Sleep Flashcards

1
Q

What three techniques are used to monitor activity during sleep?

A

Electroencephalography (EEG)
Electromyography (EMG)
Electrooculography (EOG)

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2
Q

Describe the EEG and EMG activity in wakefulness.

A

EEG – fast brain rhythm – beta waves (~30 Hz)

EMG – reasonable amount of muscle tone because you are maintaining posture and ready for action

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3
Q

Describe the EEG, EMG and EOG activity in non-REM sleep.

A
Stage 1+2 
 Light sleep
 EEG – theta (4-8 Hz) waves – gradually becoming more and more drowsy
 EOG – NO eye movements 
 EMG – muscle activity reduced considerably 
Stage 3+4 
 Very deep sleep
 EEG - Delta activity (< 4 Hz)
 EOG – minimal eye movement
 EMG – continued relaxation of muscles
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4
Q

Describe the EEG, EMG and EOG activity in REM sleep.

A

EEG – brain shifts abruptly back to fast rhythm (similar to wakefulness)
EOG – rapid eye movement
EMG – muscle activity at its lowest – subject is basically paralysed

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5
Q

How long is a normal sleep cycle?

A

approx 90mins

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6
Q

Compare the relative amounts of NREM and REM sleep in a sleep cycle at the start of a night’s sleep and at the end.

A

Start of the night – more NREM sleep

End of the night – more REM sleep

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7
Q

Describe how heart rate and respiratory rate change during sleep.

A

SLOW during NREM

FAST during REM sleep

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8
Q

Which system is responsible for maintaining consciousness?

A

Reticular activating system

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9
Q

How does the reticular activating system control the activity of the cortex?

A

Either via direct connections

Or via indirect connections through the intralaminar nuclei of the thalamus

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10
Q

What are the two important nuclei in the hypothalamus that are responsible for influencing the reticular activating system and, hence, regulating the sleep-wake cycle?

A

Lateral Hypothalamus – excitatory
Ventrolateral Preoptic Nucleus – promotes sleep
NOTE: they have an antagonistic relationship

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11
Q

Describe the circadian synchronisation of the sleep-wake cycle.

A

The suprachiasmatic nucleus is responsible for synchronising the sleep-wake cycle with falling light level
It receives an input from the retina (not from the usual photogenic cells) and as light level falls the suprachiasmatic nucleus becomes more active

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12
Q

Describe the effect of the suprachiasmatic nucleus on the nuclei within the hypothalamus.

A

Falling light level –> increased activity of suprachiasmatic nucleus
This leads to activation of ventrolateral preoptic nucleus and inhibition of lateral hypothalamus so you become sleepier

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13
Q

What other important projection does the suprachiasmatic nucleus have and what is the importance of this projection?

A

Projection to the pineal gland
Increase in suprachiasmatic nucleus activity leads to activation of pineal gland so that it releases melatonin
Melatonin adjusts various physiological processes in the body that fit with sleep

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14
Q

What are some consequences of sleep deprivation?

Categorise them into

  1. Psychiatric and neurological
  2. pure neurological
  3. somatic
A

Psychiatric and neurological:
– Sleepiness, irritability, stress, mood fluctuations, depression,
impulsivity, hallucinations

neurological:
– Impaired attention, memory, executive function
– Risk of errors and accidents
– Neurodegeneration (?)

Somatic:
– Glucose intolerance
– Reduced leptin/increased appetite
– Impaired immunity
– Increased risk of cardiovascular disease and cancer
– Death
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15
Q

Describe three ways in which sleep is regulated after sleep deprivation.

A

Reduced latency of sleep onset (fall asleep faster. Sleep onset latency= speed of falling asleep)
Increased NREM sleep (sleep for longer)
Increased REM sleep (after selective REM sleep deprivation)

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16
Q

During what stages of sleep can you dream?

A

Both NREM and REM but you tend to dream more and are able to recall dreams better during REM sleep

17
Q

Describe the brain activity of the limbic system compared to the frontal lobe in sleep.

A

Brain activity in the limbic system is higher than in the frontal lobe
This is because the content of dreams tends to be more emotional thanin real life

18
Q

Sleep is important in memory consolidation. What is the difference in memory consolidation between NREM and REM sleep?

A

NREM – declarative = facts and events

REM – procedural = learning skills

19
Q

State some causes of insomnia that are physiological or due tobrain dysfunction.

A

Physiological – sleep apnoea, chronic pain

Brain Dysfunction – depression, fatal familial insomnia

20
Q

Hypnotics can be used to treat insomnia. How do they work?

A

They enhance the inhibitory (GABAergic) circuits in the brain

21
Q

What is narcolepsy?

A

A condition characterised by an extreme tendency to fall asleep whenever in relaxing surroundings

22
Q

What is cataplexy?

A

Sudden onset of muscle weakness that may be triggered by excitement or emotion. It is a symptom of narcolepsy

23
Q

Explain a feature of the sleep cycle of narcolepsy patients

A

Patients go straight to REM sleep without going through NREM sleep

24
Q

What is narcolepsy caused by?

A

Orexin deficiency
Orexin is a neuropeptide, which is the neurotransmitter in the lateral hypothalamus
Orexin deficiency could be autoimmune or genetic
Manage with tight control of sleep

25
Q

What are the potential consequences of working night shifts?

A

Physiological processes could become desynchronised

This can lead to sleep disorders, fatigue and increased risk of some conditions such as obesity, diabetes and cancer