AP PSYCHOLOGY

Detailed explanation-1: -Stage 2 sleep is characterized by the appearance of both sleep spindles and K-complexes. Stage 3 and stage 4 of sleep are often referred to as deep sleep or slow-wave sleep because these stages are characterized by low frequency (up to 4 Hz), high amplitude delta waves (figuer below).

Detailed explanation-2: -Sleep spindles may be present in all stages of NREM, but they are most prevalent in stage 2 sleep.

Detailed explanation-3: -Stage 2: This period of light sleep features periods of muscle tone (muscles partially contracting) mixed with periods of muscle relaxation. Your eye movement stops, heart rate slows and body temperature decreases. Brain waves become slower.

Detailed explanation-4: -The fourth is rapid eye movement (REM) sleep, also known as active sleep. In stage 1, you transition from wakefulness to sleep. In stage 2 you enter light sleep. By stage 3 you are in a deep sleep.

Detailed explanation-5: -Sleep spindles, a defining characteristic of stage 2 sleep, are brief, powerful bursts of synchronous ∼12–15 Hz neuronal firing in thalamocortical networks that occur most frequently late in the night.