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.