Sleep and Consciousness

Question 1

What are the different stages of consciousness according to the Glasgow Coma Scale (GCS)

Answer 1

Coma, unconsciousness, sleep, drowsy wakeful, normal wakeful and high arousal

Question 2

What is an EEG?

Answer 2

Electroencephalograph

Question 3

What does an EEG represent?

Answer 3

Consists of very small voltages that are recorded from the scalp and this represents the average activity of thousands of nerve cells

Question 4

What are EEGs commonly used for?

Answer 4

Detecting seizure activity and sleep/coma

Question 5

How does a coma present on an EEG?

Answer 5

No electrical activity to note

Question 6

Which structure coordinates sleep and wakefulness?

Answer 6

Reticular formation in the pons

Question 7

What are the 5 stages of sleep?

Answer 7

Normal sleep (four stages) and then REM sleep

Question 8

When is growth hormone mainly secreted?

Answer 8

In normal/slow-wave sleep

Question 9

How are cortisol levels affected by sleep?

Answer 9

Decrease during sleep

Question 10

Why does BP reduce during sleep?

Answer 10

Reduced sympathetic output

Question 11

How is leptin affected by sleep?

Answer 11

Leptin is released from fat cells during normal sleep which provides satiety

Question 12

How may sleep deprivation lead to perpetual hunger?

Answer 12

Leptin isn’t being secreted by fat cells to signal satiety

Question 13

What is the function of REM sleep?

Answer 13

Memory consolidation (short to long-term) and removing junk and defragmenting memories

Question 14

How long is a sleep cycle?

Answer 14

90 minutes

Question 15

Which molecules increase sleepiness in the body?

Answer 15

High CCK (satiety) and high adenosine levels

Question 16

Which molecules inhibit sleepiness in the body?

Answer 16

Increased ghrelin (hunger hormone) and low blood glucose

Question 17

How does caffeine keep us awake?

Answer 17

Caffeine antagonises A1 adenosine receptor to prevent sleepiness

Question 18

How do hunger hormones and adenosine affect our arousal and sleepiness?

Answer 18

Blood brain barrier is more permeable around the medial and ventrolateral pre optic nuclei in the thalamus so molecules can cross

Question 19

How do the pre-optic nuclei in the thalamus regulate sleep?

Answer 19

By modulating the activity of the tuberomamillary nucleus (TMN) histaminergic neurones

Question 20

What is the consequence of a lesion to the suprachiasmatic nucleus?

Answer 20

Destroys the diurnal sleep rhythm in animals

Question 21

Explain why we stay awake during the day and sleep at night (diurnal rhythm).

Answer 21

Suprachiasmatic nucleus lies above optic chiasm and receives input from the retina (specifically photoreceptors send action potentials constantly during daylight) which then project to the TMN

Question 22

What is narcolepsy?

Answer 22

Disorder due to abnormal sleep tendencies, excessive daytime sleepiness and pathological REM sleep

Question 23

What is thought to be the cause of narcolepsy?

Answer 23

Insufficient orexigens (appetite stimulants) due to autoimmune T-cell attack

Question 24

Where are orexigenic neurones located?

Answer 24

Posterior hypothalamus

Question 25

How do orexigens work to stimulate wakefulness?

Answer 25

From posterior hypothalamus project to brainstem nuclei to stimulate release of amine transmitters (acetylcholine, NA, serotonin and dopamine)

Question 26

When does sleep onset occur?

Answer 26

When the signals from preoptic nuclei (blood chemicals) and suprachiasmatic nucleus (day/light cycles) inhibit the histamine and orexin neurones to inhibit excitatory drive to monoamine neurones of pontine reticular formation

Question 27

In the context of the sleep/wake cycle: where are dopaminergic cells found?

Answer 27

Ventral tegmental area

Question 28

In the context of the sleep/wake cycle: where are cholinergic cells found?

Answer 28

Pedunculopontine nucleus

Question 29

In the context of the sleep/wake cycle: where are noradrenergic cells found?

Answer 29

Locus coeruleus

Question 30

In the context of the sleep/wake cycle: where are serotonergic cells found?

Answer 30

Raphe nuclei

Question 31

How is the cholinergic system affected by the sleep/wake cycle?

Answer 31

Decreased firing except for in REM sleep where ACh is released to allow activation of thalamus and cortex

Question 32

How is the noradrenaline system affected by the sleep/wake cycle?

Answer 32

Reduced firing in all sleep, implicated in why we don’t remember our dreams

Question 33

How is the dopaminergic system affected by the sleep/wake cycle?

Answer 33

Reduced firing in all forms of sleep

Question 34

Why are we paralysed in REM sleep?

Answer 34

Dopamine levels are low; nigrostriatal dopamine systems are required to activate the basal ganglia so that we can move (change motor programmes)

Question 35

How do amphetamines and cocaine prevent sleep?

Answer 35

Cause continual release of dopamine and noradrenaline

Question 36

How is the serotonergic system affected by the sleep/wake cycle?

Answer 36

Completely inactive in REM

Question 37

How does the serotonergic system create dreams?

Answer 37

Lack of serotonin activity means thalamus can’t transmit messages from sensory receptors to the cortex, so the cortex ‘freewheels’ and generates its own images and perceptions to create dreams

Question 38

How do SSRIs and SNRIs affect sleep?

Answer 38

Decrease in sleep efficiency and suppresses REM sleep

Question 39

How do tricyclic antidepressants affect sleep?

Answer 39

Promote sleep by blocking H1 and preventing noradrenaline uptake

Question 40

How do MAO inhibitors affect sleep?

Answer 40

Structurally similar to amphetamines so can cause insomnia

Question 41

How may insomnia be treated?

Answer 41

Antihistamines (nytol), benzodiazepines and Z drugs

Question 42

What is sleep apnoea?

Answer 42

When the motor innervation to the respiratory muscles ceases during REM sleep leading to airway obstruction –> individual wakes due to CO2 build up –> hyperventilation and agitation