AN OVERVIEW OF THE PHYSIOLOGY OF SLEEP: NEURAL CIRCUITS AND REGULATORY MECHANISMS

Background: Sleep is a fundamental physiological process that supports neural restoration, cognitive functioning, and metabolic regulation. Understanding its neural control mechanisms is crucial for both basic science and clinical medicine. Sleep is a complex physiological state critical for the maintenance of physical and mental health. It facilitates cellular repair,cognitive processing, memory consolidation,and emotional regulation.The sleep wake cycle is orchestrated by an intricate network of neural circuits and neurotransmitters that coordinate circadian and homeostatic processes. This review outlines the essential neuroanatomy of sleep regulation, including the hypothalamus, brainstem, and thalamus, with emphasis on the roles of the ventrolateral preoptic nucleus (VLPO), suprachiasmatic nucleus (SCN), and the reticular activating system. It further explores the stages of non-REM and REM sleep, the neurotransmitters involved, and regulatory influences like adenosine and melatonin. Understanding sleep physiology is essential for diagnosing and treating disorders such as insomnia, narcolepsy, and sleep apnea. Objective: This review aims to outline the physiology of sleep, focusing on the neuroanatomical regions and neurotransmitters involved in the sleep-wake cycle. Content: The hypothalamus (especially the anterior hypothalamus and suprachiasmatic nucleus), brainstem reticular formation, and thalamus play central roles in sleep regulation. The ventrolateral preoptic nucleus (VLPO) promotes sleep through GABAergic inhibition of wake-promoting centers. REM and non-REM sleep alternate in cycles, regulated by a reciprocal interaction of cholinergic and monoaminergic neurons. Homeostatic and circadian influences, mediated by adenosine and melatonin respectively, help initiate and maintain sleep. Conclusion: Sleep is orchestrated by a complex but well-coordinated network of neural structures and chemical messengers. A better understanding of this system is essential for addressing common sleep-related disorders such as insomnia, hypersomnia, and narcolepsy.