59 Sleep and consciousness Flashcards
We can measure sleep by:
- EEG
- EMG
- EOG
- ECG
- Respiration
All of the above;
polysomnography
In vegetative state, wakefulness is ______ and the level of awareness is _______.
High;
low
What are the stages of sleep?
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
In which stage of sleep does we have lowest awareness and arousal?
Deep sleep (stage 3 SWS)
In which stage of sleep is where most dreams occur, and therefore a higher level of awareness?
REM sleep (stage 4)
What is the feature of the EEG in REM sleep? What will happen to muscle tone?
Disorder?
- Saw tooth EEG
- rapid eye movement
- loss of muscle tone (except middle ear, eye, diaphragm)
REM disorder: preserved muscle tone > sleep walking
Briefly compare and contrast NREM sleep and REM sleep.
- Eye movement
NREM: slow
REM: rapid - Muscle tone
NREM: preserved
REM: atonia - Autonomic activities
NREM: decreases
REM: increases/variable - Dream
NREM: thought-like process
REM: colourful and emotional
Removal of neurotoxic waste from brain is one of the important functions of sleep. How is it done?
Glymphatics, increases by 60% in interstitial space during sleep;
increase in exchange with CSF and interstitial fluid to increase neurotoxic waste (beta amyloid)
What is synaptic homeostasis hypothesis?
There is synaptic downscaling during sleep, allowing the reuse of synapses for future encoding
Circadian clock: transcriptional-translational feedback network.
BMAL and CLOCK gene form dimer in nucleus > Cry1 and Per1 > Leave nucleus to form dimer at cytoplasm > go back
State the pathway for adjusting the circadian rhythm?
- Light detected by retinal ganglion cells
- release photopigment melanopsin
- Afferents sent via retinohypothalamic tract
- Project to suprachiasmatic nucleus that serves as a pacemaker, central master clock
____________ send information to the hypothalamic nucleus/ pineal gland to suppress the production of melatonin in pineal gland > arousal.
Suprachiasmatic nucleus
What is the function of melatonin?
Trigger sleepiness:
DLMO Dim light melatonin onset
Other than melatonin, what are other biomarkers of sleep?
- Core body temperature: lowest 2 hours before awake
- Cortisol
- Testosterone peak in early morning
List all the wake neurotransmitters.
- Norepinephrine
- Serotonin
- Acetylcholine
- Histamine
- Dopamine
- Hypocretin
List all the sleep neurotransmitters
1, Adenosine
- GABA
- Melatonin
- IL-1
- Galanin
Why we can know histamine is a wake neurotransmitter?
When antihistamines are given (H1 receptor antagonists, e.g. chlorpheniramine), drowsiness can occur
__________ antagonists greatly reduces cortical activation and thus causes drowsiness.
Serotonin
also SSRI, SNRI
_____________ 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).
Acetylcholine
Amphetamine increases __________ and therefore increase ____________________ (can treat ADHD, nacrolepsy)
dopamine secretion;
wakefulness, attention
___________ is produced by the lateral nucleus of hypothalamus when awake.
Hypocretin/ Orexin
Deficiency of hypocretin results in ________.
State instability known as narcolepsy 渴睡症 (flip flop switch: help avoid transitional states and abrupt sleep wake transitions)
Benzodiazepines act by increasing __________(NT) to cause hypnosis.
GABA
_______ induce sleep (in fever), significance: sleep may function to recover the immune system/ sleep deprivation may lead to impairment of the immune system.
IL-1 (interleukins)
____________ 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.
Adenosine
How can caffeine cause wakefulness?
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
Function of melatonin?
DLMO
dim light melatonin onset
secretion is light-dependent
Sleep deprivation may cause? A. Hypotension B. Worsen neurocognitive function C. Obesity D. Hyperglycemia
Except A
Hypertension
When does parasomnia (sleepwalking) occur?
Features?
NREM Slow wave sleep (stage 3)
- amnesia, forgot about event
- difficult to be aroused
- DQBI gene
- dissociation of arousal and awareness
In parasomnia (sleepwalking), which parts of the brain increases in cerebral blood flow?
- anterior cerebellum
- posterior cingulate cortex: autonomic and emotional responses
(motor cortex > motor responses)
Why there is a lack of insight and recall in parasomnia?
Deactivation of large areas of the frontal and parietal associative cortices
