The nerves that run your face

Twelve pairs of cranial nerves come straight from your brain. Meet the ones that let you see, smile, chew and swallow.

5 minutes · 6 stops

Seeing
The optic nerve carries about a million nerve fibres from the back of each eye to your brain. Where it leaves the eye there are no light sensors, so each eye has a blind spot, which your brain quietly fills in.
Moving your eyes
Three cranial nerves move your eyes. The oculomotor nerve does most of the work, and also lifts your eyelid and narrows your pupil in bright light, which is why doctors shine a torch in your eyes after a head injury.
Feeling your face
The trigeminal nerve carries touch and pain from your whole face, teeth and the inside of your mouth through three branches. It also powers your chewing muscles. Dentists numb one of its branches before working on your lower teeth.
Smiling and frowning
Every expression you make is controlled by the facial nerve. It fans out across your face to dozens of small muscles attached to the skin. When it stops working, as in Bell's palsy, one side of the face droops.
Swallowing and speaking
The vagus nerve wanders from your brainstem all the way to your gut. On the way it controls your voice box and helps you swallow, and lower down it slows your heart and runs your digestion.
Your tongue
The hypoglossal nerve moves your tongue. If one side is damaged, your tongue points towards the weak side when you stick it out, a simple test doctors use in a neurological examination.