Introduction:
Cranial nerves are a set of 12 pairs of nerves that originate from the brain and control various functions in the head and neck. Each cranial nerve has a specific function and innervates different structures in the body.

Mechanism of Action:

Sensory Function:
- Some cranial nerves, such as the olfactory nerve (CN I) and the optic nerve (CN II), are primarily sensory nerves.
- These nerves transmit sensory information from the nose (CN I) and the eyes (CN II) to the brain for processing.

Motor Function:
- Other cranial nerves, such as the oculomotor nerve (CN III) and the facial nerve (CN VII), are primarily motor nerves.
- These nerves control the movement of muscles in the eye (CN III) and the face (CN VII) for various functions like eye movement and facial expressions.

Mixed Function:
- Some cranial nerves, such as the trigeminal nerve (CN V) and the vagus nerve (CN X), have both sensory and motor functions.
- These nerves are involved in functions like chewing (CN V) and swallowing (CN X) as well as transmitting sensory information from the head and neck.

Function in Autonomic Nervous System:
- Certain cranial nerves, like the glossopharyngeal nerve (CN IX) and the vagus nerve (CN X), also play a role in the autonomic nervous system.
- These nerves regulate functions like heart rate, digestion, and respiratory rate.
In conclusion, cranial nerves play a crucial role in controlling various functions in the head and neck through sensory, motor, and autonomic functions.