Physiology of sleep

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Share on Pinterest Illustration by Brittany England It’s no secret that sleep is one of the most important activities for good health. When we • repair muscles • grow bones • manage hormones • sort memories Sleep can be broadly segmented into rapid eye movement (REM) sleep and non-REM (NREM) sleep. Most adults will enter sleep from the drowsy state into NREM sleep. NREM sleep is divided into three sub-stages: stage N1, stage N2, and stage N3. Older classification had four stages of NREM sleep. In the current rules, NREM stage 3 and NREM stage 4 are combined as stage N3. Sleep stages occur in cycles lasting 90 to 120 minutes each. Four to five cycles occur during a typical night of sleep. Shifting of stages occurs over the course of the night, typically with an increased percentage of NREM sleep in the first half of the night and an increased percentage of REM sleep in the second half of the night. In this article, we’ll explore these stages of sleep, discuss • Non-REM sleep happens first and includes three stages. The last stage of non-REM sleep is when you sleep deeply. It’s hard to wake up from this stage of sleep. • REM sleep happens about an hour to an hour and a half after falling asleep. REM sleep is when you tend to have vivid dreams. NREM Stage N1 This stage of non-REM sleep is the typical transition from During this stage: • Eye movements are typically slow and rolling. • heartbeat and breathing slow down • muscles begin to relax • you produce low amplitude mixed ...

The integrated activity of the autonomic nervous system (ANS) with the somatomotor and the neuroendocrine systems allows an animal to maintain and regulate its interaction with the external environment. Significant changes in ANS activity occur on passing from wakefulness to sleep, and this pattern of autonomic activation is profoundly different even between Section snippets Autonomic nervous system: anatomy and function The peripheral portion of the autonomic nervous system (ANS) consists of 3 subdivisions, the parasympathetic, the sympathetic, and the enteric nervous systems (ENS). While the ENS exclusively controls the function of the gastrointestinal system, the sympathetic and parasympathetic nervous systems i) control the activity of cardiac cells, smooth muscle cells, and exocrine and endocrine gland cells; ii) exert distinct metabolic effects, and iii) affect immune function. The sympathetic and ANS activity during wake and sleep Wake and sleep are behaviors that are characterized by different levels of engagement with the external environment; accordingly, a consistent remodulation of autonomic nervous system (ANS) activity occurs on passing from wake to sleep [3]. Furthermore, sleep itself is a state that shows an intrinsic heterogeneity in terms of physiological control. During non-rapid eye-movement sleep (NREMS), physiological regulation clearly operates according to the ‘homeostatic’ modality. In accordance with Autonomic function, sleep disorders, and immune...

Acute stress is a fundamental adaptive response which enables an organism to cope with daily threatening environmental stimuli. If prolonged and uncontrollable, the stress response may become inadequate and ultimately result in health damage. Animal models of stress in rodents indicate that both acute and chronic stressors have pronounced effects on sleep architecture and circadian rhythms. One major physiological response elicited by stress is activation of the hypothalamo-pituitary-adrenal axis. In both animals and humans, the hypothalamo-pituitary-adrenal axis plays an important role in sleep–wake regulation and in alterations of the sleep–wake cycle secondary to exposure to acute or chronic stressors. In humans, dysfunction of the neuroendocrine regulation of sleep can lead to severe sleep disturbances. The progressive decay of the hypothalamo-pituitary-adrenal axis in elderly people, which mimics chronic exposure to stress, may contribute to fragmented and unstable sleep in ageing. Shift workers, chronic insomniacs or patients suffering from mental disorders show abnormal hypothalamo-pituitary-adrenal secretory activity and concomitant sleep disturbances. Those sleep disorders and possible underlying mechanisms are briefly reviewed. • Previous article in issue • Next article in issue

The objectives of this review were to explain the neurologic processes that control the human sleep–wake cycle as well as the pathophysiology of the human circadian clock. Non-rapid eye movement and rapid eye movement sleep are the two main phases of sleep. When triggered by circadian input from the anterior hypothalamus and sleep–wake homeostatic information from endogenous chemical signals (example, adenosine), the ventrolateral preoptic nucleus initiates the onset of sleep. Arousal in which there is a conscious monitoring of the surroundings and the ability to respond to external stimuli is known as wakefulness. It contrasts the state of sleep, in which receptivity to external stimuli is reduced. The higher the synchronous firing rates of cerebral cortex neurons, the longer the brain has been awake. Sleep–wake disturbances induced by endogenous circadian system disruptions or desynchronization between internal and external sleep–wake cycles are known as circadian rhythm sleep–wake disorder (CRSWD). Patients with CRSWD usually report chronic daytime drowsiness and/or insomnia, which interferes with their activities. CRSWD is diagnosed based on the results of some functional evaluations, which include measuring the circadian phase using core body temperature, melatonin secretion timing, sleep diaries, actigraphy, and subjective experiences (example, using the Morningness–Eveningness Questionnaire). CRSWD is classified as a dyssomnia in the second edition of t...

Contents • 1 Introduction • 2 What is Sleep? • 3 History of Sleep Science • 4 Concepts around Sleep • 5 Sleep Regulation • 6 Function of Sleep • 6.1 Restorative Theory • 6.2 Cognitive Function Theory • 6.3 Energy Conservation Theory • 6.4 Adaptive Theory • 7 Physiology of Sleep • 7.1 Assessment of Sleep • 7.1.1 Medical Assistance Methods • 7.1.2 Self-Assessment Methods • 7.2 Sleep Stages • 7.2.1 NREM Sleep Stage 1 (N1) • 7.2.2 NREM Sleep Stage 2 (N2) • 7.2.3 NREM Sleep Stage 3 (N3) • 7.2.4 REM Sleep • 8 Anatomy of Sleep • 9 Resources • 10 References Introduction [ | ] Sleep is an important part of our daily routine. It is estimated that we spend about a third of our time sleeping. • Quality sleep is just as important for good health as proper • Sleep is important to many brain functions, we need sleep to learn effectively and it has been shown that a lack of sleep affects our concentration levels negatively. • Evidence also shows that sleep affects almost every type of tissue and system in the body and that a chronic lack of sleep can increase the risk for Sleep is vital to good health! What is Sleep? [ | ] Sleep can be defined as “an active state of unconsciousness produced by the body where the brain is in a relative state of rest and is reactive primarily to internal stimulus." • low physical activity levels • reduced sensory awareness Sleep is also regulated by the circadian rhythm and homeostatic mechanisms. Furthermore, certain Multiple areas in the brain work togeth...