Locus coeruleus
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![Micrograph showing the locus coeruleus (upper-right of image) in an axial section of the pons. The fourth ventricle (quasi-triangular white area) is in the upper-left of the image. The midline is seen on the left. The large white area in the upper-left corner is where the cerebellum would be. HE-LFB stain.Locus coeruleus highlighted in green.](/Images/godic/202501/30/Locus_ceruleus_-_very_low_mag3658.jpg")
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The locus coeruleus (\-si-ˈrü-lē-əs\, also spelled locus caeruleus or locus ceruleus) is a nucleus in the pons (part of the brainstem) involved with physiological responses to stress and panic.
The locus coeruleus is the principal site for brain synthesis of norepinephrine (noradrenaline). The locus coeruleus and the areas of the body affected by the norepinephrine it produces are described collectively as the locus coeruleus-noradrenergic system or LC-NA system. Norepinephrine may also be released directly into the blood from the adrenal medulla.