Sleep Functions, Stages, and Circadian Rhythms: Key Concepts for Psychology and Biology

What is one key function of sleep related to energy?

Sleep helps conserve energy by lowering metabolic rate and body temperature, allowing the brain to restore energy (ATP).

How does sleep support physical recovery?

It enables the body to repair tissues and heal damage.

What role does sleep play in brain maintenance?

Sleep clears waste products and consolidates memories.

What is NREM sleep?

Non-Rapid Eye Movement sleep, which includes light sleep and deeper stages.

What occurs during Stage 1 of NREM sleep?

Light sleep that occurs right after falling asleep, may experience hypnagogic hallucinations.

What characterizes Stage 2 of NREM sleep?

Deeper sleep where brain activity slows.

What is Stage 3 of NREM sleep known for?

Deep sleep with very slow brain waves.

What is REM sleep?

Rapid Eye Movement sleep where most dreaming occurs and brain activity resembles being awake.

How long do sleep cycles typically last?

About 90-120 minutes, with a full 8 hours including 4-5 cycles.

What is a circadian rhythm?

An internal 24-hour biological clock controlled by the suprachiasmatic nucleus (SCN).

How does light affect circadian rhythms?

Light is detected by retinal cells that send signals to the SCN, allowing the brain to interpret environmental light conditions.

What happens in the morning regarding SCN activity?

The SCN stimulates cortisol release, increases core body temperature, and overall metabolic activity.

What occurs in the evening as light decreases?

The SCN leads to the release of melatonin via the pineal gland and a decrease in body temperature and metabolic activity.

How does screen time affect sleep?

Screens emit blue light, which suppresses melatonin production and delays the body's sleep signal.

What is one effect of delayed sleep onset?

Falling asleep later due to disrupted sleep signals.

What is a consequence of reduced sleep duration?

Less total sleep leads to fewer sleep cycles completed.

What are cognitive consequences of poor sleep?

Reduced attention and impaired memory consolidation.

What mental health issues can arise from poor sleep?

Increased stress, anxiety, and risk of depression.

What physical effects can result from poor sleep?

Fatigue, weakened immune system, and metabolic disruption.