Humans and other mammalian species possess an endogenous circadian clock system that has evolved in adaptation to periodically reoccurring environmental changes and drives rhythmic biological functions, as well as behavioural outputs with an approximately 24‐hour period. In mammals, body clocks are hierarchically organized, encompassing a so‐called pacemaker clock in the hypothalamic suprachiasmatic nucleus (SCN), non‐SCN brain and peripheral clocks, as well as cell‐autonomous oscillators within virtually every cell type. A functional clock machinery on the molecular level, alignment among body clocks, as well as synchronization between endogenous circadian and exogenous environmental cycles has been shown to be crucial for our health and well‐being. Yet, modern life constantly poses widespread challenges to our internal clocks, for example artificial lighting, shift work and trans‐meridian travel, potentially leading to circadian disruption or misalignment and the emergence of associated diseases. For instance many of us experience a mismatch between sleep timing on work and free days (social jetlag) in our everyday lives without being aware of health consequences that may arise from such chronic circadian misalignment, Hence, this review provides an overview of the organization and molecular built‐up of the mammalian circadian system, its interactions with the outside world, as well as pathologies arising from circadian disruption and misalignment.

中文翻译：

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哺乳动物昼夜节律系统：组织和现代生活挑战

人类和其他哺乳动物物种拥有内源性生物钟系统，该系统已经进化以适应周期性重复发生的环境变化并驱动有节奏的生物功能，以及大约 24 小时的行为输出。在哺乳动物中，生物钟是按层次组织的，包括下丘脑视交叉上核 (SCN) 中所谓的起搏器时钟、非 SCN 大脑和外周时钟，以及几乎所有细胞类型中的细胞自主振荡器。分子水平上的功能时钟机制、生物钟之间的对齐以及内源性昼夜节律和外源性环境周期之间的同步已被证明对我们的健康和福祉至关重要。然而，现代生活不断对我们的内部时钟构成广泛的挑战，例如人工照明、轮班工作和跨经络旅行，可能会导致昼夜节律紊乱或失调以及相关疾病的出现。例如，我们中的许多人在日常生活中都经历过工作时间和空闲时间（社交时差）的睡眠时间不匹配，而没有意识到这种慢性昼夜节律失调可能导致的健康后果，因此，本次审查提供了该组织的概述和哺乳动物昼夜节律系统的分子结构、其与外界的相互作用，以及由昼夜节律紊乱和失调引起的病理学。