Physiology of Sleep

Question 1

Characteristics of N-REM sleep

Answer 1

• Stages of sleep w/out REM (rapid eye movements)
• involved in brain and body regeneration
• 3 types =
  
  • N1
  • N2
  • N3 Slow Wave Sleep (SWS).

Question 2

Characteristics of slow wave sleep

Answer 2

• high amplitude slow brain waves
• increased arousal threshold compared to wake
• decreased muscle activity
• slow rolling eye-movements
• decreased heart rate, respirations and metabolism.

Question 3

Characteristics of REM sleep

Answer 3

• Rapid Eye Movement sleep → occurs every 90 minutes in adults.
• EEG looks like awake EEG but arousal threshold is higher than in NREM sleep.
• Muscles are paralyzed, except for eyes, middle ear & diaphragm.
• Dreams most often occur during this period, though they also occur during SWS

Question 4

Physiologic response of body during REM sleep

Answer 4

• active brain + paralyzed body
• temperature regulation is suspended (poikilothermic)
  
  • brain temperature rises
• engorgement of clitoris and penis
• heart and respiration become irregular.

Question 5

NTs involved in wakefulness

Answer 5

• ACH, Histamine, NE, 5HT, DA, Hypocretin
• Hypocretin stabilizes awake and is often absent in narcolepsy.
• Adonosine builds up in basal forebrain during wakefulness, falls with sleep.
  
  • Caffeine inhibits adenosine somehow.

Question 6

NTs involved in sleep/wake switch

Answer 6

• @ hypothalamus:
  
  • GABA
  • histamine
  • hypocretin
• major role in the control of the transition from wakefulness to sleep (sleep/wake switch).

Question 7

Major NTs involved in NREM sleep

Answer 7

• GABA and Galanine
• GABA and Galanine from anterior hypothalamus and elsewhere (including from thalamic reticulum) closes thalamus, synchronizes EEG, generates sleep spindles
• Delta waves (slow-wave sleep) are thought to come from the thalamo-cortical cells and cortex.

Question 8

Major NTs involved in REM sleep

Answer 8

• ACh
• low GABA and Galanine
• DA
• hypocretin (possible activity)

Question 9

Roles of process C & process S

Answer 9

• Process C = circadian rhythm
  
  • Circadian alerting system is linked to core body temperature.
• Process S = homeostatic system
  
  • Homeostatic system is linked to adenosine buildup @ basal forebrain

Question 10

Impacts of process C/process S on wake and sleep

Answer 10

• Sleepiness waxes and wanes as the circadian alerting system interacts with the homeostatic system (process S) in 24+ hour cycles independent of sleep periods.
• The circadian alerting system oscillates regardless of external clues
• During wake: adenosine builds up (process S) and circadian alerting system increases (↑ body temp) increase until just before you go to sleep.

Question 11

Key structures involved in wakefulness/sleep

Answer 11

• basal forebrain
  
  • adenosine accumulate during wake, reduced during sleep
• hypothalamus
  
  • sleep/wake switch
• SCN
  
  • circadian clock
• brainstem
  
  • ascending cortical activation
  • REM/SWS switch
• thalamus
  
  • gateway of sensory info to cortex
  • generates spindles, slow wave sleep