Sleep & Cortical States Flashcards
What is sleep?
is a natural, reversible, recurrent state of reduced responsiveness to external stimulation that is accompanied by complex and predictable changes in physiology
What is sleep characterized by?
altered consciousness
minimal motor & sensory activity
Specific pattern of brain activity
Reduced interactions with the external world
What is electroencephalography (EEG)?
EEG is an electrophysiological monitoring method to record electrical activity of the brain with electrodes placed along the scalp
What does EEG measure?
measures voltage currents resulting from electrical potentials generated by cortical neurons, reflected in the EEG as electrical waves; Brain waves
What is the EEG used for?
Monitor sleep stages and diagnose sleep disorders
Diagnose neurological disorders
Monitor coma, brain death and anesthesia level
When do the different brain waves show?
Beta: highly alert,, eyes open
Alpha: relaxed, eyes closed
Theta: Drowsy
Delta: deep sleep
What are the two states of wakefulness?
Active wakefulness: eyes open, active state
Resting wakefulness: eyes closed, relaxed state
What are the two states of sleep?
Non-rapid eye movement (non-REM) sleep
Rapid eye movement (REM) sleep
How many stages make up the non-REM sleep?
4 stages
Which brain waves are associated with each Sleep-Wake states?
Wakefulness: Beta & alpha (high EEG frequency, low EEG amplitude)
Stage 1: Theta (intermediate EEG frequency, intermediate amplitude)
Stage 2: theta and sleep spindle (high frequency, low amplitude)
Stage 3 & 4: Delta (low frequency, high amplitude)
REM sleep: Beta & alpha (high frequency, low amplitude
What happens during REM sleep?
rapid eye movement (eyelids closed)
minimal muscle tone, muscle atonia (paralysis)
transient muscle activity (jerky muscle activity)
Predominance of dreams
How long are sleep cycles?
period of each cycle is approx. 90 min
Non-Rem sleep is longer at beginning of night but as sleeper becomes more rested the duration of non-REM decreases
REM sleep is short at the beginning but becomes long at the ends
What is the ascending arousal system?
System that keeps the cerebral cortex and thalamus excited during wakefulness
What are the components of the ascending arousal system?
Brainstem (reticular formation, brainstem nuclei, locus coeruleus, dorsal raphe)
Hypothalamus (lateral hypothalamus, posterior hypothalamus)
Basal forebrain (acetylcholine neurons, glutamate neurons)
How do the cortical neurons keep the cerebral cortex and the thalamus awake during wakefulness?
Cortical neurons discharge APs with fast & irregular patterns which results in a low amplitude and fast frequency EEG activity “desynchronized EEG” activity
Keeps a higher muscle tone by stimulating the motor neurons in the spine
What happens during Non-REM sleep
inhibitory neurons located in the hypothalamus inhibit the neurons of the arousal system to promote sleep.
Cortical and thalamic neurons switch to a slow and rhythmic discharge pattern which results in a high amplitude and slow frequency EEG activity “synchronized EEG” activity
What happens during REM sleep with the ascending cholinergic activation?
During REM sleep the brainstem acetylcholine neurons are re-activated and send their ascending fibers to excite the thalamus and cortex, which results in fast cortical activity (desynchronized activity) similar to waking state
What happens during the descending cholinergic control of muscle atonia?
During REM sleep the brainstem acetylcholine neurons are re-activated and send their descending fibers to excite medullar and spinal inhibitory interneurons which in turn inhibit spinal motor neurons. inhibition of motor neurons leads to a significant decrease of muscle tone, muscle atonia
What is dreaming?
it is the subjective experience of imaginary images, sounds/voices, thoughts or sensations during sleep, usually involuntarily
Most dreaming occurs during REM sleep
The sleep-wake cycle is regulated by what two processes?
Process S (Homeostatic)
Process C (Circadian)
What is Process S?
sleep propensity accumulates across the day, the more the person stays awake, the more the sleep propensity is increased and vice-versa
What is process C?
biological clock, under the control of the hypothalamus. follows light-dark cycle, releases sleep-related hormones
What are sleeps functions?
Sleep functions are yet unclear but sleep is important for physical, cognitive and psychological well-being (vital function)
resting of body
restore natural balances among neuronal centers
accelerations of neural maturation
facilitation of learning and memory
Clearance of metabolic waste products generated by neural activity in the awake
Conservation of metabolic energy
Hormonal regulations
What is insomnia?
Non-REM sleep deficiency characterized by a perceived inability to fall and remain asleep at night
What is hypersomnia?
Is a wakefulness deficiency characterized by excessive daytime sleepiness.
What is narcolepsy?
Is a REM sleep dysfunction seen in form of sudden REM sleep onset from wakefulness and excessive daytime sleepiness. associated with cataplexy. caused by loss of orixin neurons
What is sleepwalking?
is a non-REM sleep dysfunction characterized by a partial arousal from non-REM sleep and performing activities that are usually performed during wakefulness
What is REM Sleep Behaviour Disorder (RBD)?
RBD is a REM sleep dysfunction characterized by excessive motor activity during REM sleep due to the loss of REM sleep atonia. Often a precursor of neurodegenerative disorders.
