Locus coeruleus noradrenaline — MRCPsych Paper A MCQ

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ModerateNeuroanatomyLocus coeruleus noradrenalineMRCPsych Paper A

A 40-year-old woman with post-traumatic stress disorder has persistent hypervigilance and an exaggerated startle response. These features are associated with excessive activity in a compact dorsal pontine nucleus that has widespread ascending projections and regulates arousal, attention and responses to salient stimuli. Which nucleus is described?

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Correct answer: E — Locus coeruleus

The correct answer is E, the locus coeruleus. This compact nucleus in the dorsal pons is the origin of the major ascending noradrenergic pathway, with widespread projections to cortical and limbic regions. Its activity modulates wakefulness, attention, responses to salient stimuli and stress-related arousal, making it the best match for hypervigilance in PTSD. The dorsal raphe is predominantly serotonergic. The nucleus basalis of Meynert is a basal forebrain cholinergic nucleus involved particularly in cortical attention and cognition. The ventral tegmental area is a midbrain dopaminergic nucleus central to reward and salience. The tuberomammillary nucleus is a hypothalamic histaminergic arousal nucleus, but it is not the source of the principal ascending noradrenergic pathway.

Reference: Royal College of Psychiatrists, Paper A mapping, section 3.4.6: The anatomical course of major neurochemical pathways, current webpage. https://elearninghub.rcpsych.ac.uk/catalog?pagename=Paper_A_mapping