sleep Flashcards
definitions of sleep
- the natural periodic suspension of consciousness during which the powers of the body are restored
- the intermediate state between wakefulness and death
- a reversible behavioral state of perceptual disengagement from and unresponsiveness to the environment
average hours needed for sleep
7-9 hours
REM:NREM ratios
newborn
infant
adult
newborn
- REM:NREM 50:50
- Enter sleep through SOREM (Sleep Onset REM Periods)
Infant-child
- ~REM:NREM ~50:~50
- as children age, they experience more NREM
- By 3 months, children enter sleep via NREM
Adult
- NREM:REM ~75:~25
- REM cycles every 90-120 minutes
NREM vs. NREM
NREM sleep predominates in first half of sleep and is linked to prior level of wavefulness
REM predominates in last half of sleep and is circadian linked
Homeostatic Sleep Drive model
Sleep responses are proportional to the duration of prior wakefullnes
- Increased sleepiness
- Increased sleep
- Increased depth and maintenance of sleep
Circadian Rhythm model
circadian rythm model
- Rythem generated by circadian pacemaker located in the suprachismaltic nuclei of the hypothalamus
- common to the specific organism (each organism has its own sleep cycle i.e nochturnal)
- Rythem is set by photic and Non-photic stimuli
retinal blindness blocks light that drives biological clock no circadian rythem
Systems controlled by the circadian rythem
[*] Airway function
[*] Cardiovascular activity
[*] Hematology
[*] Neoplastic cells
[*] Wake/sleep
[*] Hormonal
[*] Temperature
[*] Immune
[*] Drug metabolism
[*] Renal function
Determiniants of sleep
- Circadian
- Homeostatic
- Age
- Others
- drugs
- sleep disorders
- Total sleep requirement and the timing of the wake/sleep cycle are inherent characteristics of an individual
Sleep deprevation epidemic
- As a society, we now get 20% less sleep than our ancestors only 100 years ago.
- College students oversleep their alarms 50% of the time.
Sleep Debt stats
Sleep deprivation is cumulative.
- A person does not come to require less sleep or get used to being sleep-deprived.
- sleep deprevation creates sleep debt that must be resotred inorder to feel refreshed
- The payback requirement is less than the debt at a ratio of about 2.5h of debt to 1h sleep.
Social cost of sleep debt
- Major industrial disasters e.g. Chernobyl, Three Mile Island, and Bhopal, and serious accidents, e.g Exxon Valdez and Challenger, have been officially attributed to errors in judgment caused by lack of sleep.
- Car crashes, in the US, due to falling asleep at the wheel exceed 100,000/year and result in 1,500 deaths
Polysomnography: Scoring and Staging
Polysomnography: Scoring and Staging
- overnight sleep study
- measures: EEG, EOG, EMG, Leg EMG, Airflow, Respiratory Effort, ECG
Stages of sleep
Stage W (Wakefulness)
NREM
- Stage N1 (NREM 1)
- Stage N2 (NREM 2)
- Stage N3 (NREM 3)
Stage R (REM)
Multiple Sleep Latency Test
Five 20-minute nap opportunities are given at two-hour intervals.
Parameters measured are:
- average latency to sleep onset
- appearance of REM sleep
Norms for sleep latency(time to fall asleep):
- 0-5 minutes indicative of severe hypersomnia
- <5 and >10 borderline
- 10 to 20 normal
- 2 or more naps with REM periods: abnormal
- indicates narcolepsy
- 2 or more naps with REM periods: abnormal
Maintenance of Wakefulness Test
- Designed to test the patent’s ability to stay awake
- The patient is seated upright in bed in a dimly lighted room and asked to stay awake for 40 minutes
- Test is repeated 4 times throughout the day
