Sleep-Wake Cycle And Disorders Flashcards
Rapid eye movement (REM) sleep
paradoxical sleep
Period of de-synchronized EEG activity during sleep
- rapid eye movements
- muscular paralysis of major muscle groups occurs (cant roll over but peripheral muscles may move)
- *classical dreaming occurs here
- penile/clitoral tumescence
Physiological effects:
- loss of motor tone
- increased brain oxygen use
- BP/pulse changes (usually gets higher, but can be higher in pathology or drugs. Gets lower in Non-REM sleep)
- increased ACh
- is believed to be the site of memory formation
starts with occurrence every 90 minutes of sleep and increases throughout the night
Non-REM sleep
Synchronized EEG activity. 4 stages and is the deepest form of sleeping
4 stages:
1) awake:
- open eyes = beta waves
- closed eyes = alpha waves
- both are very low amplitude but high frequency
2) N1 sleep:
- Light sleep and produces theta waves
3) N2 sleep:
- produces sleep spindles and K-complexes
- *site of bruxism occurring during sleep
4) N3 sleep
- deepest non-rem sleep
- delta waves (high amplitude, low frequency)
- *site of sleep walking, night terrors and bed wetting “wee and flee”
characteristics:
- slow waves
- moderate muscle tones (can roll over)
- slow/absent eye movements
- NO genital activity
- less dreaming
What are used to measure sleep?
EEG
Electromyogram
- measuring muscle paralysis
Electrooculogram
- detects eye movements
Major differences between REM and non-REM sleep
REM:
- beta waves
- lack of muscle tone
- rapid eye movements
- penile erection or vaginal secretion
- dreams occur
Non-REM (slow-wave sleep)
- theta/delta waves
- moderate muscle tone
- slow or absent eye movements
- no genital activity
- less dreaming and more nightmares/night terrors
What stage is the most common stage to be in throughout the night while sleeping?
REM sleep (25%)
What is the most common non-REM sleepover stage while sleeping?
N2 (45%)
How does REM sleep change over the course of a lifetime?
Decreases
- starts at 50% in newborns with total of 16 hrs on average
- adults (20s) = 20% with total of 8hrs on average
- elderly (60-70) = 15% with total of 6 hrs on average
common that stage 4 sleep just completely disappears in elderly populations
What is the key structure required for control of circadian rhythm?
The suprachiasmatic nucleus (SCN) area of the hypothalamus
- located just above the optic chiasm
Contains the biological clock that is responsible for organizing many of the body’s circadian rhythms
Pineal gland function in circadian rhythm
Endocrine gland that produces melatonin (serotonin-derived hormone)
- modulates sleep patterns
- production is triggered by darkness and fatigue
How does cortisol secretion work during sleep?
Decreases in 1st phase of sleep (N1)
Arises back up again once you begin to wake up
Reticular Activating System (RAS)
Neural circuit from the brain stem up to the thalamus that controls awakening and alertness
- uses NE as the primary transmitter
- damage to center = cant awaken = coma
- over stimulation = cant fall asleep
NE is associated with decreased REM sleep
Raphe nucleus
Serotonin neurons extending from raphe nucleus throughout the limbic system and forebrain
- primary neurotransmitter is serotonin
- active during sleep onset and begin to force someone into sleep
- serotonin neurons fire less as sleep prolongs, but is needed to both initate sleep and awaken someone from deep sleep -> REM sleep
- damage = cant fall asleep
- overstimulation = immediate sleep
holds almost all of the brains serotonergic neurons
Adenosine’s effect on sleep control
Neuromodulator that is released by neurons engaging in high levels of metabolic activity
- is believed to play a primary role in initiation of sleep (due to build up over the day)
caffeine is an antagonist of adenosine receptors = slows the build up of adenosine
ACh effect on sleep (dorsal pons/basal forebrain)
Long known to produce arousal and sleeplessness
- increase ACh in the dorsal pons and basal forebrain = desynchronization of the cortical regions of the cerebral cortex
- *increases REM sleep
Histamine effect in sleep
Originate in the hypothalamic tuberomammillary nucleus (TMN)
- promote and stabilize wakefulness and attention
- inhibts non-REM sleep
anti-histamines = sedation
Orexin (hypocretin-1)
Involved in wakefulness and auroral and produced in the hypothalamus
loss of orexin neurons causes narcolepsy