During REM sleep, the ascending arousal system shows a specific pattern. Which neurotransmitter system becomes MOST active during REM sleep, driving the characteristic features?

• A Norepinephrine from locus coeruleus
• B Serotonin from raphe nuclei
• C Histamine from tuberomammillary nucleus
• D Acetylcholine from pedunculopontine and laterodorsal tegmental nuclei ✓

Explanation

REM sleep is generated and maintained primarily by cholinergic neurons in the pedunculopontine tegmentum (PPT) and laterodorsal tegmentum (LDT). These neurons fire maximally during REM sleep (REM-on neurons). In contrast, noradrenergic (locus coeruleus), serotonergic (raphe), and histaminergic (tuberomammillary) neurons are virtually silent during REM — they are Wake-on/REM-off cells. The cholinergic activation produces cortical desynchronization, rapid eye movements, and brainstem muscle atonia.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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