The History of Your Ears Dates Back Millions of Years!
Research recently conducted by Dr. Kathleen Cullen at McGill University in Montreal has uncovered two very different sensory systems within our vestibular system. One of these systems was found to date back hundreds of millions of years – to before life ventured onto land. Before delving deeper into these two systems, it is important to understand what the vestibular system is, and how it works to help us in our daily lives.
What the vestibular system is, and why two systems are better than one
The vestibular system is located within our ears, and is our system of balance. The vestibular system helps us to orientate ourselves within our space. It’s what allows us to walk, skip or sit up without falling over. The vestibular system also allows us to see clearly while moving.
As Kathleen Cullen explains in the podcast, we use it to keep our gaze steady as we move through our environment. “If we didn’t have a vestibular system our eyes would bounce around like a GoPro, like you put a GoPro on your head,” she says. The vestibular system takes sensory input from our environment and triggers our eyes and head to make tiny and extremely precise opposite movements, to keep our sight steady and regular.
Scientists have known about the vestibular system for quite some time. What is notable about Dr. Cullen’s research is her discovery of two separate sensory systems or channels to transmit the information.
One channel dates back hundreds of millions of years, and is slow and smooth. The second channel is extremely quick and precise. This channel is thought to have evolved more recently – namely when organisms began venturing out onto land from the ocean. This makes sense, since movements on land are more complicated and require quicker and more attuned reactions, whereas slower and smoother movements occur in water.
During the podcast, a question was raised as to why we still have the older vestibular channel. Cullen believes that for slower and larger movements, such as moving your head side to side when saying no, the ancient system is more accurate, and still necessary for our functioning. To listen to the full podcast, click here.
Of course, hearing is also an extremely important function of our ears!
How hearing works
Remarkably, the human ear is fully developed at birth. Even in utero, infants respond to sounds. Although fully developed at birth, the sense of hearing is relatively complicated. The full hearing process can be divided into four steps.
1. First, sound enters the ear, travels down the canal and strikes the eardrum, causing it to vibrate.
2. Then, sound travels through the middle ear. In the middle ear, there are three tiny bones called the ossicles. These tiny bones are connected to the eardrum at one end, and the opening of the inner ear at the other. When the eardrum vibrates, it causes the ossicles to vibrate as well.
3. Next, the movement of fluid in the inner ear (cochlea) begins to move based on the vibrations of the ossicles. The movement of the fluid in the cochlea causes delicate cells (called hair cells) to change and react.
4. Lastly, the changes in the hair cells send electric signals up through the auditory nerve and into the brain. It is at this point that our brain interprets the signals into sounds we recognize, thusly, allowing us to “hear”.
Our sense of hearing is quite fascinating, considering this entire process occurs in milliseconds.
What happens when hearing loss occurs?
There are two main types of hearing loss. The first and most common is sensorineural hearing loss. This type of hearing loss occurs when our delicate inner ear hair cells or the auditory nerve become damaged. Sensorineural hearing loss is usually permanent and can be caused by simply getting older, hereditary, illness, trauma, certain medications, and/or excess exposure to loud noise. Auditory nerves and inner ear hair cells don’t have the ability to regenerate themselves – once they’re gone (or damaged) – they’re gone for good.