Hey! It's been a long time since I picked your brain. Lemme ask you a simple yet fascinating question- What is Sound? The scientific answer to the question is that sound is nothing but vibrations in the air molecules which get picked up by our ears and then get converted into something that makes sense, but how our ears take those vibrations in and then convert them into information is the spicy part! Today, in this blog I am going to answer a lot of mind intriguing questions such as Why do you get dizzy in a rollercoaster or what happens when you wear earphones for too long. Let's start!
Hearing & Balance- They are Interconnected!
As you might know, we have 5 sense organs- Ear, Nose, Eyes, Skin and Tongue. They are known as "Sense" organs because they help us sense the world around us. Today, we are going to be focusing on one of them which helps us hear! You got it- Ears.
You might not know this but our ears play a great role in maintaining the Equilibrium of the body which is basically how the body can tell which way is up and which is down. It might sound like a simple thing but it is important. We will get back to this later and first understand the anatomy of the ears and how they help us hear.
Ear Anatomy- The reason I respect ENT's
Seriously, you have to give respect to ENT's (Ear, Nose and Throat Doctors). They understand the most complicated anatomy in all our body, which is of the ears and throat. Let's try and understand how the ears are structured.
The Ear is divided into 3 parts- The External, Middle and Inner Ear.
1. External Ear- It consists of the Pinna or auricle which is the the part of the which is all soft because of elastic cartilage and the only part which you can grab or wiggle around. It catches the sound waves and passes them along into the Inner ear.
The sound waves then travel through the auditory canal or the External Acoustic Meatus-that's a mouthful.
The sound waves then hit the Tympanic Membrane, also known as the Eardrum. This part is thought of as the most important part of the ear by a lot of people, but its not. The only function it has is to vibrate and pass the vibrations of the sound waves into the middle ear.
That was all about the External Ear, now let's get down to the nitty gritty of the Middle Ear.
2. Middle Ear (Tympanic Cavity)- It consists of 3 tiny bones which are the smallest of all the bones in the human body- The Malleus, Incus and Stapes- commonly known as the Hammer, Anvil and Stirrup.
The main job of these bones is to pass the vibrations along and also amplify them because that is important. Why you ask? Because the inner ear contains a special fluid and if you know anything about physics- Sound moves slower in a liquid as its harder to move in a liquid which you would know if you've ever gone swimming. The bones focus the pressure of the sound waves so they are strong enough to move through the liquid.
The Inner Ear is the reason I truly feel bad for medical students because that is where things get complicated but also a little interesting.
3. Inner Ear (The Labyrinth)- You're probably wondering why the inner ear is known as the Labyrinth and that's because it has some of the most complicated anatomy in the entire body. For reference, labyrinth refers to a maze because the inner ear is one.
The inner ear consists of the Bony Labyrinth, which is the rigid outer structure made up of bones and the Membranous Labyrinth which is inside the Bony Labyrinth and follows its shape.
The Membranous Labyrinth is the one which is filled with fluids which circulate the ear and are secreted by the pseudostratified epithelium in the cochlea known as the Stria Vascularis.
The cochlea is a snail-shaped structure in the inner ear which is the main organ helping us in hearing. If you cut the cochlea into little cross sections, you will notice that each section contains 3 chambers known as the:
1. Scala Vestibuli
2. Scala Media
3. Scala Tympani
The Scala Vestibuli and Scala Media are separated by a membrane known as the Reissner's Membrane. It is bathed in a special type of fluid known as the Perilymph which helps transmit sound wave and it helps keep the 2 chambers separate.
The Scala Media and Scala Tympani are separated by a membrane known as the Basilar Membrane.
It is also bathed in a special type of fluid known as the Endolymph which is secreted by the Scala media (Stria Vascularis).
How do you hear sound?
The Basilar Membrane contains vibrating fibres which are short at the base and long at the apex. Their height decreases from top to bottom. These fibres vibrate when sound waves hit them, but there is a catch! The fibres at the bottom (the short ones) can only vibrate when high frequency sounds hit them.
The fibres at the apex (the long ones) can only vibrate when sounds of low frequency hits them. That means that whatever you hear comes down to what tiny section of the membrane is vibrating.
Now, another important part of the cochlea known as the Organ of Corti sits at the top of the Basilar membrane. It contains sensory cells known as Hair Cells which are not real hair cells, they are just called that because they contain tiny-hair like projections known as Stereocilia, which despite its name is not cilia but is actually made up of the actin filament found in muscles. Its called cilia because it looks like them.
These hair cells in the Organ of Corti vibrate as a result of the vibrating fibres inside the Basilar Membrane and interact with the Tectorial Membrane. The stereoclilia as a result of the interaction get bent which open voltage gated potassium channels and potassium ions rush in to trigger an action potential leading to depolarization.
The electrical impulse travels through the 8th Cranial Nerve- The Vestibulocochlear or the Auditory Nerve. It reaches the auditory cortex in the temporal lobe where the brain makes sense of the signal based on the vibration of those fibres and that is how you hear sound.
Now that we got the hard part down, let's talk about how your ears maintain equilibrium in the body.
Maintaining Equilibrium- An important job indeed!
The Inner ear uses another part to maintain equilibrium in our body and that part is called the Vestibular Apparatus and not to joke, it looks like some kind of alien body part.
This organ also uses a setup of fluid and sensory hair cells but this time, they vibrate and send signals to the brain because of the movement of your head.
The Vestibular Apparatus contains 3 semicircular canals which contain fluids which sense the motion of the head because of the fluid moving in the ear.
These fluids detect motions such as tilting, side to side and up and down respectively. Each semicircular canal widens at the base into 2 sac-like structures known as the Utricle and Saccule.
The Utricle and Saccule contain sensory hair cells which detect the movement of the fluid in the semicircular canals and send action potentials to the brain based on the movement of the hair cells. The brain detects these signals the same way it does with hearing- based upon which hair cell is vibrating and where. For example- If I bob my head up and down, the fluid in the semicircular canals will move up and down and the hair cells will detect that and send the information to the brain through the Acoustic Nerve (a branch of the auditory nerve).
Motion Sickness
Motion sickness is described as a recognised disorder where people have certain symptoms such as Nausea, Dizziness, Headaches etc while in moving vehicles or anything which moves fast such as a rollercoaster ride. There have been some extreme cases in which rocking chairs caused people to have motion sickness.
Why it happens is pretty simple. Imagine you're on a speeding boat, now your eyes see just the water, they don't really perceive anything moving but the fluid in your ears is telling your brain that your head is moving forward and backward. This creates a Sensory Conflict and confuses the brain leading to symptoms of motion sickness.
Only some people have motion sickness because their brains might be more sensitive to it or they could be having stress or it could be genetic.
The Eternal Conflict- Are Earbuds or Q-tips bad for you?
Yes, they are! But hear me out, Ear Wax or Cerumen (called cerumen because it is secreted by the Ceruminous glands which are modified apocrine glands meaning they secrete their substances in hair follicles, apocrine glands are type of exocrine gland), is not dirt. It traps bacteria, dust particles, and it provides moisture to the ear. Using earbuds can push it further into the auditory canal, leading to blockages, hearing discomfort or Eardrum rupture. What you can do to clean your ears is use a piece of cotton and a cream or just a wet cotton to clean the outer ear gently.
Its not a sign that your ears are dirty but rather a sign that they are cleaning themselves. If you have a feeling that this might be false information, feel free to speak to your healthcare provider. You can also clean your ears using soap in the shower but again don't go too deep inside.
Is wearing earphones for long periods of time bad for you?
Yes, because of the following reasons:
•The stereocilia can get damaged due to listening to loud volume for long periods of time. This damage is irreversible.
•Tinnitus (ear ringing) or a constant buzzing sound can develop.
•Just like earbuds or Q-tips, earphones can push the earwax inside leading to blockages, discomfort etc.
•They can trap moisture leading to bacterial or fungal infections.
Final Verdict: Take care of your ears and respect Otorhinolaryngologists (ENT's)
Fun Fact
Let's talk about some medical terminology as I started that in the last blog. It will help clear things up. Oto- means Ear, Rhino- means Nose and Laryn- means Throat (from Larynx), Ologist- means a specialization. So, that's why ENT's are called Otorhinolaryngologist.
That's it for this blog, I enjoyed it and you all got to learn something, see you next time!
P.S.- This blog had a lot of medical terminology which if you haven't read my earlier blogs, you won't be familiar with, so I will give a reference to my other blogs in the below section.
References- The Foundation of Human Anatomy: Tissues Part 1 and Part 2, The Nervous System and The Brain, Anatomy 101: Directional Language and Skeletal System, The Endocrine System: The Body's Chemical Messangers.
You can visit the further blogs at this website: deeparshbhanot.blogspot.com
Regards,
Deeparsh Bhanot
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