Sense of hearing
Hearing is the second most complex sense. Vision is the most complex. The technical term is auditory sense. The auditory system is a little confusing because you have two physical systems in it: one for the auditory sense, and the other for the vestibular sense. The ear, the part that you are familiar with, the pinna, the outer part. You're probably meaning the pinna when you say ear. There are three divisions of the ear:
Outer: pinna, auditory canal,
Middle: ear drum, all of the bones that help it operate
Inner ear: cochlea, and other parts.
What's the function of the pinna? It directs the sound, and so people that have ears sticking out are able to have better hearing, so if your ears are flat against your head, you can't hear as well as those with sticking out ears. It also keeps out bugs and stuff. 80% of ear pain is related to bug inside of an ear. So all that stuff about ear aches and they go away? That's probably due to a creature that takes up residence in your ear.
There was recently a story about an eight year old who had two spiders living in his ear. He was complaining about ear aches, and they finally did surgery and flushed out two full grown spiders. Your ear drum is so sensitive that anything touching it will make you go crazy.
Eustacian tube- equalizes pressure in the middle ear.
Ear wax keeps all the nasty stuff out. It pushes dirt out of the ear canal. Don't ever use qutips. It's extremely easy to puncture your ear drum, and it's closer to the surface than you think. 75% of deafness afflicted by injury, well, that's due to qutips. You're pushing the wax further in, and it compounds against the ear drum, and that's not good. You're supposed to just wash the outside of the ear, etc. "Nothing bigger than your elbow inside your ear." Stop using qutips. You can clean the outside of your ear, however. The ear cones? Where they have wax in fabric tubes and they light the end, what does that do? It creates convection, it causes the warm air to travel to the end of the tube and warm up the inside of your ear canal, technically it's supposed to soften up the wax and so on, but there's also instances of where people pop their ear drums by putting it in their ear, so that's not good. Ear coning should not be done at home- do it at the doctor's office. Ear plugs also force wax back down the canal, or keeping water from going in, so the silicone earplugs are preferred, which seals the hole on the outside, instead of pushing things into it, and they seal better and don't go down the canal. That's the outer ear.
The ear drum and the ossicles. These are the three bones in the middle ear: the hammer (Milius), the anvil (incus), and the stirrup, and these serve to move the inner liquid within your ear. The cochlea is filled with fluid and that's where the actual sensation of hearing happens. The pinna, the auditory canal, the ear drum, hammer, anvil and stapes, and the cochlea, and then there's the eustacian tube, and there you have all of the major components. The eustacian tube, runs from the inside of your thought up into your ear, and that's what gets infected most frequently, so you can have an ear infection deep inside your ear. When you blow your nose too hard, you can feel a pressure shift in the air inside the eustacian tube, so when you fly, what happens? Your ears pop and you have to crack your jaw to pop, or you blow to pop, you're forcing air up inside the eustacian tube and forcing the airs to equilibriate, so when you're diving there's water in your ear, against the ear drum, it starts to build up and hurt, and so when you blow air up your eustacian tube, it tries to make equilibriate.
Ear shunt? In the membrane that holds the ear drum in place, they probably had something that makes the ear drain down the eustacian tube, and they create a channel for proper drainage to do, and sometimes they have to replace the shunt later when the kids grow up or take it out.
The eustacian tube helps keep equilibrium and pressure. It has some faults: it is the way to introduce bacteria to the ear. When you have to sneeze, sneeze or else you can force stuff up inside your ear and that's not good.
Tympanic membrane- a real, tight, very thin membrane that is sensitive to shifts in air. The way you hear, the sound waves (pressure) that travel down your auditory canal, causing the ear drum to move, and the ear drum responds to that pressure, and it starts to move the bones in the middle ear, and the first bone it moves is the hammer, and when the hammer moves, it moves against the anvil, and when it hits the anvil, the bottom part of the anvil moves, and then the stirrup pushes against the oval window. You've had sound waves (mechanical pressure) change the ear drum and cause mechanical shift in the bones of the inner ear which begin to cause pressure against the oval window. That's the two components of how you hear. The next step: air -> mechanics -> liquid, in order to hear. The stirrup starts moving, pushing against the oval window, which is an extension of the cochlea.
The cochlea is snail-shaped, swirls, made up of the basiller membrane and is filled with fluid. The cochlea has three chambers. The bassilir membrane makes all the folds in the cochlea. The way that you hear is this: that oval window is being pushed against this fluid system, and like a water balloon, it is having to respond, kind of like the movement of the liquid inside a water balloon, and this fluid tickles the hair cells- cilia. As these liquid waves move down the basiliar membrane, it moves the cilia, and as they are moving, they are tickling the Organ of Corti and that is the site of transduction in the ear. The organ of corti transduces hair cells from the liquid in the bassilar in the cochlea due to the cochlea from the oval window due to the ossicles which are in the ear drum which is stimulated by sound waves.
As the hair cell is waving, it is triggering the neuron, which transmits information. You kill cilia every day, and they never grow back. You are being constantly exposed to loud and sharp noises. To go back in time to where your grandfather and grandmother had their hearing tested, you would see that at your age they had much better hearing. Every time you listen to music that is loud enough to not hear the sounds around you, you're going deaf. Humans in the urban environment, due to football games, cars, etc., firedrills, etc. everything is so intense, and these intense bouts of sound, means that you are losing hair cells. Listening with earbuds, and trapping the sound inside the ear, that's killing more cells than before. You might listen to loud music, you have to judge when you really want loud music, don't have it all the time, just have it some of the time, and there's some other stuff - frequencies and so on. There are certain frequencies worse than others. Once the cells are dead, that's it, they do not regrow.
Noise pollution laws
-- So the cilia in your ears are screaming and dieing, THERE IS ONLY DEATH. There is a limited amount of audio information that you can consume within a lifetime because of these auditory limitations.
Neural pathway of sound: when you actually register sound, in the organ of corti, it gets translated to the vestibulo cochlear nerve. That means it serves both the vestibular system and the cochlea in the ear. Technically, after it registers in the organ of corti, the nerve impulse is sent from the vestibulo cochlear nerve to the medulla, then to the thalamus, at the brain stem, which then relies it out to the somatosensory cortex and the auditory cortex, primarily to the auditory cortex. Then you interpret it: what kind of sound is it, what do you need to do to respond, etc. So the first step: vestibulo cochlear nerve, medulla, thalamus, somatosensory cortex & auditory cortex.
They've been able to trace the audio path precisely, it's about 17 steps in totality.
How is frequency registered? When you register sound, the highest frequency is registered at the tip of the cochlea, so you hear high frequencies first, and low frequencies last, so you go deaf in high frequencies first, and then later on the low frequencies. There are various regions of the auditory cortex that perceive higher frequencies (at the higher areas). How do hearing aides work? They can either amplify sounds (like a little speaker), some hearing aides actually change frequency, bringing the pitch down, and then there's the cochlear implant- a transplant, in the cochlea, that you can use to translate the sound better, and so people that are completely deaf due to the cochlea can get an implant and begin to hear.
Cell phones and hearing aides are not good. Some have mechanical implants, a small computer chip / transistor radio.
Vestibular system
Gives you balance. Inside the inner ear. Part of the cochlea. It's part of the ear anatomy, but it's a whole different sense system. There's three semicircular canals, once that's horizontal, one that's vertical, one that's slanted, and it helps to figure out how the head is slanted or positioned. This is like the carpenter's leveler, except three-way, and the fluid moves in the canals. This is how you are able to know how your head is positioned. It goes through the same vestibular cochlear nerve. It's an extension of the cochlea. It's very simple. How can you mess this up? If you spin around, this will get messed up. Vertigo- swollen inner ear, and this causes the wrong cues due to pressure, etc. Flying with a sinus infection means that the intense pressure changes from the plane to your ear, it will quadruple your pain. It's like being on a ship, and you're unable to control your level. Spinning around will make the liquid spin as well in the vestibular, so if you spin the other way, that kind of helps.
Drinking alcohol effects your cerebellum, and then your vestibular system doesn't have any problems. Alcohol affects the cerebellum, which is where the control is, motor control and recognition and planning movements and so on. That's what the "trip" is all about.
Taste
How many tastes are there? There are five tastes- sweet, sour, salty, bitter, and umami. This is named after the Japanese scientist who discovered it. There are 10,000 taste buds. You have sensitivity to flavors in certain regions of the tongue. What's umami? It's actually a compound to detect whether you are a supertaster, and it's apparently a fifth flavor. A supertaster is a person who is extremely sensitive to taste, and they tend to have more taste buds than other people, and they are very accute. They've found that people who are supertasters, detect flavors more strongly and in more ranges. Most supertasters have an aversion to bitter, they do not like bitter forms, that's like brochlea and stuff. When you're looking at images? You're not necessarily detecting what's really there- it's the same with taste, you're tasting your perception of the food, so all food tastes different to people, but we for some reason tend to agree about generalizations or whatever. Supertasters like bland food. This guy, Umami, used this compound, and he found that people thought that Umami tastes like burnt rubber, and somebody who's not a supertaster, they will not taste umami at all. Umami did a taste test with supermodels, and took 20 of them, and found that they were all supertasters, and then he wondered about tall skinny people, and there seems to be a correlation between body size and how well you taste. If you are a supertaster, you seem to not eat as much because of the extreme taste. Men and women, sex wise, have a different experience of tastes. Women can detect sour and bitter, and men like stronger flavored, more skuny type food than women do. Poison is usually more bitter, so in an evo-devo-psych way, that's useful for women. Men also have an ability to manage more poisons and rotten foods.
Papillae- these are what you call taste buds, but that's not right. Papillae are the tasters. They are the bumps on the tongue. The taste buds are the tiny cells on the sides of the papillae. Taste and smell are chemical senses, so with taste, you need saliva or else you will not taste things very well, your saliva dissolves the molecules in whatever you ate, and that washes the fluid over the tongue and hits the papillae, seeps into the crevices, and that's where the information gets to the taste buds in the crevices.
The taste buds are the site of transduction. The poisonous blowfish, if you get poisoned, will shut off the bitter cells, and so the sweet ones are staying on, so you should hope that the chef knows how to remove the blowfish poison. It's an enzyme in the meat of the fish.
Primary gustatory fibers synapse centrally in the medulla (in a thin line of cells called the nucleus of the solitary tract). Tongue -> gustatory nerve -> medulla -> thalamus -> somatosensory cortex -> hypothalamus & amygdala. Your hypothalamus determines whether or not you are still hungry. The amgydala is for memory of whether or not you liked that food or to write into the memory that you do like the food. Have you ever tasted something and have a memory come back? Memory and smell work strongly together, as well as with taste. When you have a cold, stuffy nose, can you taste as much? Those two senses work hand in hand. If you flat out can't smell out at all, you only have the most basics of taste, like sour etc., you can't distinguish between lemons and lime. There's an experiment out there where if you get a subject, who plugs their nose, and give them a piece of onion, they will not know if it's onion, apple, or potato, because the texture is the same, and you have to be able to smell it, specifically apple and potato.
Gustatory fiber- bound to the taste buds, bound to the gustatory nerve.
The tongue goes to the tenth cranial nerve or something, and we have 12 cranial nerves, so that's the chances that this is right.