Final answer:
The salivary nuclei receive input from the palate and tongue, mediated through the facial and glossopharyngeal nerves. Parasympathetic stimulation ensures a baseline level of saliva is maintained, keeping the mouth moist.
Step-by-step explanation:
Input to the salivary nuclei in the brainstem, which regulate salivation, comes from nerve impulses from taste buds on the palate and tongue. These impulses are conducted to the salivary glands, stimulating saliva secretion. The parasympathetic stimulation keeps the mouth moist. Key nerves involved in the process are the facial and glossopharyngeal nerves. The parasympathetic fibers of the facial nerve synapse in the pterygopalatine ganglion, influencing the submandibular and sublingual glands, while those of the glossopharyngeal nerve synapse in the otic ganglion, affecting the parotid gland. Salivation is increased in response to food due to a visceral reflex arc and is also influenced by stimuli such as the sight and smell of food, coordinated through the hypothalamus.