Sleep

Question 1

What three techniques are used to monitor activity during sleep?

Answer 1

Electroencephalography (EEG) - evaluates electrical activity of brain. Electromyography (EMG) - electrical activity of muscle in response to stimulus. Electrooculography (EOG) - measuring the corneo-retinal standing potential that exists between front and back of human eye.

Question 2

What is the behavioural criteria for sleep?

Answer 2

Stereotypic or species-specific posture. Minimal movement Reduced responsiveness to external stimuli. Reversible with stimulation - unlike coma, anaesthesia or death.

Question 3

What are stages of sleep?

Answer 3

Stages 1 + 2 NREM Stages 3 + 4 NREM Stage 5 REM

Question 4

Compare psychological measurements during stage 1 + 2

Answer 4

Light sleep

EEG theta waves (4-8Hz) - gradually more and more drowsy

EOG - no eye movements

EMG - reduced muscle activity from wake

Question 5

Compare psychological measurements during stage 3 + 4

Answer 5

Very very deep sleep

EEG - delta activity <4Hz

EOG - minimal eye movement

EMG - continued relaxation of muscles

Question 6

Compare psychological measurements during stage 5

Answer 6

REM sleep

EEG - brain shifts abruptly back to fast rhythm similar to awake state

EOG - rapid eye movement

EMG - muscle activity at its lowest - basically paralysed

Question 7

How long is a sleep cycle?

Answer 7

1 to 1 and a half hours

Question 8

When do we dream?

Answer 8

Usually during REM sleep however, it is not exclusive to REM

Heart rate also increases during REM sleep.

Question 9

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.

Answer 9

Start of the night – more NREM sleep

End of the night – more REM sleep

Question 10

Describe how heart rate and respiratory rate change during sleep.

Answer 10

SLOW during NREM

FAST during REM sleep

Question 11

What controls consciousness?

Answer 11

Reticular activating system which is found in the brainstem

Question 12

What projections does RAS have?

Answer 12

Network of neurons located in the brainstem

anterior projections to the hypothalamus, direct to cortex, posterior to thalamus

Question 13

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

Answer 13

Or via indirect connections through the intralaminar nuclei of the thalamus

Question 14

In layman’s terms what does RAS do?

Answer 14

Turns the lights on

Enables consciousness to happen and controls it

Question 15

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?

Answer 15

Lateral Hypothalamus – excitatory, promotes wakefulness via orexin/hypocretin neurotransmitter

Ventrolateral Preoptic Nucleus (anterior hypothalamus) – promotes sleep

NOTE: they have an antagonistic relationship

Question 16

Describe the circadian synchronisation of the sleep-wake cycle.

Answer 16

The suprachiasmatic nucleus is responsible for synchronising the sleep-wake cycle with falling light level, pathway that produces melatonin (makes you sleepy) . Stimulates pineal gland to produce melatonin. (ALSO HYPOTHALAMUS)

It receives an input from the retina (not from the usual photogenic cells) and as light level falls the suprachiasmatic nucleus becomes more active

Question 17

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

Answer 17

Falling light level à increased activity of suprachiasmatic nucleus

This leads to activation of ventrolateral preoptic nucleus and inhibition of lateral hypothalamus so you become sleepier

Question 18

What are the effects of sleep deprivation?

Answer 18

Psychiatric and neuro - 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

Question 19

How is sleep regulated accurately?

Answer 19

After sleep loss - reduced latency of sleep onset

increased slow wave sleep (NREM)

Increase of deep sleep ( after selective REM deprivation )

Question 20

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

Answer 20

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 than in real life

Question 21

What was the perception of the function of sleep and how were these theories/thoughts disporved?

Answer 21

Restoration and recovery - more active individuals don’t sleep more

Energy conservation - 10% drop in BMR but lying still is just as effective

Predator avoidance - but why is sleep so complex

Specific brain function - memory and consolidation THOUGHT TO BE A REAL PURPOSE

Question 22

When are dreams easier to recall?

Answer 22

When they are in REM sleep but are not exclusive to REM

More emotional and sensationalised than real life.

Question 23

What are the functions of dream?

Answer 23

• Safety valve for antisocial emotions
• Disposal of unwanted memories
• Memory consolidation

Question 24

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

Answer 24

NREM – declarative = facts and events

REM – procedural = learning skills

Question 25

Describe the incidence of insomnia

Answer 25

• High prevalence
• Most cases transient

Question 26

What are some of the causes of chronic insomnia?

Answer 26

– physiological e.g. sleep apnea, chronic pain

– Brain dysfunction eg. depression, fatal familial insomnia, night working

Question 27

What are treatments for insomnia?

Answer 27

sleep hygiene : Establish fixed times for sleep and wake, relaxing bedtime routine, only go bed when you feel tired, comfortable sleeping environment, not napping, avoid caffeine, don’t eat heavy meal, not using lit back devices before bed.

– hypnotics (most enhance GABAergic circuits)

– sleep CBT (cognitive behaviour therapy)

Question 28

What is hypersomnia?

Answer 28

Excessive daytime sleepiness

secondary causes due to poor quality of overnight sleep - obstructive sleep apnoea, restless leg syndrome, nocturnal pain, neurodegenerative disease and some rarer causes being oseophageal acid reflux and severe bruxism

Question 29

Narcolepsy is a primary cause of hypersomnia, what is it and give some other primary causes

Answer 29

Narcolepsy is a condition characterised by an extreme tendency to fall asleep whenever in relaxing surroundings. Leads to falling asleep repeatedly during the day and disturbed sleep at night. Cataplexy, dysfunction of REM and orexin/hypocretin deficiency.

Other causes - idiopathic hypersomnolence and post traumatic brain injury

Question 30

What is Cataplexy?

Answer 30

Sudden brief loss of voluntary muscle tone which can be triggered by strong emotions such as laughter.

One of the manifestations of narcolepsy

Question 31

Explain narcolepsy with regards to the sleep cycle.

Answer 31

It tends to be due to a dysfunction of control of REM sleep

Patients go straight to REM sleep without going through NREM sleep so they become paralysed

Question 32

What are the potential consequences of working night shifts?

Answer 32

Physiological processes could become desynchronised

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