Sometimes I love to just nerd out on anatomy and physiology of the voice. The more I learn about how the voice works, the more it influences how I teach, and that ultimately makes me a better teacher. When I understand how the parts weave and dance around each other, I can better diagnose when things are a little off kilter and can very often come up with multiple ways to get to a solution. It is a fun way to teach!
This week I'm getting into the basics of the cranial nerves.
Cranial nerves originate directly from the brain or the top of the spinal cord. They are generally considered part of the parasympathetic nervous system, but that designation is a little fuzzy. That's beyond the scope of our discussion here today, but maybe at another time we can get into the weeds on that one.
The cranial nerves are connected to structures in the head, chest, and abdomen, and can be either motor nerves, sensory nerves, or both. They give the brain a TON of information about what's happening in the body, so we are using them all the time. There are twelve pairs of cranial nerves, each with its own specific function. We abbreviate them with the letters CN and a Roman numeral. For example, the Vagus nerve is cranial nerve ten, so you'll find it abbreviated to CN X.
For today's post, I'm going to list each of the cranial nerves and briefly describe it's function and how that relates to singing. Included at the bottom of this post is an infographic that you can download and print or share with students electronically. Students often love to learn about how their bodies work, and this is a simple way to educate them further about how integrated their singing is with their whole body and brain. Singing is a holistic activity!
CN I: Olfactory
This is really the only cranial nerve that doesn't have any direct involvement in singing because it's all about your sense of smell. Compared to the others, the olfactory nerves are short and go straight from the center of the brain to the nose. This nerve is entirely sensory with no motor component.
CN II: Optical
This nerve is also sensory only, and transmits visual information collected by the eyes to send to the brain for processing. We, of course, use this nerve to read music scores and to see our environment when we are performing. However, if this nerve is damaged, as many blind or visually-impaired singers have proven, we can adapt to learn music and perform differently.
CN III: Oculomotor
This motor nerve controls most of the muscles of the eye, so we can move our eyeballs around and dilate our pupils. This one is very important in our ability to focus on near objects like for reading, and for quickly being able to shift focus from near objects to far away objects.
CN IV: Trochlear
Another motor nerve for the eyes, this one controls the superior oblique muscle on the top of the eyeball (seriously, the structure of this muscle is pretty cool) and moves the eyeball down and in. We rarely only use one ocular muscle at a time, and often they are working on one side but not the other. When we use both superior oblique muscles at the same time, we end up crossing our eyes.
CN V: Trigeminal
Like the name suggests, this nerve has three main branches that go on the outside of the face below the eyes, in the cheek, and along the jaw. This nerve has both sensory and motor function by controlling chewing muscles and giving sensory information from the face to the brain. If you consider how sensitive your face is to touch, pressure, and temperature, you can know just how powerful this nerve is. Singing teachers love this nerve because it helps us to get our students to open their mouths when they sing. It's likewise also very important for diction.
CN VI: Abducens
The last of the motor nerves of the eyes, this nerve innervates the muscles on the side of the eye that rotate the eye away from the nose. When the actions of CNs III, IV, and VI work together, we are able to move our eyes all around and focus wherever we need to. Considering how many nerves are connected to our eyes, the brain takes all of that stuff very seriously!
CN VII: Facial
This motor nerve operates the muscles of the face, giving us the ability to express ourselves through facial movements. That's a very important part of performance! This nerve also has multiple branches, and depending on where those branches lie will determine if a person can raise one eyebrow independently of the other. (I can't. My eyebrows are knit together in solidarity, and there's nothing I can do about it because of where my nerves are.) This nerve can get infected and result in Bell's palsy, which is usually resolved after a time.
CN VIII: Vestibulocochlear
This sensory nerve is all about balance. It gets sensory information from your vestibular system in your inner ear that tells your brain where your body is in space and if it's in motion or standing still. This nerve doesn't help us sing any better, but it sure helps us stand upright on stage! This nerve is also confused easily, so vertigo can be a real issue for some folks.
CN IX: Glossopharyngeal
This nerve has both motor and sensory functions, and controls the salivary glands, taste in the back of the tongue and the pharynx. This muscle also controls a few small muscles in the throat and is responsible for our gag reflex. When we get nervous, sometimes this nerve is affected by our adrenaline and that can result in dry mouth and a feeling of tightness in the throat.
CN X: Vagus
The longest cranial nerve, this one is unusual because it's two branches aren't the same length. The other cranial nerves are basically symmetrical, but not this guy. The name comes from the Latin term for "wanderer" because it meanders through a person's torso, touching just about every major organ we have. It provides sensory information from the body to the brain, and also motor function to the larynx. This is every singer's favorite cranial nerve because it's what helps us make sound!
CN XI: Spinal Accessory
This motor nerve tends to drive singing teachers crazy, because it is the one that is responsible for allowing us to raise our shoulders. In other words, this nerve lets students hold their shoulders too high as they are trying to sing and breathe. It also innervates the sternocleidomastoid muscle, and lots of people hold tension in that muscle. However, it also allows us to roll our shoulders, which can be helpful for relieving some of that tension. So using those muscles well can help us to make friends with this nerve.
CN XII: Hypoglossal
The most important muscle for diction, this motor nerve innervates the muscles of the tongue. Weakness in either side can cause the tongue to deviate to one side or the other, which can effect the clarity of speech.
I hope this helps to illustrate again just how intricate the act of singing is when we think about neurological involvement. And believe me, I just scratched the surface here! Later this year I'll be working on an advance anatomy and physiology class to release that will include a big section on the neuro component of singing. Stay tuned for info on that, hopefully coming in the fall.
Just below you'll find an infographic that you can download and print to put in your studio or provide for your students so they can learn more about how their brain interacts with their singing. It's fascinating! And I think we can gain a whole lot more respect for our bodies when we learn just how hard they are working for us when we sing.
For a PDF of the infographic below, click the button below to download a printable file.