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.