To understand tinnitus better, what causes it, and what can be done to stop ringing ears, it helps to know something about our hearing and how it works. This third article in a three part series introduces the basic anatomy of the inner ear, what it does, how it can go wrong to give rise to tinnitus, and how it can be treated. The other two articles focus on the outer ear and the middle ear and tinnitus. With no further ado, let’s get a look at the inner ear.
Up to this point, we have traced the movement of sound waves through the air, then gathered by the pinna, funneled through the auditory canal, at the end of which the sound energy impacts the eardrum. The sound waves vibrate the tympanic membrane or ear drum, and the sound energy is passed on to the ossicles of the middle ear, the malleus, incus, and stapes. Those ossicles or tiny bones leverage the vibrations, amplifying and focusing the sound energy, which is then transferred to the cochlea of the inner ear.
Through the outer ear and middle ear the sound energy moves through air, which has much less inertia than liquid, but when the energy meets the inner ear, it encounters a fluid medium which has much greater inertia. Overcoming the greater inertia or resistance of the denser fluid medium of the inner ear is the reason for the amplification of the sound energy performed by the ossicles of the middle ear. And within the inner ear the sound goes onward to the brain in quite a different way.
The inner ear is commonly called the labyrinth because of the shape of the cochlea. The word cochlea literally means “snail” or “spiral shell,” and that is what it resembles. It is inside the cochlea where the mechanical vibrations are transduced or converted to electrical nerve impulses which the brain then processes as hearing.
When we get inside the cochlea, we find three fluid filled tubes. Two of them, the vestibular canal and the tympanic canal, transmit the pressure caused when the stapes of the middle ear presses against the oval window of the cochlea. The third canal, the cochlear duct, houses the sensitive organ of Corti which detects pressure impulses and responds by sending out electrical impulses which travel along the auditory nerve to the brain. Together, these three ducts curve into the snail shape of the cochlea. These canals are separated by a thin membrane called the basilar membrane.
The basilar membrane provides the base for the 20,000 or so tiny hair-like sensory cells. These hair cells respond to the sound energy moving through the inner ear creating the electrical impulses. Then, the organ of Corti which is situated on the basilar membrane, serving a microphone like function, sends those electrical impulses down the auditory nerve to the brain to be processed as recognizable sounds.
The way our inner ear enables us to hear is amazing enough by itself, but this incredible little component of the body is also command central for the body’s mechanism of balance. Certain other functions of the body also contribute to balance, such as the sense of sight and input from muscles, but the vestibular system of the inner ear is the centerpiece for maintaining balance.
The vestibular system has three essential parts: the utricle, the saccule, and the 3 semi-circular canals or ducts. The utricle and saccule constantly track the position of the head. Since the primary balance system for the body is located within the head, tracking the head’s position is very important. The utricle and saccule function by their sensitivity to gravity and acceleration. The utricle keeps track of horizontal movement, and the saccule keeps track of vertical movement. Working together, these two tiny organs keep track of head movement in all three dimensions, and keep the brain informed, and that helps us to keep our head aligned and our bodies in balance.
Yet another marvel is how these tiny organs work. Inside the utricle and saccule are minuscule particles of calcium carbonate floating in thick fluid. They are also lined with tiny hair-like receptors. Whenever the head is moved, the particles suspended in the fluid are also moved by gravity or acceleration and come in contact with the sensors which respond by sending signals to the brain for processing. The brain can then tell whether only the head is in motion or the whole body. Of course, the brain receives input from other sources, such as the eyes and muscles, but it is the vestibular system that is chiefly responsible for keeping the head and body balanced.
At the same time, the three semi-circular canals or ducts are serving much the same purpose as the utricle and saccule. However, rather than having the primary focus on head movement, they monitor the movement of the entire body. These three semi-circular ducts are called, superior, posterior, and external. In order to take into account all three spatial dimensions, these ducts are in perpendicular alignment to each other, so that any motion, forward or backward, left or right, up or down, or any combination of motions can be processed properly. The semi-circular ducts function in much the same manner as the utricle and saccule. The semi-circular ducts are fluid filled and have hair cells that are sensitive to gravity and acceleration, and respond to motion by sending electrical impulses along nerve fibers to the brain.
The tiny inner ear does all of that work, all of the time, whether we’re thinking about it or not. To maintain our sense of balance, we depend on the vestibular system to gather motion information and send it on to the brain. In turn, the brain interprets the data and makes sense of it all, sorting out all of the competing signals, and sending out its own information to the muscles, to keep us in balance at all times.
When balance and tinnitus ringing in ears both become problematic together, it’s often an indicator of Meniere’s Disease, which accounts for nearly one percent of all tinnitus cases. Yet, a much more common cause of tinnitus that develops within the inner ear is acoustic trauma that damages the sensitive hair cells of the cochlea, otherwise known as noise-induced hearing damage. Most noise-induced damage can be prevented easily by avoiding places where loud sounds are generated or by wearing ear protection in the form of ear muffs or ear plugs. For tinnitus due to acoustic trauma, the best tinnitus treatment can be found using a solid holistic process that will stop ringing ears.
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