D

Sleep and Sensation Lecture Notes

SLEEP

  • Sleep occurs in cycles lasting 90-120 minutes.
  • Each cycle consists of 4 stages:
    • NREM Stages (1-3):
    1. NREM 1:
      • Transitionary period (Alpha waves)
      • Very light sleep (10 minutes)
      • Awareness of sleeping is minimal.
    2. NREM 2:
      • Slightly deeper sleep (Theta waves)
      • Accounts for 25% of the night.
    3. NREM 3:
      • Deepest stage of sleep (Delta waves)
      • Responsible for physical restoration; decreases in duration as night progresses.
    • REM (Rapid Eye Movement):
      • Increases in length as the night continues; significant for cognitive functions such as dreaming and memory consolidation (first 10 minutes, extending up to 30-40 minutes by the end).
      • Vivid dreaming occurs, muscles are paralyzed to prevent acting out dreams.
      • Internally, the body is active while externally, the body is paralyzed (paradoxical sleep).

THEORIES OF SLEEP

  • Restoration Theory:
    • Sleep restores hormones, neurotransmitters, and energy.
    • Essential for muscle and brain tissue repair and recovery.
  • Cognitive/Information Processing Theory:
    • Supports memory consolidation of daily experiences, especially during REM sleep.
  • Energy Conservation Theory:
    • Suggests sleep evolved to save energy and protect during vulnerable periods.
    • The pineal gland releases melatonin, which regulates sleep-wake cycles.

SLEEP DISORDERS

  1. Insomnia:
    • Difficulty falling or staying asleep; prolonged symptoms meet diagnostic criteria.
    • Causes include irregular sleep schedules, pain, illness, and diet/medication.
    • Treatments vary based on the cause.
  2. Sleep Apnea:
    • Repeated cessation of breathing during sleep.
    • Symptoms include loud snoring and gasping. Types:
      • Obstructive: Relaxation of muscles blocks airway.
      • Central: Brain fails to signal appropriate muscles to breathe.
      • Complex: Combination of obstructive and central.
  3. Narcolepsy:
    • Characterized by uncontrollable sleep attacks and muscle paralysis (cataplexy).
    • Triggered by strong emotions; often genetic.
    • Treatments include wake-promoting medication.

VISION AND SENSATION

  • Anatomy of the Eye:
    • Components: Lens, pupil, retina, optic nerve.
    • Functioning: Cones detect color in the fovea while rods handle black-and-white vision across the retina.
  • Color Theories:
    1. Trichromatic Theory (Hermann von Helmholtz):
    • Three types of cones responsible for color perception (S-cone: blue, M-cone: green, L-cone: red).
    1. Opponent Processing Theory (Ewald Hering):
    • Colors are perceived through opposing pairs (e.g., Red-Green, Yellow-Blue).
  • Hearing Anatomy:
    • Outer Ear: Pinna, ear canal.
    • Middle Ear: Eardrum, ossicles (Hammer, Anvil, Stirrup).
    • Inner Ear: Cochlea, where transduction occurs.
  • Pitch Theories:
    • Place Theory: Different pitches are perceived depending on where sound waves stimulate the cochlea.
    • Frequency Theory: Frequency of neural firing corresponds to the pitch perceived.

PAIN AND BALANCE

  • Pain Perception:
    • Gate Control Theory suggests the spinal cord can prioritize sensory messages.
    • Differentiate between sharp (myelinated fibers) and dull pain sensations.
  • Balance & Kinesthetic Awareness:
    • Managed by the vestibular system, utilizing semi-circular canals to detect movement.
    • Provides feedback on body position and motion, which is essential to prevent dizziness and maintain equilibrium.