Sleep Flashcards
What is responsible for controlling the circadian rhythm of the sleep-wake cycle?
Suprachiasmatic nucles
What is melatonin secreted by and what is its function?
Pineal gland
Modulates brainstem circuits that govern sleep-wake cycle
Synthesis increases as light decreases
Describe the interaction between the SCN and melatonin
SCN produces alerting signals and opposes the sleep load
Melatonin attenuates the alterting signals from the SCAN, causing wakefulness to decrease and sleep to occur
When melatonin levels drop in the morning, alerting signals increase again
What is sleep gate?
Time of maximum sleep drive (homeostatic) and minimum circadian drive (wakefulness)
What stages comprise NREM sleep?
Stages 1-3
Describe stage 1 sleep
Drowsy period
Slightly lower frequency and higher amplitude EEG waves - theta waves
Describe stage 2 sleep
Presence of sleep spindles on EEG
K-complex about every two minutes
Describe stage 3 sleep
Slow wave sleep
Deepest level of sleep
Low frequency, high amplitude EEG - delta waves
Difficult to awake people
What physiological changes occur in NREM sleep?
Decrease in muscle tone, HR, breathing, BP, metabolic rate, temp
Reduced movement, but tossing and turning can occur
Sleepwalking and sleep talking
Describe REM sleep
EEG similar to awake state
Increase in BP, HR, metabolism
Dreaming
Large muscle paralysis
Newborns spend more time in this stage than adults
What is REM rebound?
If deprived of REM sleep, the individual will make up for it at the next opportunity by going directly into REM sleep
Describe the cycles of REM/NREM sleep
After REM, brain cycles back through NREM
N3 generally occurs in the second cycle, but not again
4-6 additional periods of REM sleep, every 90 ,imutes
REM duration increases with each cycle
What is the role of the reticular activating system during sleep?
Cholinergic neurons project to thalamocortical neurons
Active during waking and REM sleep, quiet during NREM
Active RAS stimulates cortex and PNS, which sends positive feedback signals to RAS
RAS stimulation causes awakening of sleeping animal
What is the role of the Thalamus in sleep?
Gates sensory information, blocks input during sleep
Patterned interaction between thalamus and cortex important for sleep
When stimulated, causes awake animal to fall asleep
What NTs are present in wakefulness?
Monoamines: DA, NE, 5-HT
ACh
Histamine
Orexin/hypocretin
