Which phase of sleep is characterized by no eye movement and minimal muscle activity?

The correct answer highlights the characteristics of NREM sleep, which stands for Non-Rapid Eye Movement sleep. This phase of sleep is categorized by the absence of rapid eye movement, which distinguishes it from REM sleep, where such eye activity is prominent. During NREM sleep, there is a noticeable reduction in muscle activity, contributing to a restful state of the body.

NREM sleep consists of several stages, including Stage 1 and Stage 2, both of which are characterized by varying degrees of light sleep, but they still fall under the broader category of NREM. While in Stage 1 sleep, individuals experience light sleep with some muscle activity, which can sometimes lead to muscle jerks. Stage 2 sleep is characterized by further relaxation and occasional bursts of brain activity (sleep spindles), but it still does not exhibit the eye movements found in REM sleep.

In summary, NREM sleep as a whole captures the essence of minimal muscle activity and the absence of eye movements, distinguished from its specific phases and REM sleep dynamics.