Sleep & Cortical States

Question 1

What is sleep?

Answer 1

is a natural, reversible, recurrent state of reduced responsiveness to external stimulation that is accompanied by complex and predictable changes in physiology

Question 2

What is sleep characterized by?

Answer 2

altered consciousness
minimal motor & sensory activity
Specific pattern of brain activity
Reduced interactions with the external world

Question 3

What is electroencephalography (EEG)?

Answer 3

EEG is an electrophysiological monitoring method to record electrical activity of the brain with electrodes placed along the scalp

Question 4

What does EEG measure?

Answer 4

measures voltage currents resulting from electrical potentials generated by cortical neurons, reflected in the EEG as electrical waves; Brain waves

Question 5

What is the EEG used for?

Answer 5

Monitor sleep stages and diagnose sleep disorders
Diagnose neurological disorders
Monitor coma, brain death and anesthesia level

Question 6

When do the different brain waves show?

Answer 6

Beta: highly alert,, eyes open
Alpha: relaxed, eyes closed
Theta: Drowsy
Delta: deep sleep

Question 7

What are the two states of wakefulness?

Answer 7

Active wakefulness: eyes open, active state
Resting wakefulness: eyes closed, relaxed state

Question 8

What are the two states of sleep?

Answer 8

Non-rapid eye movement (non-REM) sleep
Rapid eye movement (REM) sleep

Question 9

How many stages make up the non-REM sleep?

Answer 9

4 stages

Question 10

Which brain waves are associated with each Sleep-Wake states?

Answer 10

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

Question 11

What happens during REM sleep?

Answer 11

rapid eye movement (eyelids closed)
minimal muscle tone, muscle atonia (paralysis)
transient muscle activity (jerky muscle activity)
Predominance of dreams

Question 12

How long are sleep cycles?

Answer 12

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

Question 13

What is the ascending arousal system?

Answer 13

System that keeps the cerebral cortex and thalamus excited during wakefulness

Question 14

What are the components of the ascending arousal system?

Answer 14

Brainstem (reticular formation, brainstem nuclei, locus coeruleus, dorsal raphe)
Hypothalamus (lateral hypothalamus, posterior hypothalamus)
Basal forebrain (acetylcholine neurons, glutamate neurons)

Question 15

How do the cortical neurons keep the cerebral cortex and the thalamus awake during wakefulness?

Answer 15

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

Question 16

What happens during Non-REM sleep

Answer 16

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

Question 17

What happens during REM sleep with the ascending cholinergic activation?

Answer 17

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

Question 18

What happens during the descending cholinergic control of muscle atonia?

Answer 18

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

Question 19

What is dreaming?

Answer 19

it is the subjective experience of imaginary images, sounds/voices, thoughts or sensations during sleep, usually involuntarily
Most dreaming occurs during REM sleep

Question 20

The sleep-wake cycle is regulated by what two processes?

Answer 20

Process S (Homeostatic)
Process C (Circadian)

Question 21

What is Process S?

Answer 21

sleep propensity accumulates across the day, the more the person stays awake, the more the sleep propensity is increased and vice-versa

Question 22

What is process C?

Answer 22

biological clock, under the control of the hypothalamus. follows light-dark cycle, releases sleep-related hormones

Question 23

What are sleeps functions?

Answer 23

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

Question 24

What is insomnia?

Answer 24

Non-REM sleep deficiency characterized by a perceived inability to fall and remain asleep at night

Question 25

What is hypersomnia?

Answer 25

Is a wakefulness deficiency characterized by excessive daytime sleepiness.

Question 26

What is narcolepsy?

Answer 26

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

Question 27

What is sleepwalking?

Answer 27

is a non-REM sleep dysfunction characterized by a partial arousal from non-REM sleep and performing activities that are usually performed during wakefulness

Question 28

What is REM Sleep Behaviour Disorder (RBD)?

Answer 28

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.