During rem sleep, your skeletal muscles are relaxed because messages from the motor cortex are blocked by the

Brainstem

Explanation:

During REM sleep , the electrical activity of our muscles get reduced or paralysed which is primarly due to blocking of messages by the brainstem.

Trigeminal motor neurons found in the brain cell helps in moving the muscles but during REM sleep, the two neurotransmitter receptors namely GABAA and glycine are paralysed by the brain stem and hence no muscle activity could be observed during the REM sleep

when it is at an intermediate population density