sleep and cortical states Flashcards
sleep definition
is a natural, reversible, recurrent state of reduced responsiveness to external stimulation that is accompanied by complex
and predictable changes in physiology
sleep is characterized by
-Altered consciousness.
-Minimal motor & sensory activity.
-Specific pattern of brain activity.
-Reduced interactions with the external world.
whats EEG
Electroencephalography(EEG) is an electrophysiological monitoring method to record electrical activity of the brain, with electrodes placed along the scalp
EEG measures voltage currents resulting from electrical potentials (EPSP&IPESP) generated by _____ neurons, reflected in the EEG as electrical waves: ___ waves (_, __ , ___, ___ waves)
cortical
brain
α, β, θ, δ
EEG is used to
Monitor sleep stages & diagnose sleep disorders (Polysomnography)
Diagnose neurological disorders (e.g.epilepsy, encephalopathies, stroke…)
-Monitor coma, brain death and anesthesia level
characteristics of beta waves
highly alert, eyes open= low amplitude and high frequency
characteristics of alpha waves
relaxed, eyes closed= low amplitude and high frequency
characteristics of delta waves
deep sleep= high amplitude and low frequency
characteristics of theta waves
drowsy= high amplitude and low frequency
what are the 2 states of wakefulness
-active wakefulness: eyes open, active state
-resting wakefulness: eyes closed, relaxed state
what are the 2 states of sleep
-non-rapid eye movement sleep (non-REM)
-rapid eye movement (REM) sleep
EEG recording for wakefulness
Beta & Alpha waves: high EEG frequency (9–30 Hz) & low EEG amplitude
EEG recording for Stage I
Theta waves: intermediate EEG frequency (5–8 Hz) & intermediate EEG amplitude (50 – 100 μV) and K-Complex (isolated slow wave)
EEG recording for stage II
Theta waves and sleep spindle: high EEG frequency (11–15 Hz) & low EEG amplitude (50 μV).
EEG recording for stage III &IV
slow waves (delta waves): low frequency (0.5 to 4 Hz) & high EEG amplitude (100 – 150 μV)
EEG recording for REM sleep
Beta & Alpha waves: high EEG frequency (9–30 Hz) & low EEG amplitude (∼30 μV). The same as in Wakefulness.
REM sleep (paradoxical sleep) frequency, amplitude, eyelids, m. tone, m. activity, predominance of what)
-High EEG frequency (10–30 Hz) & low EEG amplitude (∼30 μV), Beta & Alpha waves. The same as in wakefulness
-Rapid eye movements (REM): eyelids closed,
-Minimal muscle tone, muscle atonia (i.e. muscle paralysis),
-Transient muscle activity (i.e. jerky muscle activity),
-Predominance of dreams.
sleep occurs in what kinds of cycles
The period of each cycle is approximately 90 minutes (1h & 1⁄2) in human (i.e. 4 – 5 cycles/night).
what decreases in non-REM sleep throughout the night
Non-REM sleep is longer at the beginning of the sleep but as the sleeper becomes more rested through the night, the durations of non-REM decrease.
when is REM sleep the shortest
REM sleep is short at the beginning but becomes long at the end
During wakefulness the cerebral cortex and thalamus are kept excited by neurons of the _____ ______ System located at
the subcortical level
ascending arousal
what neurons of the ascending arousal syst are in the brainstem
Reticular Formation (Glutamate neurons)
Brainstem nuclei (Acetylcholine neurons)
Locus Coeruleus (Noradrenaline neurons)
Dorsal Raphe (Serotonin neurons)
what neurons of the ascending arousal syst are in the hypothalamus
Lateral Hypothalamus (Orexin neurons)
Posterior Hypothalamus (Histamine neurons)
what neurons of the ascending arousal syst are in the basal forebrain
Acetylcholine neurons Glutamate neurons
During wakefulness the cortex and thalamus are kept excited by
neurons of the Ascending Arousal System located at the subcortical level.
Cortical neurons discharge APs with ___ & _____ patterns (i.e. not at the same time), which results in a ___ amplitude and ____ frequency EEG activity: ‘_____ EEG’ activity (i.e. beta & alpha waves).
fast & irregular
low
fast
desynchronized
The arousal system neurons stimulate also motor neurons in the spinal cord to keep a ____ muscle tone during wakefulness.
higher
during non-REM sleep, inhibitory neurons (mainly GABA) inhibit what to promote sleep
inhibit the neurons of the arousal sys
what is dreaming
Dreaming is the subjective experience of imaginary images, sounds/voices, thoughts or sensations during sleep, usually involuntarily (i.e. outside the control of the dreamer).
most of dreamings occur during what
REM sleep
do animals dream and what is their subjective experience
Dreaming occurs in animals as well. Animals certainly undergo REM sleep, but their subjective experience is difficult to determine
what 2 processes regulate sleep-wake cycle
process S (sleep homeostatic) and process C (circadian)
what is process S
(Sleep Homeostatic): sleep propensity (i.e. sleep need) accumulates across the day:
-The more the person stays awake, the more the sleep propensity incerased.
-The more the person stays asleep, the more the sleep propensity decerased.
what is process C
biological clock, under the control of the hypothalamus:
-Follows the light-dark cycle. affect
-Releases sleep-related hormones (e.g. Melatonin)
sleep is important for what
physical, cognitive and psychological well-being
what are the functions of sleep
-Resting of different parts of the body.
-Restore natural balances among the neuronal centers.
-Acceleration of neural maturation (need of sleep for youth).
-Facilitation of learning and memory (neuronal plasticity).
-Clearance of metabolic waste products generated by neural activity in the awake.
-Conservation of metabolic energy.
-Hormonal regulation.
-etc.
what is insomnia
is a Non-REM Sleep deficiency characterized by a perceived inability to fall and remain asleep at night, although it may not represent a true inability to
sleep (paradoxical insomnia = sleep state misperception)
what is hypersomnia
is a Wakefulness deficiency characterized by excessive daytime sleepiness. It is a failure in the activating of mechanisms that are necessary to maintain arousal during the day.
what is narcolepsy
is a REM sleep dysfunction seen in the form of sudden REM sleep onset from wakefulness (sleep attacks) and excessive daytime sleepiness. It is often associated with cataplexy (muscle paralysis) following a emotional reaction (e.g. fear, laugh). Caused by the loss of orixin neurons in the hypothalamus.
what is sleep walking (somnambulism)
is a Non-REM Sleep dysfunction characterized by a partial arousal (with low consciousness) from Non-REM sleep and performing activities that are usually performed during wakefulness (e.g. walking out of the room, eating, sex, driving, homicide…). A total amnesia of the event (i.e. do not recall the event).
what is REM sleep behaviour disorder (RBD)
is a REM sleep dysfunction
characterized by excessive motor activity during REM sleep due to the loss of REM sleep atonia. Patients act out the contents of their dreams. RBD is often a precursor to neurodegenerative diseases (e.g., Parkinson’s, Lewy body dementia…)
what is REM sleep behaviour disorder (RBD)
is a REM sleep dysfunction
characterized by excessive motor activity during REM sleep due to the loss of REM sleep atonia. Patients act out the contents of their dreams. RBD is often a precursor to neurodegenerative diseases (e.g., Parkinson’s, Lewy body dementia…)
