2022 Regulation of alertness sleepiness Tight regulation Homeostatic the more we stay awake the more sleep pressure we build Circadian endogenous 24hour rhythm controlled by the suprachiasmatic ID: 1043585
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1. Slides for Wits integrates Experience 2022
2. Regulation of alertness/ sleepinessTight regulation Homeostatic: the more we stay awake, the more sleep pressure we build.Circadian: endogenous 24-hour rhythm controlled by the suprachiasmatic nucleus of the hypothalamus. Modulates sleep & wake signals
3. Circadian pacemaker: suprachiasmatic nucleus of the hypothalamus
4. Circadian controlAdapted from Borbely et al -19828162481624Time of dayWakefulness signalProcess C= circadian processMelatonin
5. Time of dayHomeostatic controlAdapted from Borbely et al -19820510152025303540Sleep pressureElapsed time awakeProcess S= homeostatic processAdenosine
6. 0510152025303540Sleep pressureElapsed time awake8162481624Normal alignment with an 8h sleep episode within each 24-h dayTime of dayWakefulness signalNormal alignment but one night of sleep deprivationCircadian and homeostatic controlAdapted from Borbely et al -1982
7. AdenosineMelatonin
8. Measurements of drowsiness Karolinska Sleepiness Scale 1 extremely alert 2 very alert 3 alert 4 rather alert 5 neither alert nor sleepy 6 some signs of sleepiness 7 sleepy, no effort to stay awake 8 sleepy some effort to stay awake 9 very sleepy, great effort to stay awake, fighting sleepReaction timesNormally ~ 200 msLapse: when it takes >500 msecs to react to a stimulus
9. Effect of increased wakefulness/ sleep deprivation on performance & sleepinessDiamond-shaped: 8h sleep (14 days)Open squares: 6h sleep (14 days)Circles: 4h sleep (14 days)Full squares: 0h (3 days)Lapses: >500ms to reactto the testVan Dongen et al, Sleep, 2003
10. Vehicle accidents caused by drowsy driving exceed those caused by alcohol & drugs combined!!** USA: 1.2 million accidents = caused by sleepiness each yeari.e. every 30 seconds there’s a car accident caused by sleepiness somewhere in the USA
11. Broader effects of Sleep deprivationCVS effects – stroke, congestive heart failure, hypertension …Metabolic effects – blood glucose levels … Hormone effects – appetite - ↑ BMI …Immune system effects – cancer …Psychiatric effects – depression, anxiety, suicidalityCognitive effects – Alzheimer’s, bipolar disease…PLUS ??THE SHORTER ONE SLEEPS, THE SHORTER ONE’S LIFESPAN!!
12. Subjective sense of impairment with sleep lossMultiple experiments by David Dinges, also by G.BelenkyTen days of 6 hr sleep = SD for 24h straight! No sign of levelling out! i.e performance would continue to deteriorate with continued sleep lossNo help from “sleeping it off!”Subjective sense of impairment?Consistently underestimated how bad their performance wasYOU DO NOT KNOW HOW SLEEP-DEPRIVED YOU ARE WHEN YOU ARE SLEEP-DEPRIVED!
13. How did the Pilot stay awake?
14. How did the Pilot stay awake?