hey everyone welcome to professor long's lectures in anatomy and physiology i'm professor bob long if you're watching these videos these videos are intended for use by students who are enrolled in my human anatomy and physiology courses at del mar college if anyone else finds them helpful great but know that the curriculum and the delivery is designed for those students preparing for my exams in my class you guys know when the coronavirus shut down so i'm doing videos online for my students to get instructional delivery this particular video is for my human anatomy and physiology 2 students we've been doing all the senses sensory physiology hopefully you've watched all the general sensory general sensory videos you've watched the special senses of olfaction gustation and you've watched this series of visual physiology this video is going to start the sensory physiology of equilibrium and hearing which are done by the inner ear so i'm going to do some setup and then we're going to go into the notes we'll be following along on page 18 of my note set if you're one of my students so now if you look at the inner ear model from lab you know that there's one part of the inner ear that coils around on itself and these coils end up bulging out into a large area this area is going to have three big loops one of them is going to come kind of forward and where they join this area here there's a swelling there's another loop that's going to lie on its side and it's going to have an enlarged area here and they're going to join together in this structure there would be a third loop running this way and i haven't drawn it all the way around it's a little bit hard to draw and keep it visually appealing this structure here is called the cochlea this area in the middle is called the vestibule and then these three structures are referred to as the semi circular canals because they're like half a circle and they're canals i usually abbreviate these as scc just for simplicity as my shorthand now before i go too far into this one of the things i want you guys to know and by the way each semicircular canal gets a name the one that is coming front to back would be our anterior semicircular canal the one that's lying on its side is called the lateral semicircular canal and the one that you can see through if you're looking at the model this way would be called the posterior semicircular canal we're going to talk about those now the inner ear really is sort of this maze of bone called the bony labyrinth you'll see this term labyrinth which means amaze like if you get lost in a maze of things now there's a bony labyrinth and a membranous labyrinth we've covered a little bit a bit of this in lab but i want to get this concept across to you before i go into detail here so imagine all you all know what pvc pipe is the clear i'm not the clear the white plastic piping that makes a plumbing so if i took a tube of pvc pipe and i capped the end of it off i could actually fill the pipe with some fluid maybe some pink kool-aid or something some hawaiian punch or something now what if i took a long blue light blue water balloon filled with water and i suspended it in here so that it's floating in the fluid so i have a hard plastic covering and i've got a soft flexible balloon in here the fluid that is outside the balloon that is filling the space between the balloon and the um pvc piping would go all the way around the balloon this way and around the back side filling all of it so it's completely surrounded and suspended and floating in a tube of fluid and then there would be some fluid inside the balloon well that's how the inner ear is set up now imagine if i took this pvc pipe and i coiled it around on itself like this everywhere the pvc pipe goes the balloon goes and follows it and the fluid inside the balloon would stay inside the balloon even though it's curved around and the fluid outside the balloon would still be surrounding it only now we can start to twist it around and knot it up well the pvc piping represents the bony labyrinth the thin shell of bone that makes the shape of the inner ear if i could slice the inner ear open there would be a tube like membranous structure going all around inside of here where it reaches these enlargements each one of these enlargements is called an ampulla so everywhere where one of the semicircular canals joins the vestibule it's called an ampulla well wherever the bone goes if it if it bulges out so does the membranous labyrinth and so i would have the membranous labyrinth and the bony labyrinth following each other like this now where these areas are here they're actually going to join or spread out here they'll form two bumps and then the membranous labyrinth would also continue inside the cochlea all the way around so now i have two mazes i have a bony labyrinth on the outside and i have a membranous labyrinth following it everywhere the fluid that goes around the membranous labyrinth or between the bony and membranous labyrinth there's a fluid called perilymph the fluid inside the membranous labyrinth would be a fluid called endolymph now lymph is a term for a clear it's a colorless fluid that is filtered out of our blood and as i stated in previous videos all of our cells have a range of homeostatic conditions under which they operate some cells have a very broad range of oxygen and glucose and calcium and sodium and you know nutrient concentrations some cells have a very narrow range of homeostatic conditions they have to have everything perfect the biggest wimps and weenies in the human body are neurons because neurons can't handle some of the other stuff in our blood we have to specially filter our blood to feed the neurons they put their waste in it and then we reabsorb it in our most of our nervous system we call it cerebrospinal fluid and it's filtered out of blood vessels called the cholera plexus in the eyeball we called it aqueous humor in the inner ear we call it endolymph and perilymph okay so now inside the membranous labyrinth is endolymph outside of it everywhere it goes would be perilymph those fluids are really important because they're going to trigger the senses of equilibrium in hearing and so a lot of this is explained at the top of page 18 as far as the anatomy so now i'm going to erase some of this over here because i want to be able to write some more detail and draw out what's going to happen so that we can understand equilibrium and we can understand the process of hearing now one of the things we do know is that the cochlea itself is going to monitor what we call audition or hearing inside the cochlea are cells that have little cilia that we call hair cells but they're really silly and not hairs that when we triggered the movement of those hair cells they're going to signal hearing and the nerves coming out of the cochlea on our models on the back of the cochlea would be called the cochlear nerve and all the axons from all the hair cells in the cochlea are going to exit there and if you look at the model we had some little lines coming out of the ampule the utricle and saccule that are going to form a large nerve called the vestibular nerve i'm just going to abbreviate it but that would be our vestibular nerve going to what we call the vestibular complex the vestibular complex includes the vestibule and the three semicircular canals this the vestibule and the semicircular canals are or the vestibular complex are going to monitor equilibrium our sense of balance okay so now these two nerves are going to fuse together eventually and they're going to form what we call cranial nerve number eight the vestibulocochlear nerve okay sorry i didn't do that very well so our vestibulocochlear nerve or cranial nerve number eight is a fusion of the vestibular nerve and the cochlear nerve because the cochlea does hearing if i damage the cochlear nerve i lose my some of my sense of hearing if i damage the vestibular nerve or any of its branches i might lose some of my equilibrium there are some diseases which cause a sense of loss of equilibrium that damage the vestibular nerve or some of these structures in here okay anyway so now in your note set it talks about all of this and it talks about the semicircular canals i want to focus on them first and then we'll do the utricle and saccule so of the vestibular complex the three semicircular canals themselves monitor what we call rotational motion and this is the blank in your note set if you're following along on page 18 the three semicircular canals can detect rotational motions so those movements if we're spinning in one of three axes front to back side to side or actually what we call horizontal rotation and then lateral or side to side rotation so this is how it works if i were to cut this little area out here and magnify it then the membranous labyrinth comes down and it will bulge out into a structure inside the ampulla there's a group of neurons some cells that sit in here in a little bump like this and right on the edge here are some neurons they're going to have some little cilia or hairs sticking out it turns out that some of the fluid in the inner ear will gelatinize kind of like the vitreous body in the eyeball and that will sit on here like this we call this the cupula and the cupula is sort of a gelatinous mass almost like jello so imagine if i had jello sitting in the bottom of a glass of water if i start to wiggle the water enough the jello will start to wiggle with it since it's semi-solid if i start to wiggle this cupula then i will start to bend the hair cells that are suspended in it if i bend them one way it'll tell me that i'm rotating in one direction if i bend them the opposite direction it'll tell me i'm rotating in another direction so each of the three semicircular canals have a cupula inside the ampulla and this little bulb of hair cells here is called the crysta crystal means comb like you comb your hair and that's what it looks like with the little hair sticking out it's called the crista ampullaris so each of the ampule of the semicircular canals have a crystal ampullaris and a cupula if you start to rotate if you rotate one direction as the fluid moves this way it might pull the cupula with it and if the fluid starts moving in the opposite direction it'll push the cupula which tells you which direction you're rotating okay you need to know that anatomy now one of the things i want you to know is this now that we see that anatomy i'm going to erase some of this so that i can continue to write over here when it comes to the three semicircular canals i want you to know which one monitors which rotational motion the anterior semicircular canal does what we call anterior and posterior rotation because of the way that it's positioned in our heads if i lean my head forward or backwards those hairs get bent in opposite directions so if you were sitting in a tire rolling head over heels in one direction or the other you would be signaling the anterior um ampulla and you would be signaling the hair cells there sending a signal out the vestibular nerve to your brain that you're doing this your head banding at a metallica concert or something the lateral semicircular canal does what we call horizontal rotation this is going to confuse some people but pay attention you would be rotating with the horizon this way like you're spinning like a an ice skater or a ballerina sitting there spinning and finally the posterior semicircular canal is going to do what we call lateral rotation that's what confuses people but lateral rotation would mean from right side to left side so if you were kind of rocking back and forth or if you were doing cartwheels that would be the posterior semicircular canal okay so know that information now when it comes to the utricle and saccule within the vestibule the utricle and saccule are going to monitor what we call or detect what we call angular rotation in mathematics and geometry if we travel in a particular line we call that the angle or we think of it as linear like in a straight line but they monitor the utricle and saccule monitor what we call angular motions and or linear motions and they monitor gravitational motion so if you're looking in the note set this would be your first blink they monitor angular or linear movement as well as gravity gravitational motion straight up and down or straight forward straight back now when it comes to the structures inside the the utricle and saccule there's a little structure in there called the macula and what we have is sitting in here we have a little group of these neurons like this with little cilia on them those cilia or hairs and then these cells are going to send axons out like this these are neurons okay this would have been dendrites but they're modified these are the axons sitting on top of these cells in the macula there is another mass of gelatin sitting on top of that mass of gelatin are going to be some little crystal like stones the term lith means stone like lithography means writing in stone and so they call these otoliths oto means ear like an otoscope for looking in the ear so the otoliths are these little stones that are sitting or little crystals that are sitting on this gelatinous math mass and together they're called otoconia and the staticonia and you can look at some of that anatomy in the book but these little crystals are stones the otokoni or otoliths are sitting on this gelatinous mass and the hairs of the cells of the macula are sitting in there if we move in a straight line then those little otoliths can lag behind if i got shot forward if my fingers represent the hair cells and this represents one of those crystals if i move really rapidly in one direction or let me pick this up i'm sorry if i move really rapidly in the opposite direction it will lag behind and pull those hairs or those cilia if i pull them one way it'll tell me that i'm moving in an anterior direction if i pull them in the other way i tells me i'm moving in a posterior direction and the electrical and cycle are set up differently so that when i bend them it tells me if i'm moving up like if you got in an elevator or you got shot straight up in a ride on like on a um like one of the rides at a big theme park or if you got dropped you would feel yourself falling that gravitational motion up and down and straight forward and straight back it's handled by the utricle and saccule so all of this stuff is in the notes as a matter of fact i want to read this to you so that you can understand so it says they monitor angular or gravitational motions the utricle and saccule are clustered into small structures called macule plural and maculo would be singular the cells are sitting in a gelatinous mass and on top of that are a bunch of little structures called otoliths they make a mass called the oticonior staticonia and it's those movements so when you read those words in the note set hopefully these pictures help you understand that now i'm not going to make you learn which direction they go acceleration deceleration you can look that up if you like okay so that is all the information i want you to know about equilibrium i do want you to understand that the vestibular branch of the vestibulocochlear nerve it's going to monitor um our sense of equilibrium and if any of these structures get damaged we can get a sense of sort of a dizziness um so um or you know another term for that feeling of lack of of equilibrium is called vertigo that's the technical term for the dizziness or sort of that being off balance or lack of equilibrium also sometimes if people get punched or hit their head or just move too rapidly the fluids inside of here can displace some of those otoliths and then you can feel sort of a constant vertigo there's a move that was figured out by some physical therapist that if you do this real weird body positioning to move really fast sometimes you can rebalance them so some people get vertigo for that reason also when you get inner ear infections you feel a little dizzy or off kilter or if you have a sinus infection because the ear nose and throat are all connected we sometimes will hyper secrete these fluids putting pressure on these structures and you just feel a little woozy or lightheaded you have a slight case of vertigo when you're not feeling well when you're very stuffy all right listen i'm going to do one more video which is going to cover hearing so we'll be done with sensory physiology i hope this was helpful i hope you learned something i hope you had as much fun as i did all right see you guys on the flip side in the next video