological Rhythms

  • Infradian Rhythms:
    • Occur less frequently than once a day.
    • Examples: Female menstrual cycle (every 28 days), tooth pain, symptoms of depression, seasonal affective disorder (SAD).
    • May have some influence on behavior.
  • Circadian Rhythms:
    • Occur about once every 24 hours.
    • Primarily associated with sleep-wake cycle, body temperature, and jet lag (internal desynchronization).
    • Significantly affected in artificial environments without sunlight.
    • People tend to get jet lagged because they are not exposed to sunlight
  • Ultradian Rhythms:
    • Occur more frequently than once a day (e.g., every 90 minutes).
    • Examples: Daydreaming, nostril breathing cycle (alternating nostrils), stomach contractions, oral behavior, full-length movie features, REM sleep.
    • Nostril Breathing: People breathe in and out of only one nostril at a time, alternating about every 90 minutes.
    • Elisa's Example: The speaker conducted an experiment on his wife, Elisa, to determine if she cycles with Ultradian rhythms: Found she got hungry and wanted a snack/drink about exactly every 90 minutes
      • 5 something, ate dinner
      • 6:25/6:30 she was thirsty
      • 90 mins later she was snacky
    • Rapid Eye Movement (REM) Sleep: Discovered by a University of Chicago researcher studying his child's sleep. Occurs approximately every 90 minutes during sleep.

Sleep

  • High percentage of people are sleep deprived.

Unanswered Questions About Sleep

  • Why do we sleep more when we're young?
  • Why do some animals sleep more than others (or not at all)?
  • What neurotransmitters are involved in sleep?
  • Why is sleep necessary, and what is its function?

Functions of Sleep

  • Restorative function for the body.
  • Psychological restoration, including memory consolidation.
  • Shakespeare: Sleep knits up the raveled sleeve of care.
  • Tied to brain functioning:
    • Facilitates learning and memory.
    • Removes neurotoxins from the brain.

Animal Sleep

  • Animals with brains sleep.
  • Variations in sleep duration:
    • Cows, sheep, horses: 2-4 hours a night (some sleep while standing).
    • Possums, cats, raccoons sleep a long time.
    • Humans: On average about 8 hours

Sleep Apnea

  • People stop breathing while asleep.
  • Can occur hundreds of times a night.
  • Snoring is often a sign.
  • Increases risk for heart and other body problems.

EEGs and Brain Waves

  • Electroencephalograms (EEGs) are used to measure electrical patterns in the brain.
  • Beta waves: Occur when awake and attentive.
  • Brain activity varies based on attention and state of mind.
  • Hypnagogic State: The transition from awake to asleep.
    • This shift feels pleasurable but can involve jerky movements (hypnic jerk).
    • The brain dislikes body movements it doesn't control, leading to sensations of falling or reaching out.