Final answer:
If the facial nerve is injured, eye closure, elevation of the mouth corner, and wrinkling of the forehead would be impaired. Head turning and mastication are controlled by other nerves, namely the spinal accessory nerve and the trigeminal nerve, hence they would not be affected by a facial nerve injury.
Step-by-step explanation:
If the facial nerve is injured, certain movements will be impaired which are associated with the muscles that it controls. The movements that would be specifically affected include:
Eye closure, which involves muscles like the orbicularis oculi for blinking and shutting the eyes.
Elevation of the mouth corner, which is controlled by muscles such as the zygomaticus major and minor for smiling.
Wrinkling of the forehead, which is done by the frontalis muscle and is part of the facial expression.
Movement such as head turning is largely controlled by the sternocleidomastoid muscle, which is innervated by the spinal accessory nerve, not the facial nerve.
Mastication (chewing) involves muscles like the masseter and temporalis, and these are controlled by the trigeminal nerve. Therefore, these latter movements would typically not be affected by facial nerve injury.