76 - Sleep

Question 1

Alpha waves

Answer 1

(8 - 13 Hz)

a. associated with state of relaxed wakefulness in an adult with their eyes closed
b. prominent over occipital and parietal areas
c. EEG changes to beta rhythm if eyes open or in response to other sensory stimuli. Mental concentration such as that required to do arithmetic problems will also cause a change to the beta rhythm.

Question 2

Beta waves

Answer 2

(13 - 30 Hz)

a. smaller amplitude than alpha waves
b. sometimes called desynchronized EEG
c. normally seen over frontal region
d. also found over other regions during intense mental activity

Question 3

Theta waves

Answer 3

(4 - 7 Hz)

Question 4

Delta waves

Answer 4

(0.5 - 3.5 Hz)

Question 5

Which waves are associated with stages of sleep in a healthy adult?

Answer 5

Both theta and delta activity are associated with stages of sleep in a healthy adult

Question 6

What are the stages of sleep?

Answer 6

1. Stage 1 - transition awake – asleep; theta waves prominent
2. Stage 2 - light sleep, K complexes and sleep spindles
3. Stage 3 - moderately deep sleep some delta waves (more than 20% less than 50%)
4. Stage 4 - deep sleep - delta waves more than 50% of period.

Note:

• Stage 3 - 4 sleep sometimes grouped together as slow wave sleep or deep sleep or stage delta NREM sleep
• Above 4 stages called Non - REM sleep.
• REM or rapid eye movement sleep

Question 7

Describe the awake to sleep transition

Answer 7

1. Awake and alert with eyes open – beta waves
2. Awake but relaxed with eyes shut – alpha waves
3. Enter stage 1 sleep

Question 8

Describe non-REM sleep

Answer 8

1. Brain uses less oxygen than when awake or in REM sleep.
2. decreased body temperature and metabolic rate
3. decreased heart rate and blood pressure
4. decreased respiratory rate
5. Muscles relaxed but major postural adjustments made about every 20 minutes.
6. Threshold for arousal increases as EEG wave frequency decreases. So it is harder to arouse sleeper in Stage 4 sleep than Stage 1.
7. The pulsatile release of growth hormone (GH) is related to the sleep wake cycle with more than 70% of GH released during the first half (mainly slow wave sleep) of a person’s nightly sleep.

Question 9

Describe REM sleep

Answer 9

1. Also called paradoxical sleep since EEG similar to awake EEG. Other names active sleep and desynchronized sleep.
2. PGO spikes (pontine - geniculate - occipital) associated with bursts of eye movements.
3. Irregular heart beat and respiration. Penile erection in males, clitoral engorgement in women.
4. Depressed muscle tone throughout body except for muscles moving eyes, and respiratory muscles. Intense postsynaptic inhibition of alpha motor neurons.
5. REM dreams are longer, and more visual and emotional than the thought-like dreams of non-REM sleep.

Question 10

How is REM sleep affected by alcohol?

Answer 10

REM rebound after suppression by alcohol, barbiturates or other REM suppressing drugs

Question 11

How is REM affected during the onset of puberty in females?

Answer 11

At the start of puberty in females, there is pulsatile release of gonadotropin from the pituitary during REM sleep. At maturation pulses occur throughout the day.

Question 12

Describe the normal sleep pattern in adults

Answer 12

Normal adult sleep pattern

a. Stage 4 sleep appears primarily in first half of sleep period
b. REM sleep does not usually occur until 90 minutes or more into sleep period.

Question 13

What controls the sleep-wake cycle?

Answer 13

Circadian rhythmicity is under homeostatic regulation

Question 14

Which nucleus of the hypothalamus is the “internal clock”?

Answer 14

Suprachiasmatic nucleus

Question 15

Describe the role of the suprachiasmatic nucleus

Answer 15

• Circadian clocks help animals adjust their physiology and behavior to the 24 hour day-night cycle. Body rhythms are synchronized (or photoentrained) to the day/night cycle which changes with the seasons. There is a photopigment melanopsin in special retinal ganglion cells projecting to the SNC. These retinal ganglion cells depolarize in response to light and are probably responsible for setting the “master” biological clock in the SCN.

Question 16

Where is melatonin synthesized and released?

Answer 16

Melatonin synthesis in the pineal gland is indirectly controlled by the suprachiasmatic nucleus.

Question 17

What is the role of melatonin in sleep?

Answer 17

Melatonin is a sleep promoting neurohormone that is thought to help modulate the brainstem circuits that control the sleep-wake cycle.

Question 18

What is epilepsy?

Answer 18

Epilepsy - disease characterized by tendency to have repeated seizures

Question 19

What are the classifications of epilepsy?

Answer 19

Several classification schemes for seizures and epilepsy

a. generalized seizure vs. partial (localized or focal) seizure
b. primarily generalized vs. secondary generalized

Question 20

What is grand mal epilepsy?

Answer 20

a. now called tonic - clonic seizures (new nomenclature)
b. patient losses consciousness during grand mal seizure
c. tonic period of increased muscle tone followed by
d. clonic period consisting of jerky movements
e. postictal state; period of confusion following the seizure that usually last ~ 5 to 30 minutes

Question 21

What is petit mal epilepsy?

Answer 21

a. now called absence seizures since transient loss of consciousness (usually just 5-10 seconds)
b. 3 per second spike and dome (or spike and wave) pattern seen on EEG during seizure
c. seizures begin in childhood and rarely persist through adolescence (Usually just in childhood for patients with normal intelligence and normal background activity on EEG)
d. Muscle tone is maintained so patient rarely falls.
e. Subtle motor manifestations such as eye blinking are common during the seizure.
f. no postictal state since full orientation found immediately after the seizure

Question 22

Grand mal and petit mal epilepsy are examples of which type of epilepsy?

Answer 22

Genealized epilepsy

Question 23

What are the two types of focal or partial epilepsy?

Answer 23

Simple partial or complex partial

Question 24

Describe a simple partial seizure

Answer 24

Simple partial seizures do not affect general consciousness.

• Example - Jacksonian motor seizures

Question 25

Describe a complex partial seizure

Answer 25

a. affect consciousness b. usually in temporal lobe or frontal lobe c. formerly called temporal lobe seizures or psychomotor seizures. d. Verbal and/or motor automatisms can occur. Motor automatisms may be simple oral behaviors (such as lip smacking, chewing) or manual automatisms (patting, picking at clothing). Complex motor automatisms such as cycling movements of the legs may also occur.

Question 26

What are the symptoms of narcolepsy?

Answer 26

a. Sleep attacks - principal symptom; associated with excessive daytime sleepiness b. Cataplexy - abrupt attack of muscle weakness and hypotonia triggered by an emotional stimulus c. Sleep paralysis d. Hypnagogic hallucinations - hallucinations at transitions between wakefulness and sleep e. Sleep - onset REM f. Decreased voluntary sleep latency

Question 27

What is the cause of narcolepsy?

Answer 27

Cause in humans – reduction or absence of hypothalamic cells that produce and secrete orexin (hypocretin). The loss of these cells is probably due to an autoimmune attack on the cells. There is probably a genetic susceptibility to narcolepsy which increases chance that certain infections will result in autoimmune attack on orexin/hypocretin cells.

Question 28

What is a parasomnia?

Answer 28

Parasomnias are a category of sleep disorders that involve abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep.

Question 29

What are some examples of parasomnias?

Answer 29

- Bed wetting or nocturnal enuresis - Sleep walking or somnambulism - Sleep terrors - REM sleep behavior disorder - Sleep apnea

Question 30

Describe sleep terrors

Answer 30

sleep terrors: occur during non-REM sleep, different from nightmares which are bad dreams in REM sleep

Question 31

Describe REM sleep behavior disorder

Answer 31

REM sleep behavior disorder is REM sleep without atonia or hypotonia

Question 32

Describe sleep apnea

Answer 32

Sleep apnea – at least 10 sec. pause in breathing during sleep a. central sleep apnea b. obstructive sleep apnea c. mixed apnea

Question 33

Why do we sleep?

Answer 33

Several different hypotheses have been proposed. Recent research shows that sleep can increase interstitial space in the brain and contribute to the removal of potentially neurotoxic waste products.

Question 34

What is another theory of why we sleep?

Answer 34

Another hypothesis is that sleep has an important role in learning and memory. Recent research showed that sleep has a key role in promoting learning-dependent synapse formation

Question 35

Which brain areas and neurotransmitters are closely associated with wakefulness?

Answer 35

- Cholinergic neurons of the pons-midbrain junction - Norepinephrine in the locus coeruleus - Serotonin in the pontine raphe neuron

Question 36

Describe the cholinergic neurons of wakefulness

Answer 36

Cholinergic neurons (of the pons-midbrain junction) are part of the reticular activating system. These neurons fire at high rates during waking and REM sleep but are quiet during non-REM sleep.

Question 37

Describe the locus coeruleus and pontine nuclei of wakefulness

Answer 37

The locus coeruleus and pontine nuclei are also active during wakefulness but they are not active during REM sleep.

Question 38

Describe histaminergic neurons in relation to sleep and wakefulness

Answer 38

Histaminergic neurons of the posterior hypothalamus (in the tuberomammillary nucleus (TMN)) are selectively active in the awake state. Antihistamine drugs which can cross the blood-brain barrier might promote sleep by blocking central histamine receptors responsible for arousal.

Question 39

Describe the role of orexin in promoting wakefulness

Answer 39

Certain neurons in the lateral hypothalamus which release orexin (also called hypocretin) excite the monoaminergic neurons in the locus coeruleus and raphe. These orexin neurons also promote wakefulness via their excitation of the histamine-containing neurons in the tuberomammillary nucleus.

Question 40

Describe the neurotransmitters that are active during the onset of sleep (NREM)

Answer 40

- Sleep onset is caused by decreased firing of the cholinergic, monoaminergic and histamine-containing neurons above. - Neurons in the VPLO (ventrolateral preoptic nucleus of the hypothalamus) periodically inhibit the above neurons and thus are involved in non-REM sleep onset.

Question 41

What generalization can we make regarding monoaminergic and cholinergic systems?

Answer 41

Both monoaminergic and cholinergic systems are active during the waking state and suppressed during non-REM sleep.

Question 42

What are sensory evoked potentials?

Answer 42

Potentials extracted from an EEG by use of computer averaging techniques - this requires repeated sensory stimuli

Question 43

What types of sensory evoked potentials can be tested?

Answer 43

- Brainstem auditory evoked potentials - Visual evoked potentials - Somatosensory evoked potentials (stimuli electrical stimulation of peripheral nerve - used during some spinal surgery)

Question 44

How are sensory evoked potentials clinically relevant?

Answer 44

Useful for evaluating demyelinating diseases such as multiple sclerosis.