 Hey everybody, Dr. O here, in this video we're going to cover the second six pairs of the 12 cranial nerves. So we're going to start here with cranial nerve seven, the facial nerve. This is a mixed nerve, meaning it has both a sensory and motor function. So a big picture, its sensation is going to be to the anterior two thirds of the tongue and it's going to be motor to the muscles of facial expression. So let's go ahead and take a look here. So again if you want to, it's in charge of the taste receptors on the anterior two thirds of the tongue, not the entire tongue. So if you want to assess the sensory function of this nerve, you would need to test the sensation of the anterior two thirds of the tongue. And then for motor, it's the muscles of facial expression primarily. So what I would do is have someone make funny faces, right? Crinkle their eyebrows and do those types of things. So if they can use the muscles of facial expression, then cranial nerve seven is working. Now it does also have a visceral motor control. So tear and nasal mucus glands and some of the salivary glands. So there'd be another function there as well. A big picture, its sensation to the anterior two thirds of the tongue and motor to the muscles of facial expression. Next we have the vestibular cochlear nerve, cranial nerve eight. So this is going to have two branches. This is going to be a purely sensory cranial nerve. It's going to have a vestibular branch, which is involved in balance and equilibrium and the cochlear branch involved in hearing. So maybe you don't know this yet, but the cochlea is where we hear and the vestibular is where balance and equilibrium come from. So the vestibular cochlear nerve. So that's, like I said, the vestibular branch is going to control the vestibule there. What you see there in the image on the right labeled as the saccule and the utricle, that location is going to be the vestibule. And that's going to be where balance and equilibrium come from. Then that cochlear branch, that cool cochlear shape there, that's going to be where we hear. So vestibular cochlear branch, we have balance, equilibrium and hearing. So if you want to assess the function of this cranial nerve, any kind of balance testing, asking questions about balance and equilibrium, assessing hearing, pretty easy to do. You can use tuning forks or fingers, these types of things. That's the vestibular cochlear nerve, cranial nerve eight. Next we have cranial nerve nine, the glasso farangio nerve. This is a mixed nerve that has both a sensory and motor function. So sensation is going to be the posterior third of the tongue. So if you're assessing the sensation of the taste receptors of the tongue, you're actually assessing both cranial nerves seven and nine. And then for motor, it's going to be the muscles of the pharynx or the throat involved in swallowing. So if you want to assess the function of the glasso farangio nerve, assess that posterior third of the tongue, and then also anything involved in swallowing. So you can ask a patient to swallow, ask if they're having any difficulty swallowing. Now swallowing and the gag reflex and these types of things, you really are assessing the function of more than one cranial nerve. But if you see a problem there, you would know you'd have it narrowed down where to look. So that's the glasso farangio nerve, sensation to the posterior third of the tongue, motor to the muscles involved in swallowing there in your pharynx. Next we have cranial nerve 10, which many would argue would be the most important cranial nerve. So it's called the vagus nerve, which means wanderer. This is going to be about 75% of the parasympathetic nervous system is this one nerve. This is a mixed nerve with both sensory and motor functions. So big picture, it's just all the sensation and organ control of the thoracic and abdominal pelvic cavity. So it actually has more functions than that. But it starts up in the throat. But this is so sensation, parts of the pharynx. So it shares the job with cranial nerve nine. The external acoustic canal is going to be involved here. But real big picture, just sensation to the visceral organs of the thoracic and abdominal pelvic cavities. And the same thing with motor. It does play a role in controlling the palate in your pharynx. So the gag reflex would actually be assessing cranial nerves nine as well as 10, but then the digestive, respiratory and cardiovascular systems in your thoracic and abdominal cavity. So it just has a massive amount of control. So that's cranial nerve 10, vagus nerve or the wanderer. Next we have cranial nerve 11, which is the accessory nerve, also known as the spinal accessory nerve. This is going to be a purely motor nerve. Its big function is that it helps control the muscles of the upper back. Specifically, and the ones I'll ask you to know, the sternocleidomastoid and the trapezius muscles. But it does control some other muscles because there are two branches. So the internal branch actually joins the vagus nerve and helps control the palate, pharynx and larynx. So now we're looking at the gag reflex and swallowing being cranial nerves nine, 10 and 11. But we really care about the external branch which travels down and controls these two muscles here, sternocleidomastoid and the trapezius. So if you have someone shrug their shoulders to assess the function of the trapezius for the sternocleidomastoid, I would always have a patient try to flex their head against my hands here and then also rotate. Because my one sternocleidomastoid muscle rotates the head both together, neck flexion, so simple muscle testing can assess the function of cranial nerve 11, the accessory or spinal accessory nerve. Last one, cranial nerve 12 is the hypoglossal nerve, glasomening tongue. This is going to be a purely motor cranial nerve that controls the muscles of the tongue. So the hypoglossal nerve controls voluntary control over the movement of the tongue. Obviously your tongue does a lot of things subconsciously or involuntarily when you're chewing and swallowing these type of things, but voluntary control the tongue. So probably the simplest one to test, have someone stick their tongue out at you. If it comes straight out, cranial nerve 12 is working fine. If one of the two of the cranial nerve 12 pair are not functioning properly, the tongue will deviate towards the weak side. So I've seen this, if someone sticks their tongue out and it shoots off to the right, that means the cranial nerve 12 on the weak side is not functioning properly. Okay, so those are your 12 pairs of cranial nerves. Make sure you watch both parts of this video series. I hope this helps. Have a wonderful day. Be blessed.