[Neural Circuit of Tear Secretion].

Tears are extracellular fluid secreted by the lacrimal apparatus. Tear secretions have three secretory modes, and each mode has different roles. Basal secretion, a continuous flow, moistens the surface of the cornea. Reflex tearing, a marked transient secretion, removes foreign bodies or irritant chemicals from the ocular surface. Emotional secretion, which occurs due to emotional arousal. Although the regulation of the lacrimal gland activity via the autonomic nervous system has been recognized as fundamental to maintaining the aqueous tear flow, the contribution of the individual neural system in tear secretion has not been elucidated.