The trigeminal nerve is the part of the nervous system responsible for sending pain, touch and temperature sensations from your face to your brain. It's a large, three-part nerve in your head that provides sensation. One section called the mandibular nerve involves motor function to help you chew and swallow.each of the fifth and largest pair of cranial nerves, supplying the front part of the head and dividing into the ophthalmic, maxillary, and mandibular nerves. The nerve has three divisions: the ophthalmic, maxillary, and mandibular nerves (Figure 61.1). The innervation includes the cornea and conjunctiva of the eye; mucosa of the sinuses, nasal and oral cavities; and dura of the middle, anterior, and part of the posterior cranial fossae.