The inner ear
What is the inner ear?
The inner ear is the innermost part of the ear. The parts of the inner ear are the cochlea, the balance mechanism, the vestibular and the auditory nerve.
How does the inner ear function?
Once the vibrations of the eardrum have been transmitted to the oval window, the sound waves continue their journey into the internal ear. The parts of the inner ear have very important purposes for your hearing and your balance.
The inner ear is a maze of tubes and passages, referred to as the labyrinth. The vestibular system and the cochlea are located in this labyrinth.
The cochlea: function and anatomy
The cochlea has a very important function in the hearing process: In the cochlea, It transforms sound waves into electrical impulses which are sent on to the brain. The brain then translates the impulses into sounds that we know and understand.
But what exactly is the cochlea and how does it work? The cochlea resembles a snail shell or a wound-up hose and is filled with a fluid called perilymph and contains two closely positioned membranes. These membranes form a type of partition wall in the cochlea. However, in order for the fluid to move freely in the cochlea from one side of the partition wall to the other, the wall has a little hole in it (the helicotrema). This hole is necessary, in ensuring that the vibrations from the oval window are transmitted to all the fluid in the cochlea.
When the fluid moves inside the cochlea, thousands of microscopic hair fibres inside the partition wall are put into motion. There are approximately 24,000 of these hair fibres, arranged in four long rows.
The auditory nerve: function and anatomy
What is the auditory nerve? The auditory nerve is a bundle of nerve fibres that carry information between the cochlea in the inner ear and the brain. The function of the auditory nerve is to transmit signals from the internal ear to the brain.
The hair fibres in the cochlea are all connected to the auditory nerve and, depending on the nature of the movements in the cochlear fluid, different hair fibres are put into motion.
When the hair fibres move, they send electrical signals to the auditory nerve which is connected to the auditory centre of the brain. In the brain the electrical impulses are translated into sounds which we recognise and understand. As a consequence, these hair fibres are essential to our hearing ability. Should these hair fibres become damaged, then our hearing ability will deteriorate.
The vestibular system – the balance mechanism
What is the vestibular system? The vestibular system is another important part of the inner ear. The vestibular system is the organ of equilibrium. The vestibular system’s function is to register the body's movements, thus ensuring that we can keep our balance.
The vestibular system consists of three ring-shaped passages, oriented in three different planes. All three passages are filled with fluid that moves in accordance with the body's movements. In addition to the fluid, these passages also contain thousands of hair fibres which react to the movement of the fluid sending little impulses to the brain. The brain then decodes these impulses which are used to help the body keep its balance.
Disorders of the vestibular or infections in the inner ear can cause vertigo, the spinning sensation of dizziness.
The inner ear is only a part of the fascinating apparatus that enables us to hear and maintain our balance. Continue learning more facts about the ear, facts about the middle ear and understand the functions and parts of the outer ear.