DIFFERENCES BETWEEN PERI AND ENDOLYMPH

1. Location:
   • Perilymph fills the bony labyrinth, which is the outer structure of the inner ear. It surrounds the inner structure, known as the membranous labyrinth.
   • Endolymph is inside the membranous labyrinth, which is a series of tubes and chambers within the bony labyrinth.
2. Composition:
   • Perilymph is similar in composition to the fluid found outside cells (extracellular fluid) and has high levels of sodium and low levels of potassium.
   • Endolymph, on the other hand, has a unique composition with high levels of potassium and low levels of sodium, making it similar to the fluid inside cells (intracellular fluid).
3. Function:
   • Perilymph acts as a cushion, protecting the delicate structures within the ear and helping to transmit sound waves to the cochlea.
   • Endolymph is crucial for the function of the sensory hair cells in the cochlea (for hearing) and the vestibular system (for balance). Changes in endolymph movement stimulate hair cells, which then send signals to the brain about sound or head position.

• Where is the organ of Corti located within the cochlea?
• What fluid is found in the cochlear duct?
• Entry of potassium into hair cells as stereocilia moves causes what to happen in the cells?
• Lower frequencies vibrate the basilar membrane closer to the apex of the cochlear whereas higher frequencies produce vibrations closer to the base. What is this known as?
• What nerve is responsible for transmission of sound to the brain?