LECTURE 19 – SLEEP & DREAMS

This set of flashcards covers key concepts and details from the lecture on sleep and dreams, including circadian rhythms, melatonin, sleep stages, and more.

What is a circadian rhythm?

A ~24-hour biological cycle that regulates physiological processes.

What is the master circadian pacemaker?

The suprachiasmatic nucleus (SCN) in the hypothalamus.

What external cue primarily resets the circadian rhythm?

Light.

Which cells detect light and send signals to the SCN?

Retinal ganglion cells.

What pigment do these retinal cells contain?

Melanopsin.

What does the pineal gland produce?

Melatonin.

When does melatonin rise?

In darkness (1–3 hours after dark).

When is melatonin suppressed?

With light exposure.

What does melatonin regulate?

Sleep timing and circadian rhythm alignment.

How does darkness activate melatonin release?

Retinal signal → SCN → secondary pathway → pineal gland.

What is melatonin’s effect?

Promotes sleepiness and circadian alignment.

What cognitive functions does sleep support?

Memory consolidation and learning.

What physiological processes depend on sleep?

Physical restoration, immune support, metabolic regulation.

What emotional function does sleep regulate?

Mood and emotional stability.

What are the two major types of sleep?

NREM (Stages 1–3) and REM sleep.

Which type has the most restorative functions?

NREM, especially Stage 3 (deep sleep).

What occurs in N1?

Light transitional sleep.

What EEG pattern is seen in N1?

Theta waves.

What percent of total sleep is N2?

~50%.

What EEG features define N2?

Sleep spindles and K-complexes.

What waves are dominant in N3?

Delta waves.

What is N3 associated with?

Tissue repair, immune function, memory consolidation, physical restoration.

What happens to brain activity during REM?

It resembles wakefulness.

What occurs during REM sleep?

Dreaming, emotional processing, memory consolidation.

What happens to voluntary muscles during REM?

Muscle atonia (paralysis).

Why does muscle atonia occur?

To prevent acting out dreams.

Do we cycle between NREM and REM?

Yes, in ~90-minute cycles.

Which stage increases as the night progresses?

REM sleep.

Which stage decreases across the night?

Deep sleep (N3).

What is considered high-quality sleep?

Staying asleep through the night with proper cycling.

How much sleep do adults need?

~7–9 hours per night.

What is sleep apnea?

Repeated pauses in breathing during sleep.

What causes obstructive sleep apnea?

Blockage of the airway during sleep.

What are risk factors for sleep apnea?

Age, obesity, smoking, diabetes, cardiovascular disease.

What does sleep apnea disrupt?

Sleep architecture and oxygen levels.

What cognitive impairments occur with poor sleep?

Attention deficits, memory problems, impaired decision-making.

What emotional issues occur with sleep deprivation?

Irritability, depression worsening.

What physical consequences occur due to sleep deprivation?

Immune dysfunction, metabolic issues, increased disease risk.

Who is at highest risk for circadian disruption?

Night shift workers.

What does WHO classify shift work as?

A probable carcinogen.

What diseases have higher rates in shift workers?

Breast cancer, cardiovascular mortality.

Why does shift work increase disease risk?

Chronic circadian misalignment.

What should be avoided before bedtime?

Caffeine, nicotine, alcohol.

What environment promotes good sleep?

Dark room, cool temperature, quiet environment.

What is recommended if you can’t fall asleep?

Get out of bed and return only when sleepy.

What is the rule for bedroom use?

Use bed ONLY for sleep (not studying, TV, etc.).

What should you minimize at night?

Light exposure, especially blue light.

When do most dreams occur?

During REM sleep.

What functions are dreams thought to support?

Emotional processing, memory organization, creative problem-solving.

Define circadian misalignment.

Mismatch between internal clock and external schedule.

Define melatonin.

Hormone that signals darkness & promotes sleep.

Define atonia.

REM-induced muscle paralysis.