Final answer:
Skeletal muscle tone is absent during REM sleep, which prevents individuals from acting out their dreams.
Step-by-step explanation:
The student asked if skeletal muscle tone is preserved or absent during REM sleep. During the REM (Rapid Eye Movement) phase of sleep, there is a marked absence of muscle tone in the skeletal muscles, a state known as REM atonia. This lack of muscle tone is what prevents individuals from acting out their dreams. REM sleep is often referred to as paradoxical sleep due to the combination of an active brain and a body that is effectively paralyzed. This paralysis of muscle systems, with the exception of those necessary for circulation and respiration, ensures that no voluntary movements occur.
However, there is a condition known as REM Sleep Behavior Disorder (RBD) where the usual muscle paralysis associated with REM sleep does not occur, leading to physical activity during REM sleep, such as kicking or punching. This disorder results in sleep disruptions and potential harm to individuals or their sleeping partners.