Superior salivatory nucleus

The superior salivatory nucleus is one of the facial nerve nuclei, part of the parasympathetic nervous system, and is classified as a general visceral efferent nucleus. The neurons originating from the superior salivatory nucleus are known as preganglionic parasympathetic neurons. These neurons play a crucial role in controlling the function of the lacrimal gland (which produces tears) and the submandibular and sublingual salivary glands (which produce saliva).

These preganglionic neurons first travel through the facial nerve's sensory root, also called the nervous intermedius. They continue their journey through the facial nerve and pass through a small opening in the skull called the internal acoustic meatus.

• The nerve fibers destined to innervate the lacrimal gland bypass the geniculate ganglion and join a neural pathway known as the greater petrosal nerve. From there, they travel a considerable distance, synapse within the pterygopalatine ganglion, and ultimately reach and innervate the lacrimal gland.

• The remaining preganglionic parasympathetic neurons that do not pass through the greater petrosal nerve continue down the facial canal and exit through a branch of the facial nerve called the chorda tympani. The chorda tympani then connects with the lingual nerve, part of the mandibular nerve, allowing these neurons to travel along it. Eventually, they reach the submandibular ganglion, where they synapse. From this ganglion, postganglionic parasympathetic neurons innervate the submandibular and sublingual salivary glands. Through this complex pathway, the facial nerve helps control saliva production in the mouth.

The superior salivatory nucleus receives afferent input from the hypothalamus via descending autonomic pathways. These pathways enable the hypothalamus to directly influence the autonomic nervous system by establishing connections with both parasympathetic nuclei, such as the superior salivatory nucleus, and the sympathetic lateral horns of the spinal cord.