The Cochlea and Scala Media

The cochlea is a spiral-shaped structure in the inner ear that plays an important role in hearing. It is filled with fluid and contains hair cells that are responsible for converting sound waves into electrical signals that can be transmitted to the brain.

One of the three main compartments of the cochlea is called the scala media (also known as the cochlear duct). This is the central compartment of the cochlea, located between the scala vestibuli (upper chamber) and the scala tympani (lower chamber).

The fluid that fills the scala media is called endolymph. This fluid is unique in composition and plays an important role in the function of the cochlea.

Properties of Endolymph

Endolymph is a fluid that is rich in potassium ions and has a positive electrical charge. This is in contrast to the fluid in the scala vestibuli and scala tympani, which is high in sodium ions and has a negative electrical charge.

This difference in ion composition creates an electrical potential difference across the hair cells in the cochlea. When sound waves enter the cochlea, they cause the hair cells to move and bend. This movement triggers the release of neurotransmitters, which sends electrical signals to the brain via the auditory nerve.

Importance of Endolymph

The unique properties of endolymph are critical for the proper function of the cochlea. If the composition of endolymph is disrupted, it can result in hearing loss and balance problems.

For example, a condition called Ménière's disease is characterized by an excess of endolymph in the inner ear. This can lead to symptoms such as hearing loss, tinnitus (ringing in the ears), and vertigo (a spinning sensation).

Conclusion

In summary, the space within the cochlea called the scala media is filled with endolymph. This fluid is critical for the proper function of the cochlea and plays an important role in converting sound waves into electrical signals that can be transmitted to the brain.