Sleep Flashcards
What is sleep?
Normal, recurring, reversible state in which there is an inability to respond to the external environment.
What is unconsciousness?
Lack of full awareness of self and environment.
What is consciousness?
Awareness of self and environment, and the ability to respond when stimulated.
What is REM sleep?
Rapid eye movement.
When does most NREM sleep occur?
At the start of the night.
What percentage of sleep for young adults is NREM?
Around 3/4.
Describe non rapid eye movement sleep.
- Synchronised rhythmic electroencephalography (EEG) activity, partial muscle relaxation and reduced cerebral blood flow.
- Reduced heart rate, blood pressure and tidal volumes.
- Some non-narrative images.
Describe REM sleep.
- Occurs mostly at the end of the night.
- EEG shows fast activity, fMRI (functional MRI) shows increased brain activity - similar to wakefulness.
- Atonic muscles with the exception of diaphragm and extraocular muscles.
- Increased cerebral blood flow and impaired thermal regulation.
- Narrative dreaming.
Why is deep sleep essential?
To allow cortex recovery after busy day.
What is the function of REM sleep?
- Mainly for early brain development.
- Likely dispensible.
- Seen as “non-wakefulness, not sleep”.
Which common drugs suppress REM sleep with no effect?
Tricyclics.
Neonates spend 16 hours a day asleep, what percentage of this is REM sleep?
50%.
Describe sleeping pattern of the elderly.
Increased awakenings, reduced REM latency and total sleep time and daytime napping.
What controls sleep?
- Biology and physiology.
NOT psychology. - Circadian rhythm is important for sleep-wake, appetite and hormone secretion.
Function of REM sleep?
- Consolidates memory and possibly deletes unnecessary memory files.
- Maintains immunocompetence.
What are circadian rhythms?
Endogenously controlled human processes.
e.g. sleep-wake, appetite, body temperature and hormone secretion, alertness.
Normal circadian rhythm lasts how long?
24 hours and 20 mins.
What entrains the body clock?
- Light. Uses retinal ganglion cells projecting to suprachiasmatic nucleus.
- Non-rod, non-cone cells.
There is no clinical evidence to suggest that muscle recovery occurs during sleep, but what does sleep help to repair?
Tissue repair.
What peaks during sleep?
- Cell division.
- Skin mitosis.
Most effects of lack sleep affect which part of the cortex?
Prefrontal - impaired alertness.
However, old and well rehearsed tasks, routine behaviour and logic tasks remain unaffected.
Effects of lack of sleep?
- Irritable, suspicious.
- Visual illusions.
- Microsleeps and concentration lapses.
What percentage of RTAs attended by police are sleep related?
= 10%.
Most are acute deprivation.
Double on non-urban roads.
Most likely cause of accidental death at work?
Truck driver falling asleep at wheel.
Total loss of truck and load £1.2million.
Most studies suggest what length of sleep is acceptable?
7 - 7.5 hours.
A mid afternoon nap of 15 minutes is equivalent to how many minutes of sleep overnight?
90 minutes.
What are parasomnias?
Abnormal events occurring during sleep.
Non-REM parasomnias occur from non-REM sleep, usually when?
During deep sleep - stage N3.
What is the most common type of parasomnia?
Non-REM, occurring in up to 20-30% of children.
Give some examples of non-REM parasomnias.
- Non-dreaming.
- Confusion arousals.
- Sleep walking.
- Sleep terrors and paralysis.
- Bruxism (grinding teeth).
- Restless legs and periodic limb movement of sleep (PLMS).
These are often complex behaviours.
Describe REM parasomnias.
- Often seen preceding parkinson’s.
- Dreaming.
- Much simpler behaviour then NREM parasomnias.
- Usually in the latter third of the night.
What is narcolepsy?
Rare long-term brain disorder causing someone to suddenly fall asleep at inappropriate times.
Sleep disorder characterised by excessive sleepiness, sleep paralysis, hallucinations.
Sometimes episodes of cataplexy (partial or total loss of muscle control, often triggered by strong emotion e.g. laughter).
Peak ages of narcolepsy onset?
15 and 36.
Clinical presentation of narcolepsy?
- Daytime sleepiness.
- Cataplexy.
- Hypnagogic hallucinations.
- Sleep paralysis.
- RBD: rem sleep behaviour disorder.
What are the features of daytime sleepiness that suggest a diagnosis of narcolepsy?
- Involuntary somnolence during eating/talking.
- Possibly severe and impossible to resist.
What is cataplexy?
- “To strike down with fear”.
- Present in 70% of those with narcolepsy.
- Loss of muscle tone often triggered by strong emotion e.g. laughing.
What are hypnagogic hallucinations?
Hallucinations which occur at sleep onset.
What is sleep paralysis?
Unable to move upon falling asleep or awakening with retained consciousness.
What percent of patients with REM sleep behaviour disorder (RBD) have narcolepsy?
Anywhere between 7-36%.
What is the delay between narcolepsy onset and diagnosis?
10 years.
50% of adults report symptom onset as teenagers.
What is the impact of narcolepsy?
- Impaired social and academic performance.
- Impaired job performance (sleep attacks, memory problems).
- Increased risk of death in automobile accidents.
Investigation of narcolepsy?
- Overnight polysomnography.
- Multiple sleep latency test.
- Lumbar puncture.
What is a multiple sleep latency test?
- 4 x 25 minute naps scheduled 2 hours apart.
- EEG, muscle activity and eye movement are recorded.
- Measures time from start of daytime nap to the first signs of sleep (sleep latency).
- Patients fall asleep faster if they are sleepier.
What is checked in a lumbar puncture in narcolepsy?
CSF hypocretin levels.
What CSF hypocretin levels of a lumbar puncture are consistent with narcolepsy?
Low i.e. <110pg/ml or 1/3 of the mean control value.
What advice should be given to someone with narcolepsy with regards to driving?
Cease driving on diagnosis until control is achieved.
Permanently excluded from driving Group 2 (lorries and buses).
