Muscle tone is absent during which sleep stage?

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Multiple Choice

Muscle tone is absent during which sleep stage?

During REM sleep, the brainstem activates inhibitory pathways that suppress motor neuron activity in the spinal cord, producing REM atonia. This results in almost no skeletal muscle tone, which is why you typically don’t move while dreaming. Only the eyes and the diaphragm remain relatively active, allowing breathing and rapid eye movements. In contrast, wakefulness and the non‑REM stages maintain normal or near-normal muscle tone, with only brief, subtle variations. This is why muscle tone is absent specifically in REM sleep. Clinically, disruption of REM atonia can lead to REM sleep behavior disorder, where dream content may be enacted.

During REM sleep, the brainstem activates inhibitory pathways that suppress motor neuron activity in the spinal cord, producing REM atonia. This results in almost no skeletal muscle tone, which is why you typically don’t move while dreaming. Only the eyes and the diaphragm remain relatively active, allowing breathing and rapid eye movements. In contrast, wakefulness and the non‑REM stages maintain normal or near-normal muscle tone, with only brief, subtle variations. This is why muscle tone is absent specifically in REM sleep. Clinically, disruption of REM atonia can lead to REM sleep behavior disorder, where dream content may be enacted.

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