Cranial Nerves: Introduction

00:01 Let's take an overview of the cranial nerves.

00:05 The cranial nerves will be discussed in greater detail as they come up throughout the head anatomy portion, but I think it's worth looking at all of them together to give you an idea of what they're doing overall.

00:18 To start, let's look at how they're numbered.

00:22 They're generally numbered from anterior to posterior, as they come off of the brain.

00:29 For example, cranial nerve one is actually very far anterior, and it's actually made up of many small nerves.

00:37 It's actually a bunch of tiny nerves that sit in the olfactory mucosa of the upper nasal cavity.

00:44 And they're going to carry out smell.

00:48 A little bit further back, we have the optic nerves, and they're carrying vision from the retina.

00:56 Cranial nerve III is the oculomotor nerve, so named because it innervates muscles that move the eyeball.

01:04 Cranial nerve IV called the trochlear nerve has to do with a tiny little pulley thing called the trochlea that's related to another one of the extra ocular muscles.

01:14 Similarly abducens, innervates a muscle that abducts the eye hence its name.

01:23 Cranial nerve V, the trigeminal nerve is so named because it has three separate branches ophthalmic maxillary and mandibular.

01:33 And it carries out both sensory and motor functions.

01:37 Cranial nerve VII innervates the muscles of facial expression and that's called the facial nerve.

01:45 Cranial nerve VIII, vestibulocochlear has both vestibular and cochlear functions meaning they're related to equilibrium and hearing.

01:55 Cranial nerve nine glossopharyngeal has areas of the tongue and pharynx that interacts with, it has both motor and sensory innervation as well hence its name the glossopharyngeal nerve.

02:10 The vagus nerve does a little bit of everything, sensation, parasympathetic, it has motor innervation and it goes all the way down to the colon.

02:22 So it's called vagus because it wanders like a Vega bond.

02:28 Cranial nerve XI, the accessory nerve is a little bit of a misnomer in the sense that it actually originates in the spinal cord, but it does enter the cranial cavity so that actually ends up exiting.

02:39 So that is really what makes it a cranial nerve because it exits the cranium, but it innervates two muscles that move the head, neck and shoulders.

02:51 Finally cranial nerve XII, hypoglossal, provides motor innervation to the tongue or glossus hence its name.

03:01 The cranial nerves can kind of be summarized here in terms of what they do most generally.

03:07 So we have somatic versus visceral, meaning sort of the body and things you can control versus organs.

03:15 That's what's meant by visceral.

03:17 We also have special senses that are carried out by the cranial nerves.

03:22 Those are things like vision or smell.

03:25 And as you can see, we have a nice summary here of which things are done by which nerves.