When you go to sleep, you begin with Stage 1, then Stage 2, then Stage 3, and then Stage 4. What is the next stage?

Stage 5 of the sleep cycle, or REM sleep, is the stage of sleep associated with dreaming. It is very different physiologically from the other stages of sleep. The EEG resembles wake time. However, the skeletal muscles are atonic, or without movement. The breathing is more erratic and irregular. The heart rate often increases. It is theorized that muscle atonia evolved in order to protect the individual from injury during sleep.

Explanation:

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