Sleep + consciousness

Question 1

When might you see a high frequency, low amplitude signal on an EEG? When might you see a high amplitude signal on an EEG?

Answer 1

High frequency, low amplitude = normal waking

High amplitude = during seizure –> full consciousness is lost

Question 2

What would be seen on an EEG if the neurones were firing out of phase?

Answer 2

Low amplitude, desynchronised signals

**in phase = high amplitude “slow wave” appearance

Question 3

What does synchronous signals/firings on a EEG represent?

Answer 3

This is ABNORMAL

more synchronisation = less conscious

Question 4

Where is melatonin released from?

Answer 4

Pineal gland (posterior border of the 3rd ventricle)

Question 5

What does melatonin do?

Answer 5

Free radical scavenger –> removes/neutralises free radicals that have accumulated during waking

Question 6

where are the key control centres for sleep and wakefulness located?

Answer 6

Reticular formation of the pons

Question 7

Around which nuclei is the BBB “leaky”?

Answer 7

medial and ventrolateral preoptic nuclei

Question 8

What effect do Ghrelin + leptin have on sleep?

Answer 8

Ghrelin = inhibits sleep 
Leptin = increases sleepiness

Question 9

Where are the histaminergic neurones contained? What is their state during wakefulness and sleep?

Answer 9

Located in the tuberomamillary nucleus (projection from preoptic nucleus)
These neurones are active during waking and silent during all stages of sleep

Question 10

What condition can antihistamines be used to treat? Give examples of such drugs.

Answer 10

Insomnia (inhibit the H1, H2 and H3 receptors)

examples: diphenhydramine + doxylamine

Question 11

What neurotransmitters are released upon stimulation by orexin? Where are these neurotransmitters released from?

Answer 11

Acetylcholine - released from pedunculopontine nucleus (project to thalamus)
Noradrenaline - released from locus coeruleus
Serotonin - raphe nuclei
Dopamine - ventral tegmental area

Question 12

What is the level of activity of the noradrenergic neurones during sleep?

Answer 12

Low

Question 13

How does the level of activity of the acetylcholine system different during slow-wave sleep and REM sleep?

Answer 13

Slow-wave sleep –> ACh activity is low

REM sleep –> activity of ACh neurones increases to near waking levels

Question 14

What is the level of activity of serotonin neurones during sleep?

Answer 14

These neurones completely stop

**LMNs are paralysed during sleep –> serotonin activity maintains the connection between the UMNs and LMNs

Question 15

What are the functions of REM sleep?

Answer 15

1. Memory consolidation
   - encode and consolidate LT memory
   - retrieve recent experiences form LT memory, relive them in a dream and store them again = strengthen neuronal connections
2. Removing junk + defragmenting memories
   - removing unwanted memories
3. Coping with stress
   - REM sleep increases before and after stressful experiences

Question 16

What effects can SSRIs have on sleep?

Answer 16

Maintain constantly high serotonin levels 24 h/d = interfere with REM sleep initiation + function
SSRIs often produce increased sleep onset latency and increase arousal = reduced sleep efficiency

Question 17

What effects can TCAs and MAOIs have on sleep?

Answer 17

TCAs = promote sleep
MAOIs = reduce sleep --> due to increased NA, DA and 5-HT levels

Question 18

How does sleep apnea occur?

Answer 18

Occurs when the motor disconnection during REM fails to avoid the respiratory system = stop breathing/weakened breathing
In most cases the muscles of the throat relax too much