Cranial Nerves (Nursing)

00:01 Now, let's look at a different part of the peripheral nervous system called the cranial nerves.

00:07 Now, the cranial nerves are so named because they're actually exiting out of the cranium directly and there's 12 of them on either side and they're numbered from one to 12 generally speaking going from anterior to posterior.

00:27 Cranial nerve one is also called the olfactory nerve.

00:32 An olfactory is our fancy word for smell and the olfactory nerve in this case is actually a bunch of small nerves that sits in the superior aspect of the nasal cavity that pass through a thin portion of bone to reach a little bulb on the under surface of the brain.

00:53 Cranial nerve two is also called the optic nerve and it has a straight shot anteriorly into the back of the eyeball where it's going to merge with the retina and as you might guess, is going to be responsible for vision.

01:10 Nerves three, four, and six together make up what are called extraocular movement nerves.

01:21 So, cranial nerve three is called oculomotor. Four is trochlear and six is abducens and together, they control the directional movement of the eyeball.

01:34 Cranial nerve five is also called the trigeminal nerve because it has three major components, hence, the term trigeminal.

01:43 And sometimes, you'll see them represented by V1, V2, and V3.

01:49 The cranial nerve numbers always as a roman numeral and then, the suffix numeral is an Arabic numeral for the one, two, or three.

02:00 Trigeminal has a lot of functions since it is such a big nerve.

02:04 For example, it has a very important roles in the sensory innervation of the face.

02:10 It also controls some very important muscles such as the muscles of mastication, mastication means chewing.

02:17 So, these are the nerves that innervate our chewing muscles.

02:21 Cranial nerve seven is also called the facial nerve and they control a different set of muscles and these are called the muscles of facial expression.

02:33 And they're just what they sound like the ones that control facial expression, movements of closing and opening the eyelids for example, and areas around the lips and a much of the facial movements that you have when making, for example, emotional changes are expressed through these facial expression muscles.

02:56 Cranial nerve eight is called vestibulocochlear. And that's because it has sort of two functions and they're buried in the name there, vestibular and cochlear.

03:06 And essentially, what those are referring to are equilibrium and hearing.

03:14 Cranial number nine is a little bit of a weird one. It's called the glossopharyngeal nerve which is also very descriptive. Glosso referring to tongue, pharyngeal referring to pharynx and it has important sensory innervation of the posterior third of the tongue.

03:31 It also has something we're going to learn about called autonomic innervation of the parotid glad which is the largest salivary gland and it also innervates a muscle in the pharyngeal area and the pharyngeal muscles are generally involved in swallowing.

03:44 So, it has a little bit of everything. Cranial nerve 10 is called the vagus nerve and it's called the vagus nerve because it wanders throughout the body.

03:57 Vagus, for example, Vagabond, someone who wanders. It's wandering.

04:01 The vagus is a wandering nerve because it goes all over the place and it carries out a lot of functions.

04:08 It has some motor control, for example, pharyngeal muscles but it's really important for sensation and something called parasympathetic regulation of various internal organs, all the way down to the level of the transverse colon.

04:23 So, it leaves the head altogether and goes all the way down into the abdomen.

04:28 It innervates a lot of things along the way. Cranial nerve 11 is also called the accessory nerve and it's kind of a tricky one because it's actually originating from the spinal cord, coming up into the skull, and then, exiting again.

04:45 And, so, that's why we call cranial nerves,\cranial nerves as if they exit the skull.

04:49 It's not really coming directly off the brain like these other ones but it is still considered a cranial nerve.

04:55 The accessory nerve or cranial nerve 11 is really a motor nerve and that it innervates muscles that move the head, neck, and shoulders, things called the sternocleidomastoid and the trapezius muscles.

05:09 Finally, cranial nerve 12 is also called the hypoglossal nerve. And glossal refers to tongue.

05:16 So, the hypoglossal nerve innervates the majority of the tongue muscles.