Cranial nerve pathways

Not only are there 12 cranial nerves with unique functions, each cranial nerve also has its own unique pathway from where it begins to where it ends. All this information can surely make your brain explode, but we are going to break it down for you!

Simply put, cranial nerves connect centrally to cranial nerve nuclei which is where cranial motor nerves begin, or where cranial sensory nerves terminate. Remember, nerve fibers leaving the brain are considered efferent fibers, where nerves fibers entering the brain are considered afferent fibers. These centrally located nuclei contain the cell bodies of motor and sensory neurons of the cranial nerves, and the nuclei are where these neurons will synapse with the neurons of higher brain centers such as the thalamus and cerebral cortex.

So essentially, these nuclei act as a pit stop for the exchange of signals travelling between higher brain centers such as our cerebral cortex, to all of the structures our cranial nerves go on to innervate, ultimately facilitating the function of the cranial nerves. This is important as the cranial nerves will carry different types of motor and sensory information, so the nuclei help organize all this information.

In short, cranial nerves can carry two types of motor information, the first being somatic and branchial motor information, and the second being visceral motor or parasympathetic motor information. Then there are the three types of sensory information, the first being somatic sensory information, the second is visceral sensory information, and the third is special sensory information. So, we used the analogy before that cranial nerve pathways are like highways, so let’s talk about these highways and how they transmit the information carried along cranial nerves from the brain centrally to our head, neck, and body peripherally.

Let’s begin by talking about the cranial nerves that carry somatic motor fibers and branchial motor fibers, which eventually go on to innervate voluntary muscles. Of note, the difference between somatic and branchial motor is that branchial motor fibers are just fibers that innervate structures derived from the pharyngeal arches, which are also sometimes called the branchial arches.