Sleep Structure and Homeostatic Sleep Drive

Flashcards for reviewing the structure of normal sleep, sleep stages and the homeostatic sleep drive.

Two Types of Sleep

Sleep is made up of two different types: non-rapid eye movement (non-REM) and rapid eye movement (REM) sleep.

Non-REM Sleep Characteristics

Breathing and heart rate slow down and become more regular; neuronal activity slows.

REM Sleep Characteristics

Rapid side-to-side eye movements; neuronal activity speeds up (sometimes more active than wakefulness); postural muscles are paralyzed.

REM Sleep Function

Associated with vivid dreams and muscle paralysis to prevent injury.

Non-REM Sleep Stages

N1, N2, and N3. N1 and N2 are light sleep; N3 is deep sleep.

Slow Wave Sleep

N3 sleep, characterized by slow waves of neuronal activity.

Hypnogram

A graph depicting different sleep stages across a night.

Sleep Entry

Adults typically enter sleep through N1, lasting 1-7 minutes before progressing to deeper stages.

Sleep Cycle

The transition from N1 to N2 to N3 to REM sleep; averages 90 minutes long.

Sleep Cycle Progression

REM periods become longer, dominating the last third of the night; N3 dominates the first third.

Arousals

Brief transitions from sleep to waking activity; average young adult experiences 10-15 per hour.

Normal Sleep Structure

Normal sleep is usually entered through non-REM sleep, with cycles averaging 90 minutes.

Sleep Stage Proportions

N1 (2-5%), N2 (45-55%), N3 (3-25%), REM (20-25%); non-REM typically makes up 75-80% of the sleep period.

Two Main Sleep Regulators

The homeostatic sleep drive and the circadian timekeeping system.

Homeostatic Sleep Drive

Represents our pressure or need for sleep; increases with time awake and diminishes with sleep.

Homeostatic Process

The process ensures we meet our daily sleep needs; brain promotes more sleep when we miss it or wakes us when we sleep too long.

Compensating for Missing Sleep

Sleep structure changes to have more slow waves during N3 sleep and longer periods of N3 sleep and the amount of sleep we need is increased.