A dense cluster of pigmented, noradrenergic neurons lying in the dorsolateral pontine tegmentum beneath the floor of the fourth ventricle projects diffusely throughout the cortex and is implicated in arousal and attention. Which structure is described?

• A Raphe nuclei
• B Pedunculopontine nucleus
• C Substantia nigra, pars compacta
• D Locus coeruleus ✓

Explanation

The locus coeruleus is the largest collection of noradrenergic neurons in the brain, located in the dorsolateral pons, and sends widely divergent projections to virtually the entire neuraxis, regulating arousal, attention and the sleep-wake cycle. The raphe nuclei are serotonergic, the substantia nigra pars compacta is dopaminergic and concerned with basal ganglia function, and the pedunculopontine nucleus is cholinergic, so their transmitter profiles exclude them.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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