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Suprachiasmatic nucleus
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The tiny suprachiasmatic nucleus, measuring less than 1mm3, is one of many hypothalamic nuclei that regulate several important body functions. As its name suggests, it is located within the upper portion of the optic chiasm and serves as the primary regulator of circadian rhythms in the brain. It is sometimes referred to as the 'master circadian pacemaker' or the 'central clock'.
The suprachiasmatic nucleus consists of two key regions: ventrolateral and dorsomedial subdivisions. The ventrolateral subdivision receives direct input from the retina, which tunes it to the actual length of the day. Additionally, it receives general input from parts of the brainstem and thalamus. The dorsomedial subdivision, on the other hand, receives fewer inputs, primarily from various nuclei of the hypothalamus or the adjacent regions.
By influencing endocrine, autonomic, and behavioral functions, including the regulation of melatonin release by the pineal gland, the suprachiasmatic nucleus is key in establishing the normal sleep-wake cycle. Additionally, it plays a significant role in regulating day-night cycles across various physiological processes including motor activity, body temperature, plasma hormone levels and renal secretion.
| Terminology |
English: Suprachiasmatic nucleus Latin: Nucleus suprachiasmaticus |
| Definition | Primary circadian rhythm regulator of the brain |
Learn more about the suprachiasmatic nucleus of the hypothalamus in the following study unit:
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