Which statement describes the initial night stage with low-amplitude brain waves and reduced muscle tension?

Which statement describes the initial night stage with low-amplitude brain waves and reduced muscle tension?

• A. NREM stage 2
• B. NREM stage 1
• C. REM sleep
• D. Paradoxical sleep

Answer: (B)

Understanding sleep stages helps you see why this is the first night stage. When you first fall asleep, the brain shifts from wakeful activity to lighter NREM sleep. The EEG shows theta waves—lower frequency and relatively low amplitude—reflecting a relaxed, drifting brain. At the same time, muscle tone is reduced compared with being awake, and you may experience brief hypnic jerks as you settle in. This combination of low-amplitude, slower brain waves and diminished muscle activity points to NREM stage 1, the initial stage of sleep. REM sleep, also called paradoxical sleep, features rapid eye movements and near-complete muscle paralysis, with brain activity that can resemble wakefulness. It isn’t the first stage of the night. NREM stage 2, on the other hand, brings distinctive features like sleep spindles and K-complexes, not present in the initial stage. So the initial night stage with low-amplitude brain waves and reduced muscle tension is NREM stage 1.

Understanding sleep stages helps you see why this is the first night stage. When you first fall asleep, the brain shifts from wakeful activity to lighter NREM sleep. The EEG shows theta waves—lower frequency and relatively low amplitude—reflecting a relaxed, drifting brain. At the same time, muscle tone is reduced compared with being awake, and you may experience brief hypnic jerks as you settle in. This combination of low-amplitude, slower brain waves and diminished muscle activity points to NREM stage 1, the initial stage of sleep.

REM sleep, also called paradoxical sleep, features rapid eye movements and near-complete muscle paralysis, with brain activity that can resemble wakefulness. It isn’t the first stage of the night. NREM stage 2, on the other hand, brings distinctive features like sleep spindles and K-complexes, not present in the initial stage. So the initial night stage with low-amplitude brain waves and reduced muscle tension is NREM stage 1.