Muscles affected:
Buccinator
Action: Compresses the cheeks against the teeth
Frontalis (Frontal Belly of Occipitofrontalis)
Action: Raises the eyebrows and wrinkles the forehead.
Orbicularis Oculi
Action: Closes the eyelids
Platysma
Action: Depresses the mandible and pulls the lower lip down and outward
Zygomaticus Major
Action: Elevates the corners of the mouth
Mechanism of Muscle Weakness:
Bell's palsy is the paralysis or weakness of facial muscles due to injury, inflammation, or damage to the facial nerve (cranial nerve VII). This causes a lack of voluntary control over facial movements on the affected side because the muscles are paralyzed due to the nerve's failure to transmit signals.
Other Symptoms of Facial Muscle Weakness:
Drooling
Loss of sense of taste
Hypersensitivity to sound
Dryness of the eye