<- [[Cognitive Science and AI MOC]] # Circadian Rhythms ## Definition/Description Circadian rhythms are the physical, mental, and behavioral changes that follow a 24-hour cycle, responding primarily to external cues like light and darkness. These rhythms are driven by the body’s internal biological clock, which regulates processes such as sleep-wake cycles, hormone release, body temperature, and metabolism. ## Key Points - **Biological Clock**: The master control for circadian rhythms is located in the **suprachiasmatic nucleus (SCN)**, a region in the hypothalamus of the brain. The SCN receives input from the eyes to synchronize the body's internal clock with the external environment, particularly the day-night cycle. - **Light as a Primary Cue**: Light exposure, especially in the morning, helps reset the body’s internal clock each day. The presence of light activates photoreceptors in the eyes, sending signals to the SCN, which then adjusts various physiological processes, including the release of melatonin. - **Melatonin**: Known as the "sleep hormone," melatonin is produced by the **pineal gland** in response to darkness. Melatonin helps induce sleep by lowering body temperature and preparing the body for rest. - **Sleep-Wake Cycle**: Circadian rhythms regulate the sleep-wake cycle, with most people experiencing a natural dip in alertness during the night and a peak during daylight hours. Disruptions to this rhythm, such as shift work or jet lag, can lead to sleep disturbances and other health issues. - **Temperature and Metabolism**: Body temperature follows a daily rhythm, typically peaking in the late afternoon and dipping in the early morning. Metabolic processes, such as the regulation of glucose and fat metabolism, also follow circadian patterns, influencing energy use and weight management. - **Circadian Rhythms and Cognitive Function**: Cognitive performance, including attention, memory, and decision-making, is influenced by the time of day due to circadian rhythms. People tend to perform best cognitively during their natural peak hours, which vary from person to person. - **Disruption and Health Impacts**: Disruptions to circadian rhythms, such as irregular sleep patterns, shift work, or crossing multiple time zones, can lead to various health problems, including sleep disorders, cardiovascular disease, metabolic syndrome, and mood disorders. - **Chronotypes**: Different individuals have different natural circadian rhythms, which are often categorized as **morning people (larks)**, **evening people (owls)**, or **intermediate** types. These variations are influenced by genetics, age, and lifestyle. ## Connections - Related notes: [[Neuroscience of Sleep]], [[Sleep and Learning]], [[Memory Consolidation in Sleep]] - Broader topics: [[Biological Rhythms]], [[Health and Wellness]] ## Questions/Reflections - How can knowledge of circadian rhythms be applied to improve workplace productivity and well-being? - What are the potential long-term health effects of sustained circadian rhythm disruptions, particularly in shift workers? ## References (Add relevant studies, research, or resources on circadian rhythms here.)