Final answer:
The pontine/medullary raphe nuclei are involved in regulation of sleep-wake cycles and mood through the release of serotonin. Serotonergic neurons in these nuclei project to brain regions involved in cognition and mood.
Step-by-step explanation:
The pontine/medullary raphe nuclei are involved in various physiological processes, including regulation of sleep-wake cycles and mood. These nuclei contain serotonin-immunoreactive cells, which release the neurotransmitter serotonin (5-HT) to modulate neuronal activity throughout the brain and spinal cord. Serotonergic neurons in the raphe nuclei have extensive projections to areas involved in cognition and mood, such as the frontal cortex and limbic system.