Superimposed upon these metabolic demands and basic reflexes
Neurons in the parabrachial nucleus primarily increase the rate and depth of respiration, presumably in relation to emotional responses or in anticipation of metabolic demand during various behaviors.
Neurons located more ventrally in the intertrigeminal zone, between the principal sensory and motor trigeminal nuclei, produce apneas - necessary during swallowing and in response to noxious chemical irritation of the airway (e.g., smoke or water in the nasal passages).
The pathways that control vocalization in humans appear to originate in the frontal opercular cortex, which provides premotor and motor integration of orofacial motor actions.