Sleep (Lecture 10) Flashcards
What is sleep?
- a readily reversible state of reduced responsiveness to , and interaction with the environment
- not readily reversible:
- coma
- general anesthesia
- death
- —> these do not qualify as sleep
EEG (electroencephalogram
- general activity of the cerebral cortex
- fluctuations in voltage between any given 2 electrodes
- = excitation of cortical neurons
- because signal must penetrate so many layers of non neural tissue = thousands of neurons must fire in unison to generate visible signal
wakefulness and stages of sleep are characterized by…..
-different patterns of brain activity
Awake and Alert
- Beta activity
- 13-30 Hz
- desychronized
Awake and Relaxed
-Alpha activity
8-12 Hz
-increasing synchronicity
-more prevalent with eyes closed
Stage 1 Sleep
-theta activity
-3.5-7.5 Hz
-transition between sleep and wakefulness
eyelids slowly open and close and eyes roll up and down
LASTS ABOUT 10 minutes during first sleep cycle
Stage 2 Sleep
-some theta activity
-3.5-7.5 Hz
-sleep spindles
-12-14 Hz (beta-eque)
-short bursts 2-4 per minute
-K complexes
-sudden sharp waveforms
-1 per minute
-triggered by noises = mechanism to inhibit waking?
LASTS ABOUT !% minutes during first sleep cycle
Slow Wave sleep (SWS)
-Delta activity
< 3.5 Hz
-difficult to wake people from SWS and when awakened, report no dreaming, but may remember image or emotion
Stage 3 sleep
-some theta activity
-20-50% delta
~20 minutes in first sleep cycle
stage 4 sleep
-some theta activity
> 50% delta
-deepest sleep
~ 45 min in first sleep cycle
Delta Waves
-show oscillations of ~1 Hz
down state
- neurons are silent
- may reflect rest for cortical neurons
up state
-neurons show burst of activity that is highly synchronized
REM sleep
- theta activity (like stage 1,2,2)
- 3.5-7.5 Hz
- Beta activity (like wakefulness)
- 13-30 Hz
- Paradoxical Sleep
- people awakened easily from REM sleep and report vivid dreams
Paradoxical SLeep
-EEG shows desychronized brain activity reminiscent of wakefulness
Sleep Cycle
- sleep alternates between REM and nREM (stages 1-4) in 90 minute sleep cycles
- in avg. 8 hours of sleep you experience 4-5 bouts of REM sleep
- as night progresses stage 2 and REM sleep are prolonged and SWS is reduced
Stage 1 physiological changes
- muscle activity reduced
- occasional muscle twitch
Stage 2 Physiological changes
- breathing and heart rate slows
- decrease in body temperature
SWS Physiological changes
- slow rhythmic breathing
- limited muscle activity
REM Physiological changes
- rapid eye movement
- muscles relax
- breathing is rapid and shallow
- heart rate increases
- sexual tissue engorges