59 Sleep and consciousness

Question 1

We can measure sleep by:

1. EEG
2. EMG
3. EOG
4. ECG
5. Respiration

Answer 1

All of the above;

polysomnography

Question 2

In vegetative state, wakefulness is ______ and the level of awareness is _______.

Answer 2

High;

low

Question 3

What are the stages of sleep?

Answer 3

Wake > drowsiness (5-10%)
Stage 1-2: Light sleep (50%)
Stage 3: Slow wave sleep, deep sleep
Stage 4: REM sleep

Stages 1-3 = non-REM sleep

Question 4

In which stage of sleep does we have lowest awareness and arousal?

Answer 4

Deep sleep (stage 3 SWS)

Question 5

In which stage of sleep is where most dreams occur, and therefore a higher level of awareness?

Answer 5

REM sleep (stage 4)

Question 6

What is the feature of the EEG in REM sleep? What will happen to muscle tone?
Disorder?

Answer 6

• Saw tooth EEG
• rapid eye movement
• loss of muscle tone (except middle ear, eye, diaphragm)

REM disorder: preserved muscle tone > sleep walking

Question 7

Briefly compare and contrast NREM sleep and REM sleep.

Answer 7

1. Eye movement
   NREM: slow
   REM: rapid
2. Muscle tone
   NREM: preserved
   REM: atonia
3. Autonomic activities
   NREM: decreases
   REM: increases/variable
4. Dream
   NREM: thought-like process
   REM: colourful and emotional

Question 8

Removal of neurotoxic waste from brain is one of the important functions of sleep. How is it done?

Answer 8

Glymphatics, increases by 60% in interstitial space during sleep;
increase in exchange with CSF and interstitial fluid to increase neurotoxic waste (beta amyloid)

Question 9

What is synaptic homeostasis hypothesis?

Answer 9

There is synaptic downscaling during sleep, allowing the reuse of synapses for future encoding

Question 10

Circadian clock: transcriptional-translational feedback network.

Answer 10

BMAL and CLOCK gene form dimer in nucleus > Cry1 and Per1 > Leave nucleus to form dimer at cytoplasm > go back

Question 11

State the pathway for adjusting the circadian rhythm?

Answer 11

1. Light detected by retinal ganglion cells
2. release photopigment melanopsin
3. Afferents sent via retinohypothalamic tract
4. Project to suprachiasmatic nucleus that serves as a pacemaker, central master clock

Question 12

____________ send information to the hypothalamic nucleus/ pineal gland to suppress the production of melatonin in pineal gland > arousal.

Answer 12

Suprachiasmatic nucleus

Question 13

What is the function of melatonin?

Answer 13

Trigger sleepiness:

DLMO Dim light melatonin onset

Question 14

Other than melatonin, what are other biomarkers of sleep?

Answer 14

1. Core body temperature: lowest 2 hours before awake
2. Cortisol
3. Testosterone peak in early morning

Question 15

List all the wake neurotransmitters.

Answer 15

1. Norepinephrine
2. Serotonin
3. Acetylcholine
4. Histamine
5. Dopamine
6. Hypocretin

Question 16

List all the sleep neurotransmitters

Answer 16

1, Adenosine

2. GABA
3. Melatonin
4. IL-1
5. Galanin

Question 17

Why we can know histamine is a wake neurotransmitter?

Answer 17

When antihistamines are given (H1 receptor antagonists, e.g. chlorpheniramine), drowsiness can occur

Question 18

__________ antagonists greatly reduces cortical activation and thus causes drowsiness.

Answer 18

Serotonin

also SSRI, SNRI

Question 19

_____________ is released in high levels as a result of wakefulness and alertness. But it is also found in high levels during REM sleep, mainly released by the parabrachial area (reticular formation).

Answer 19

Acetylcholine

Question 20

Amphetamine increases __________ and therefore increase ____________________ (can treat ADHD, nacrolepsy)

Answer 20

dopamine secretion;

wakefulness, attention

Question 21

___________ is produced by the lateral nucleus of hypothalamus when awake.

Answer 21

Hypocretin/ Orexin

Question 22

Deficiency of hypocretin results in ________.

Answer 22

State instability known as narcolepsy 渴睡症 (flip flop switch: help avoid transitional states and abrupt sleep wake transitions)

Question 23

Benzodiazepines act by increasing __________(NT) to cause hypnosis.

Answer 23

GABA

Question 24

_______ induce sleep (in fever), significance: sleep may function to recover the immune system/ sleep deprivation may lead to impairment of the immune system.

Answer 24

IL-1 (interleukins)

Question 25

____________ acts as an inhibitor NT that suppresses the central nervous system, it is related to caffeine in which caffeine cross the BBB and is a competitive inhibitor of ___________ receptors.

Answer 25

Adenosine

Question 26

How can caffeine cause wakefulness?

Answer 26

It is structurally similar to adenosine and it as a competitive inhibitor of adenosine receptors

• removal of inhibitory effect of adenosine
• increase activity of adenylate cyclase AC, increase cAMP production, excitatory effects similar to norepinephrine and dopamine

Question 27

Function of melatonin?

Answer 27

DLMO
dim light melatonin onset
secretion is light-dependent

Question 28

Sleep deprivation may cause?
A. Hypotension
B. Worsen neurocognitive function 
C. Obesity 
D. Hyperglycemia

Answer 28

Except A

Hypertension

Question 29

When does parasomnia (sleepwalking) occur?

Features?

Answer 29

NREM Slow wave sleep (stage 3)

• amnesia, forgot about event
• difficult to be aroused
• DQBI gene
• dissociation of arousal and awareness

Question 30

In parasomnia (sleepwalking), which parts of the brain increases in cerebral blood flow?

Answer 30

• anterior cerebellum
• posterior cingulate cortex: autonomic and emotional responses
  (motor cortex > motor responses)

Question 31

Why there is a lack of insight and recall in parasomnia?

Answer 31

Deactivation of large areas of the frontal and parietal associative cortices