L19 - Sleep Flashcards
What is the function of sleep in biological rhythms?
Sleep is an active, brain-driven process regulated by the circadian rhythm, which operates in roughly 24-hour cycles.
What are circadian rhythms?
Biological processes that follow a 24-hour cycle, including temperature, hormones, heart rate, and blood pressure.
What is the “free-running” cycle?
An internal biological clock that persists without external cues, typically slightly longer than 24 hours in humans.
What is entrainment in circadian rhythms?
The synchronization of internal biological clocks to external cues like light, food availability, and temperature.
How does jetlag affect circadian rhythms?
Traveling east requires a phase advance, while traveling west requires a phase delay, causing misalignment between internal and external clocks
Why is eastward travel harder than westward travel for most people?
The body’s internal clock naturally runs longer than 24 hours, making it easier to lengthen the day than shorten it.
What are the effects of sleep deprivation?
Impaired cognitive abilities
reduced alertness
potential impacts on immune function, but no significant impact on physical exercise capacity.
What is the adaptive hypothesis of sleep?
Sleep conserves energy and reduces risk of predation, with body size and vulnerability influencing sleep duration.
What is the restorative hypothesis of sleep?
Sleep helps restore and repair the brain by reducing metabolic rates, clearing free radicals, and flushing out waste via cerebrospinal fluid.
How does sleep impact memory consolidation?
Slow-wave sleep improves declarative memory, while REM sleep enhances non-declarative memory and motor skill learning.
What evidence links sleep to memory consolidation?
Sleep strengthens hippocampal activity, and neural replay during sleep reflects prior learning experiences.
What are the main arousal systems that regulate wakefulness?
Acetylcholine
norepinephrine
serotonin
histamine
orexin.
What role does acetylcholine play in sleep and wakefulness?
It promotes cortical arousal and attention, with activity high during waking and low during deep sleep.
How does norepinephrine regulate vigilance?
Originating in the locus coeruleus, its activity is high during wakefulness and decreases during deep sleep.
What is the role of serotonin in the sleep-wake cycle?
Released from the raphe nuclei, serotonin promotes automatic movements and decreases during deep sleep.
How does orexin stabilize sleep-wake states?
Orexin counteracts sleep pressure, helping maintain wakefulness and regulating the flip-flop mechanism.
How is sleep studied using EEG?
EEG measures brain waves, showing low-amplitude, high-frequency activity during wakefulness and high-amplitude, low-frequency activity during deep sleep.
What are the characteristics of REM sleep?
REM shows paradoxical awake-like EEG activity, vivid dreaming, and muscle paralysis to prevent acting out dreams.
How does REM sleep change throughout the night?
REM periods become progressively longer with each sleep cycle.
What is the role of the suprachiasmatic nucleus (SCN) in sleep?
The SCN acts as the internal circadian clock, regulating sleep-wake cycles based on environmental light cues.
What happens when the SCN is lesioned?
The circadian pattern of sleep is disrupted, resulting in random sleep bouts, but the total amount of sleep remains unchanged.
How is the SCN entrained to light cues?
Specialized retinal ganglion cells containing melanopsin project to the SCN via the retinohypothalamic pathway.
What causes SCN intracellular ticking?
Negative feedback loops involving specific proteins regulate the internal circadian clock.
What is narcolepsy?
A neurological sleep disorder characterized by sudden transitions into REM sleep, often involving cataplexy, sleep paralysis, and hypnagogic hallucinations.
What causes narcolepsy?
Dysregulation of the orexin system, which destabilizes the sleep-wake flip-flop mechanism
What is REM rebound?
Increased time spent in REM sleep after REM deprivation.
Why do newborns spend more time in REM sleep?
REM sleep is critical for brain development, especially in species with immature brains at birth.
Why is sleep essential for cognitive function?
It enhances memory consolidation, supports learning, and maintains neural plasticity.
How does the brain coordinate sleep-wake cycles?
Through the interaction of arousal systems, SCN timing, and the flip-flop mechanism regulating transitions between sleep and wakefulness.
What is the role of the retinohypothalamic pathway?
It links light cues to the SCN, synchronizing internal clocks with the external day-night cycle.
