the final learning objective for this module is to list and briefly describe the 12 cranial nerves the cranial nerves are 12 pairs of nerves that arise from the brain and brain stem making up part of the peripheral nervous system so each cranial nerve is identified with a number designated by Roman numerals and a name the numbers indicate the order from anterior to posterior in which the nerves arise the name designates the nerves distribution or their function three of the cranial nerves carry only sensory neurons and are called special Sensory neurons because they're associated with our special Senses of seeing hearing and smelling these are the old factory optic and vestibular copar nerves five cranial nerves are classified as motor nerves because they contain only axons of motor neurons as they leave the brain stem these neurons innovate sceletal muscles of the eyes and the tongue and include the ocular motor nerve the trar nerve the abducens nerve the accessory nerve and the hypoglossal nerve the remaining four cranial nerves are called mixed nerves because they contain aons of both sensory and motor neurons entering and exiting the brain stem these include the trigeminal facial glossop faral and the vagus nerves now I'm not going to go through each cranial nerve in detail but I did want to show you some of these nerves a little closer up so cranial nerve one is the old factory nerve it is entirely sensory and contains the axons that conduct nerve impulses for old faction or smell we will cover this again when we get to the special Senses in a few weeks but the olda factory receptors for smell sit within this olfactory epithelium this sits in the Superior part of our nasal cavity odorant or smells will dissolve in the mucus in the nose that then activates our receptors the nerve impulse runs then along our olfactory bulb thefactory tract which then makes up our olfactory nerve cranial nerve 2 is the optic nerve which again we will come back to when we look at the special senses and the optic nerve is another nerve which is entirely sensory carrying our nerve impulses for vision in the retina so this is our retina here which is the innermost layer of our eye we have receptors for vision called photo receptors more specifically these can either be rods or cones these rods and cones are stimulated by light which generates receptor potentials which travels along our bipolar cells to our gangan cells which then converge to form our optic nerve so you can see this is our optic nerve heading back to the brain there the last of our special sensory nerves which we'll come back to again is our cranial nerve eight and the vestibular cckar nerve so the vestibular clean nerve has two branches a vestibular branch which extends from the vestial in the inner ear and Carries our nerve impulses for equilibrium and the ccka branch which extends from the ccka and carries the nerve impulses for hearing so this structure and these structures here are our vable they make up our equilibrium receptors this coiled structure here is our ccka which carries our nerve impulses for hearing so these two branches then converge into our vestibular ccka nerve as an example of a purely motor nerve here we have cranial nerve 11 which is our accessory nerve and the accessory nerve conveys nerve impulses to the stoco mastoid and the trapezius muscles so these are muscles of the neck and the upper back or the shoulder region our Stern chloro mastoid muscles here and this is part of our trapezius here these muscles help coordinate our head and our neck movements lastly an example of a mixed nerve so a nerve which contains both motor and sensory axons is cranial nerve number seven or the facial nerve the sensory axons of the facial nerve extend from the taste buds of the anterior 2/3 of the tongue so the the front portion of the tongue from The receptors for touch pain and thermal Sensations from the skin in the ear canal so the hole in your ear and then also from proprioceptors in the muscles of the face and the scalp accents of the motor neurons innovate muscles of the inner ear the face the scalp and the neck and this allows for change in things like facial expression it can also help dampen or soften the sound waves that are entering the ear in the case of really loud noises now interestingly the facial muscle actually actually innovates more sceletal muscle than any other nerve in the whole body now just to be clear I don't need you to be able to regurgitate the exact makeup and function of each of these 12 cranial nerves however I do want you to understand what makes a cranial nerve a cranial nerve to understand how they are numbered and named and whether they are made up of a sensory neuron a motor neuron or both now when some of you move on in your degrees you'll need to understand in more detail the function of each of these cranial nerves however this is not something that I will test you on in this unit that being said I have put together this summary table of the cranial nerves I'm not going to read it out to you but you might like to make up something similar as part of your own revision I also want to note that some of the cranial nerves have much more extensive functions than I've listed here so this is just an example of some of those functions but one tool that might help you remember some of the information that you could be tested on and this is the stuff that I I really do want you to remember and that could be using the tool of a pneumonic and a pneumonic is a memory or a learning technique that helps individuals remember information more easily it can take the form of an acronym it could be a rhyme or it could be a sentence where the first letter of each word in that sentence as an example corresponds to the first letter of the word that you're trying to remember so if we take a look at this list here on the left and we have the sentence on on on on they traveled and found Voldemort guarding very ancient H cruxes now this sentence obviously Harry Potter themed I chose this sentence as it's one of the more PG versions I've come across but the first letter of each of the words in the sentence corresponds to the first letter of the name of each of those cranial nerves in order so we have on Old Factory on optic on ocul motor they trar as an example the second column A Little Less PG but something that's a bit silly and therefore easy to remember and the first letter of each of the words in this sentence correspond to whether the cranial nerve is sensory is motor or is both so a mixed nerve so we have some say marry money but my brother says big boobs matter more so some sensory say sensory marry motor but both