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Hair Cells: Types and Functions

Friday, May 17, 2019 11:08:44 AM Asia/Calcutta

Hearing is a very complex procedure and involves a series of steps in between the origination of the sound source and our brain’s interpretation of it as a particular type of sound. Although this whole process is as quick as a fraction of a second, the journey of sound is quite complicated, just like any other mechanism in the human body.

You will be surprised to know that the human ear is quite well-developed at birth and even at the pre-natal stage. This explains why babies respond to sounds while in their mother’s womb. Every baby with normal and healthy hearing has the ability to hear and respond to soft and loud sounds right away. However, if your baby fails to do so, then it might be a sign that you need to be high on alert. Do consider getting your child’s hearing test done right away. If your baby is diagnosed with a hearing impairment then do consider opting for a good line of hearing loss treatment by consulting a licensed and professional Audiologist at every major or minor step that you take. Nowadays, however, every hospital performs a hearing screening of newborn babies right after birth and before you take him or her home.

One very important part of hearing are the sensory cells present inside the cochlea of the inner ear - known as the hair cells. But before we get deep into that, let’s take a brief look at the hearing mechanism once more to simplify our understanding of the hair cells. Because just like the structure and arrangement of these tiny cells, their functioning too is quite complex and requires a deeper understanding of the entire scenario.


The Hearing Mechanism

As already mentioned, the human hearing mechanism is a complex one. It involves a good number of phases, it also associates a number of elements and sections of the ear. So let’s see how do we actually hear.


The Sections of the Ear

There are three main parts of the human ear -

  • The Outer Ear - It includes the pinna, the long passage called the ear canal and the tympanic membrane, better known as the eardrum.

  • The Middle Ear - It comprises the three small ear bones - incus, malleus and stapes - together known as the ear ossicles.

  • The Inner Ear - The inner ear, which is the main component of the human hearing system, is also known as the labyrinth of the ear. Now that we know that it is solely responsible for our hearing system and the equilibrium of the body, we will head over to discuss the hair cells present inside the cochlea.

It comprises the most vital and sensitive organ - the spiral-shaped cochlea. The inner ear also includes two other important components, namely the vestibule and the semicircular canals - which together are responsible for maintaining the body balance and the body posture, thus preventing us from falling.


How Does the Hearing Mechanism work?

Let's break down the hearing process into simpler steps for better understanding.

  1. Sound waves enter the ear canal and strike the eardrum and make it vibrate.

  2. This vibration is then carried forward to the small ear bones or the ear ossicles.

  3. The middle ear bones amplify these sounds and send them to the cochlea of the inner ear. These vibrating waves move through the fluid present in the cochlea, thus making it move.

  4. This movement of the fluid further triggers the hair cells which are present inside the cochlea and causes them to move. These hair cells detect this movement and convert these signals into electrical signals for the auditory nerve.

  5. The auditory nerve then sends these converted electrical impulses to the brain which then interprets them as sounds. It is at this time that we actually ‘hear’.

But how well would these sounds travel from the outer ear to the inner ear and how well would these sounds be perceived by the brain depends a lot on how well your ears work. In case of any malfunctioning or disorders in your ears, you may face difficulties in hearing. In such a case, do consider getting a proper hearing loss treatment.


What are Hair Cells?

In all vertebrates, hair cells are sensory receptors which are not only present in the cochlea of the inner ear but are also present in the vestibular system. In this blog, however, we are concerned about the cochlear hair cells.

In mammals, the hair cells are located in the spiral organ of Corti on the basilar membrane of the cochlea. The cochlea has thousands of such tiny hair cells (we will get into the figures in the next section).


The Structure of the Hair Cells

Each hair cell has two parts - the body and the stereocilia present at the head of every hair cell. Stereocilia is a microscopic hair-like structure sticking out on top of every hair cell. These stereocilia are triggered by every sound vibration due to which they rock back and forth.

Stereocilia are the main components of hair cells. These are responsible for converting the sound waves into chemical signals. Whenever the hair cells move due to the cochlear fluid movement, the stereocilia bend. This bending causes the pore-like channels present at the tip of the stereocilia, to open up. This further facilitates the chemicals to rush into these hair cells, thus building up an electrical signal. These electrical impulses are then sent to the brain for further interpretation and perception of the sound. Then we recognise the sound and understand it, and immediately know how to respond to it.

Not all hair cells, however, move at the same time. Different hair cells move for different types of sounds. Hair cells located near the wide end of the cochlea detect higher-pitched sounds, such as an infant crying. Those closer to the centre of the cochlea detect lower-pitched sounds, such as the barking of a large dog. The high-frequency hair cells get damaged most easily, and hence people with hearing loss due to exposure to loud sounds often have problems hearing the high pitched sounds like crickets or birds chirping.


What Happens If These Hair Cells Get Damaged?

If the sounds are excessively loud, these stereocilia would bent or even break off, thus causing the death of the hair cell. A dead hair cell can never convert nor send signals to the brain, thus reducing your ability to hear well. The hair cells once broken can never grow back or be restored, and you would lose your hearing permanently in such a case. The more the number of damaged hair cells, the greater will be the intensity and degree of your hearing loss. This type of hearing impairment is known as a sensorineural hearing loss, and in such a case the best line of hearing loss treatment would be hearing aids, cochlear implants, assistive listening devices or other ear implants. Damaged hair cells might also cause tinnitus or ringing in the ears. If you are the one suffering from such a condition, do consult a skilled and professional Audiologist.


Types of Hair Cells

Now that we know that the primary function of the hair cells is to convert the analogue sound waves into electrical impulses so that these signals can be easily interpreted by our brain, let’s go deeper and discuss about the different types of hair cells.

In mammals. the hair cells of the cochlea can be anatomically and functionally classified into two distinct types - the inner hair cells (IHC) and the outer hair cells (OHC). In the human cochlea, there are 3,500 inner hair cells and 12,000 outer hair cells at birth.

The outer hair cells amplify the low-level sounds that enter the cochlea. The inner hair cells convert the sound vibrations travelling in the cochlear fluid into electrical signals. These vibrations are then relayed to the auditory nerve.

Damage to any of these hair cells leads to deteriorating hearing sensitivity.


The Difference Between the Inner and the Outer Hair Cells of the Human Cochlea


Inner Hair Cells

                          Outer Hair Cells

These are the main receptive cells which convert sound waves into nerve signals.

These hair cells pre-amplify the sound waves having a low amplitude.

These are 3,500 in number.

These are 12,000 in number.

These are arranged in a single row.

These are arranged in 3 rows.

These are located at the terminals of the inner hair cells.

These are located at the terminals of the outer hair cell nerves.

These are innervated by more afferent nerves than efferent nerves.

These are innervated by more efferent nerves than afferent nerves.

These have a cylindrical shape.

These are flask-shaped.


In a nutshell, take care of your hair cells by taking care of your ears. Protect your ears from any exposure to extremely loud sounds. Use earplugs when you are attending some loud events such as a rock show. Prevention is better than getting your ears damaged permanently and having no other option left than to go for a hearing loss treatment.

Also, make it a habit to get your hearing tested from time to time so that if you are suffering from any hearing problems (which you may not realise normally) can be diagnosed on time, and hence go for a proper hearing loss treatment on time. Hearing is a precious asset and a good hearing health paves way for a better quality of life.

Are you aware of any other facts about hair cells and their functions?

Do tell us in the comments below.

Sleep disturbances have affected almost most of us at some stage in our lives. Although insomnia prevalently affects mostly the older adults, it is seen in children as well. While some might have faced it for some mild or moderate reasons or health conditions, some suffer from insomnia due to serious reasons. The worst part is when it has become a regular aspect! According to a study, 54% of the people who have tinnitus problems, also have significant sleep disturbances.

But what if your sleeping disturbances are due to hearing problems like an impaired hearing or tinnitus? People with tinnitus might have greater difficulty in getting a proper night’s sleep. Obviously, there are a host of exercises that would help you out in getting better sleep, but the first and foremost step would be to get your ears checked for any hearing problems, and if any, start its treatment at the earliest - be it a treatment for your tinnitus problems or a hearing loss treatment, or even both.

But how would you know whether your sleeping disturbance is serious enough?


Insomnia vs. Mild Sleeping Disturbances

Insomnia is a condition in which a person has difficulty falling asleep and/or staying asleep. Do not get confused with mild sleeping disturbances, because insomnia is something much more serious. To be classified as insomnia, a lot of aspects needs to be taken into consideration such as the delay in going to sleep or going back to sleep. If your sleeping disturbances occur at least three to four times in a week and persist for six months or more, then you are most probably suffering from insomnia.


What is Tinnitus?

Tinnitus is the perception of abnormal sounds in the ears when there is no external sound present. While ringing is the most common tinnitus sound, other sounds include buzzing, hissing, clicking, humming and roaring.

In our previous blogs, ‘I Can Hear Ringing Sounds - Do I Have Tinnitus?’ and ‘How to Beat Tinnitus?’ you have seen what tinnitus is and what are the types of sounds one gets to hear in such a condition.


What are the Causes of Tinnitus?

There can be many causes of tinnitus, such as -

  • Exposure to loud noises

  • Ear infections

  • Injuries in the ear, neck or head

  • Hearing loss (though not every case of tinnitus is due to hearing issues)

  • Earwax buildup

  • Hormonal imbalances

  • Cardiovascular diseases

  • Thyroid disorders

  • Certain medications and drugs including antibiotics, antidepressants, cancer medicines and very high doses of aspirin

Tinnitus can affect different people in different ways. While some experience constant buzzing while others might hear only sporadic buzzing, hissing or whistling sounds.


How Does Tinnitus Affect Sleep?

It’s quite obvious that if you hear disturbing and often frustrating sounds almost all the time, you are bound to experience some kind of sleep disturbances. While in the daytime, you remain busy in some activities, thus being able to forget about your tinnitus sounds at least for some moment. But when you are back at home and are sitting in some quiet room with very minimal or no background sounds, or while you are in your bed, trying to sleep, the tinnitus sounds becomes all the more noticeable and frustrating. This contrasting situation between a quiet room and a continuous series of buzzing sounds in the ears are bound to make the condition more disturbing than usual.

Due to tinnitus you also feel very tired and fatigued even during the day. The worst part is, all these situations might gradually lead to stress and anxiety, thus making it difficult for you to fall asleep. So if this situation sounds like you, then the first thing you must aim at is to try and get a sound sleep each night - because proper rest is what you need at the end of the day - no matter what your health conditions are.

There may be several sleeping problems associated with tinnitus, including -

  • Having trouble falling asleep or staying asleep

  • Not getting enough sleep

  • Waking up frequently in sleep

  • Experiencing poor quality sleep

  • Not feeling refreshed in the morning

  • Feeling fatigued and tired throughout the day as a result


How to Sleep Better With Tinnitus?

There are some proven techniques that would help you have a better sleep if you are suffering from tinnitus. Here are some of them -

  • Avoid a too quiet bedroom - It would make you more conscious about your tinnitus problems and thus make you unable to sleep.

  • Use white noise to mask your tinnitus sounds - Tune in to a low volume and soothing background music that would help you to relax and sleep better. This noise suppression technique is quite effective and is recommended by Audiologists worldwide.

Certain devices which are helpful in masking tinnitus sounds include -

    • White noise machines - These devices produce stimulated environmental sounds such as the rushing waterfalls, the rustling of the leaves, pitter-patter of the rain, the ocean waves and other such nature-like sounds. These act as a calming effect on your mind by masking the tinnitus sounds.
    • Hearing aids - Certain hearing aids come with noise masking or noise suppressing features which can be quite helpful if you have both hearing loss as well as tinnitus.
    • Masking devices - These are worn in the ear and are similar to hearing aids. These devices produce a continuous, low-level noise which helps to suppress the symptoms of tinnitus.
    • Tinnitus retraining - Tinnitus retraining is a habituation therapy designed to provide relief to people suffering from tinnitus. Using tinnitus masking devices over time can help you get accustomed to these sounds so that you can shift your focus to something else. This technique is a type of counselling which is an essential component of tinnitus retraining.
  • Improve blood flow to your head - This means you need to exercise. For example, jogging, swimming, cycling, running, or yoga would be quite beneficial to you.

  • Practice mindfulness meditation - It involves sitting quietly and paying attention to your natural breathing. The idea is to distract yourself from those irritating tinnitus sounds as this meditation helps you to stop worrying about how you would sleep, work or stay focussed and the like. Start with a 5-minute session and as you would start growing comfortable with it, you may increase the timing. The best part is, you can practice mindfulness meditation anytime and anywhere!

  • Use other relaxation techniques - like deep breathing, aromatherapy, etc. aromatherapy is a process by which natural elements like plant materials and aromatic plant oils, including essential oils, and other aroma compounds, are used to improve the psychological or the physical well-being of a person.

  • Seek out cognitive-behavioural therapy - It is effective for reframing and eradicating negative thoughts, emotions and behaviours. It helps manage with stress, anxiety disorders and depression. Cognitive-behavioural therapy or CBT is also highly effective in treating insomnia and other sleep disorders.

  • Limit the use of earplugs - it will soften down external sounds, thus making tinnitus more noticeable. Also, using earplugs for longer periods of time can cause earwax buildup - which can further cause tinnitus problems.

  • Don’t ignore ear pain - Pain or discomfort in your ears can be the signs of tinnitus. Consult your Audiologist immediately whenever you face an ear pain.

  • Treat your hearing problems on time - Seeking hearing loss treatment at the earliest will help reduce tinnitus problems. Also, as already mentioned, there are some advanced digital hearing aids which are designed to provide relief to these annoying tinnitus sounds.

  • Treating an underlying health condition can help! Often, there are certain health conditions which are associated with tinnitus. Consult an Audiologist and get to know the reason behind your tinnitus and accordingly do consider treating that before anything else. For example, removing your hardened earwax or treating a blood vessel condition, or even changing your medication can help with tinnitus relief.

You will find great information about the possible treatments of tinnitus in the following link. Do check it out:

Tinnitus is the cry of dying ears! Seek immediate help, and if hearing loss is the underlying cause, go for a proper hearing loss treatment.

What do you think?

Are there any other techniques to help reduce tinnitus?

Are you aware of any technological devices which are very good for tinnitus relief?

According to the new researches, are there any chances to get permanent relief from tinnitus?

We would love to know! Do share your valuable opinions and feedback in the comment section down below.

Does Hearing Loss Cause Anxiety?

Monday, March 11, 2019 12:22:46 PM Asia/Calcutta

Did you often feel neglected because you were unable to participate in group discussions? Are you often being mocked at because you fail to respond at the right time or maybe because you said something which is already being told in the conversation? Did you feel that people are misunderstanding you because you are not able to understand what they are trying to convey and hence responding inappropriately? And after facing all these issues, did you feel that you should avoid all these situations and hence you start avoiding social gatherings?

All these might be the red flags that you are having hearing loss!

Read on to know more about How Anxiety is related to Hearing loss?

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Why is Cochlear Implant Suitable for Children?

Monday, January 14, 2019 1:49:25 PM Asia/Calcutta

You have so many dreams with your newborn child! You want to see him or her reach the heights, or even go beyond the limits and emerge victorious! But amongst these dreams, did you ever take some valuable time to ponder over and think about the present? Are you even sure that your child is having the basic requirements - such as that of a well and proper hearing health?

Yes you might think that your child is hearing properly, but there is no harm in making it 100% sure, is there? Do read our blog to find out why you need to get your child's hearing test done, and why you need to start a hearing loss treatment early, in case your child is diagnosed with a hearing loss. Don't let your dreams shatter and let your child dream as well!

Read More

Teleaudiology: Its Benefits and Strategies

Wednesday, December 19, 2018 3:37:07 PM Asia/Calcutta

Just imagine a situation in which you suddenly face hearing problems, and you are unable to find any Audiologist or a hearing loss treatment clinic near you, and you are in need of an urgent help and support! What will you do? Whom will you reach out to?

Or maybe the device right in your hand can help you out! Yes! Your mobile phone can save you! That’s called Teleaudiology!

So why not embrace the benefits of teleaudiology when it’s going to solve your hearing problems right away?!

Read More
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