Anatomy and Chemistry Basics
The Nervous System
Cranial nerves are nerves of the PNS that originate from or terminate in the brain. There are 12 pairs of cranial nerves, all of which pass through foramina of the skull. Some cranial nerves are sensory nerves (containing only sensory fibers), some are motor nerves (containing only motor fibers), and some are mixed nerves (containing a combination of sensory and motor nerves). Characteristics of the cranial nerves, which are numbered from anterior to posterior as they attach to the brain, are summarized in Table 1.
|
Cranial Nerve |
Nerve Type |
Major Functions |
|---|---|---|
|
I: Olfactory |
sensory |
smell |
|
II: Optic |
sensory |
vision |
|
III: Oculomotor |
primarily motor |
eyeball and eyelid movement; lens shape |
|
IV: Trochlear |
primarily motor |
eyeball movement; proprioception (superior oblique muscle) |
|
V: Trigeminal: ophthalmic branch |
sensory |
sensations of touch and pain from facial skin, nose, mouth, teeth, and tongue; proprioception motor control of chewing |
|
V: Trigeminal: maxillary branch |
sensory |
sensations of touch and pain from facial skin, nose, mouth, teeth, and tongue; proprioception motor control of chewing |
|
V: Trigeminal: mandibular branch |
mixed |
sensations of touch and pain from facial skin, nose, mouth, teeth, and tongue; proprioception motor control of chewing |
|
VI: Abducens |
primarily motor |
eyeball movement; proprioception (lateral rectus muscle) |
|
VII: Facial |
mixed |
movement of facial muscles; tear and saliva secretion; sense of taste and proprioception |
|
VIII: Vestibulocochlear: cochlear branch |
sensory |
hearing |
|
VIII: Vestibulocochle-ar: vestibular branch |
sensory |
sense of equilibrium |
|
IX: Glosso-phayrngeal |
mixed |
sensations of taste, touch, and pain from tongue and pharynx; chemoreceptors (that monitor O2and CO2); blood pressure receptors; movement of tongue and swallowing; secretion of saliva |
|
X: Vagus |
mixed |
parasympathetic sensation and motor control of smooth muscles associated with heart, lungs, viscera; secretion of digestive enzymes |
|
XI: Accessory |
primarily motor |
head movement; swallowing; proprioception |
|
XII: Hypoglossal |
primarily motor |
tongue movement, speech, and swallowing; proprioception |
