L19 - Sleep

Question 1

What is the function of sleep in biological rhythms?

Answer 1

Sleep is an active, brain-driven process regulated by the circadian rhythm, which operates in roughly 24-hour cycles.

Question 2

What are circadian rhythms?

Answer 2

Biological processes that follow a 24-hour cycle, including temperature, hormones, heart rate, and blood pressure.

Question 3

What is the “free-running” cycle?

Answer 3

An internal biological clock that persists without external cues, typically slightly longer than 24 hours in humans.

Question 4

What is entrainment in circadian rhythms?

Answer 4

The synchronization of internal biological clocks to external cues like light, food availability, and temperature.

Question 5

How does jetlag affect circadian rhythms?

Answer 5

Traveling east requires a phase advance, while traveling west requires a phase delay, causing misalignment between internal and external clocks

Question 6

Why is eastward travel harder than westward travel for most people?

Answer 6

The body’s internal clock naturally runs longer than 24 hours, making it easier to lengthen the day than shorten it.

Question 7

What are the effects of sleep deprivation?

Answer 7

Impaired cognitive abilities

reduced alertness

potential impacts on immune function, but no significant impact on physical exercise capacity.

Question 8

What is the adaptive hypothesis of sleep?

Answer 8

Sleep conserves energy and reduces risk of predation, with body size and vulnerability influencing sleep duration.

Question 9

What is the restorative hypothesis of sleep?

Answer 9

Sleep helps restore and repair the brain by reducing metabolic rates, clearing free radicals, and flushing out waste via cerebrospinal fluid.

Question 10

How does sleep impact memory consolidation?

Answer 10

Slow-wave sleep improves declarative memory, while REM sleep enhances non-declarative memory and motor skill learning.

Question 11

What evidence links sleep to memory consolidation?

Answer 11

Sleep strengthens hippocampal activity, and neural replay during sleep reflects prior learning experiences.

Question 12

What are the main arousal systems that regulate wakefulness?

Answer 12

Acetylcholine

norepinephrine

serotonin

histamine

orexin.

Question 13

What role does acetylcholine play in sleep and wakefulness?

Answer 13

It promotes cortical arousal and attention, with activity high during waking and low during deep sleep.

Question 14

How does norepinephrine regulate vigilance?

Answer 14

Originating in the locus coeruleus, its activity is high during wakefulness and decreases during deep sleep.

Question 15

What is the role of serotonin in the sleep-wake cycle?

Answer 15

Released from the raphe nuclei, serotonin promotes automatic movements and decreases during deep sleep.

Question 16

How does orexin stabilize sleep-wake states?

Answer 16

Orexin counteracts sleep pressure, helping maintain wakefulness and regulating the flip-flop mechanism.

Question 17

How is sleep studied using EEG?

Answer 17

EEG measures brain waves, showing low-amplitude, high-frequency activity during wakefulness and high-amplitude, low-frequency activity during deep sleep.

Question 18

What are the characteristics of REM sleep?

Answer 18

REM shows paradoxical awake-like EEG activity, vivid dreaming, and muscle paralysis to prevent acting out dreams.

Question 19

How does REM sleep change throughout the night?

Answer 19

REM periods become progressively longer with each sleep cycle.

Question 20

What is the role of the suprachiasmatic nucleus (SCN) in sleep?

Answer 20

The SCN acts as the internal circadian clock, regulating sleep-wake cycles based on environmental light cues.

Question 21

What happens when the SCN is lesioned?

Answer 21

The circadian pattern of sleep is disrupted, resulting in random sleep bouts, but the total amount of sleep remains unchanged.

Question 22

How is the SCN entrained to light cues?

Answer 22

Specialized retinal ganglion cells containing melanopsin project to the SCN via the retinohypothalamic pathway.

Question 23

What causes SCN intracellular ticking?

Answer 23

Negative feedback loops involving specific proteins regulate the internal circadian clock.

Question 24

What is narcolepsy?

Answer 24

A neurological sleep disorder characterized by sudden transitions into REM sleep, often involving cataplexy, sleep paralysis, and hypnagogic hallucinations.

Question 25

What causes narcolepsy?

Answer 25

Dysregulation of the orexin system, which destabilizes the sleep-wake flip-flop mechanism

Question 26

What is REM rebound?

Answer 26

Increased time spent in REM sleep after REM deprivation.

Question 27

Why do newborns spend more time in REM sleep?

Answer 27

REM sleep is critical for brain development, especially in species with immature brains at birth.

Question 28

Why is sleep essential for cognitive function?

Answer 28

It enhances memory consolidation, supports learning, and maintains neural plasticity.

Question 29

How does the brain coordinate sleep-wake cycles?

Answer 29

Through the interaction of arousal systems, SCN timing, and the flip-flop mechanism regulating transitions between sleep and wakefulness.

Question 30

What is the role of the retinohypothalamic pathway?

Answer 30

It links light cues to the SCN, synchronizing internal clocks with the external day-night cycle.