A look at your inner ear

inner-ear

The inner ear is the delicate structure that transforms the sound vibrations from the stapes into nerve signals that are transmitted to the brain. It also plays an important role in maintaining our balance. The inner ear consists of tiny fluid-filled canals encased in some of the hardest bone in the body.

The hearing portion of the inner ear is called the cochlea, a snail-shaped structure connected to the stapes. As the stapes moves in and out, it produces fluid waves within the cochlea.

These waves in turn cause movement of tiny cells within the cochlea called the hair cells. As these hair cells vibrate, they send complex signals to the brain that are then interpreted as sound.

Other parts of the inner ear are responsible for helping maintain balance. The three semicircular canals are oriented at right angles to each other.

When we turn our head, the relative movement of fluid in these canals lets our brain know which way and how much we are turning. Another part of the inner ear responds to the gravitational force and lets our brain know the static position of our head.

The cells of the inner ear are exquisitely sensitive to injury from, for example, a virus infection or blood loss. Unfortunately, the loss is often permanent and does not correct itself.

Depending on the cells involved and the type of loss, this can produce hearing loss, tinnitus (ringing or other noises in the ears), or balance problems. The hair cells also tend to degenerate as we get older, often causing a high frequency loss.

'Nerve deafness'

Sensori-neural hearing loss typically occurs when part of the inner ear (consisting of the cochlea, hair cells and hearing nerve) is damaged or destroyed.

Also known as ‘nerve deafness’, may have a variety of causes, such as heredity, aging, disease, infection or sustained exposure to loud noise – the first image shows ‘normal’ hair cells and the second image shows the effect of noise damage.

normal-hair-cells damaged-hair-cells

Despite the term “nerve deafness,” the hearing nerve itself is rarely damaged. Instead, damage most often occurs in the hair cells located in the cochlea, which serve to send sound information (electrical signals) to the hearing nerve.

When hair cells are damaged, they are unable to send sound information to the hearing nerve and the person experiences hearing loss.