Use a consistent color palette across your slides (e.g., Light Blue for N1, Dark Blue for N2, Purple for N3, and Red for REM).
Stage N1 accounts for roughly 2% to 5% of total sleep time. It represents the fragile bridge between wakefulness and sleep.
: Associated with alert wakefulness and concentration.
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Measures muscle tone (typically placed on the chin). ECG/EKG: Monitors cardiac rhythm.
To initiate sleep, the wake-promoting circuits must be inhibited.
| Feature | NREM Sleep (Stages N1-N3) | REM Sleep (Paradoxical) | | :--- | :--- | :--- | | | Synchronized, high voltage, slow frequency (Theta/Delta) | Desynchronized, low voltage, mixed frequency (Beta) | | Muscle Tone | Decreased but present | Atonia (Paralysis) | | Eye Movements | Absent or slow rolling | Rapid, darting movements | | Autonomic NS | Stable, regular heart rate/BP | Variable, irregular, surges | | Dreaming | Simple, thought-like mentation | Vivid, narrative, bizarre | | Key Function | Body repair, waste clearance, energy restoration | Memory consolidation, brain development | Use a consistent color palette across your slides (e
Drowsy states, light sleep, and NREM Stage 1 and 2 sleep.
Sleep is not simply the absence of wakefulness. It is defined as a reversible, neurobehavioral state characterized by reduced awareness, altered metabolism, and distinct patterns of brain activity. Sleep is an active physiological process that is highly conserved across species, meaning it is fundamental to survival. On average, humans spend approximately 23 years of their lives asleep, but the quality and architecture of this sleep are far more critical than duration alone.
EEG rhythms are classified by their frequency (Hz) and amplitude. These different bands correlate with specific states of consciousness: : Associated with alert wakefulness and concentration
Stage N2 is the first true "sleep" signature and accounts for 45–55% of total sleep time in adults. The EEG is characterized by the presence of two specific transient events superimposed on a background of theta waves:
| Band | Frequency | Associated State | | :--- | :--- | :--- | | | 0.5–4 Hz | Deep, dreamless sleep (N3); slow-wave sleep | | Theta (θ) | 4–8 Hz | Light sleep, drowsiness, deep relaxation, memory encoding | | Alpha (α) | 8–13 Hz | Wakeful relaxation, eyes closed, calm with mental inactivity | | Beta (β) | 13–30 Hz | Active wakefulness, alert concentration, problem-solving | | Gamma (γ) | > 30 Hz | Higher cognitive processing, focused attention |
: The EOG channels show lazy, sinusoidal movements, differentiating N1 from active wakefulness. Slide 6: Non-REM Stage 2 (N2) – Standard Core Sleep