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Tympanic Reflex

  1. When the middle ear muscles (tensor tympani and stapedius) contract, they pull the manubrium of the malleus inward and the footplate of the stapes outward. Loud sounds initiate a reflex contraction of these muscles called the tympanic reflex. Its function is protective the reaction time for the reflex is 40 to 160 ms.


  1. Inner ear (Labyrinth) – the inner ear is designed in the form of a tube (membranous labyrinth) encased in a bony tube (the bony labyrinth). There is endolymph within the membranous labyrnith and perilymph surrounding the membranous labyrinth. There is no communication between endo and perilymph. 3 parts of the bony labyrinth house (contain) 3 parts of the membranous labyrinth;
Bony labyrinth Membranous labyrinth
Bony cochlea Membranous cochlea (also called cochlear duct, scala media)
Vestibule Saccule, utricle
Semicircular canals Semicircular ducts
  1. Cochlea- Its length in 35mm. It has 2 ¾ turns. Divided into three chambers by Basilar & Reissner’s membrane
  • Scala vestibuli (filled with perilymph )
  • Scala tympani (filled with perilymph )
  • Scala media (filled with endolymph )
The perilymph resembles ECF (high Na+, less K+)
Whereas the endolymph resembles ICF (More K+, less Na+).The K+ is secreted actively by Stria Vascularis

Organ of corti
– This is the sense organ for hearing. It is situated on the basilar membrane. The receptor for hearing are the hair cells


The hair cell processes are bathed in endolymph. Whereas the hair cell bases are bathed in perilymph. There are 4 rows of hair cells – 3 outer and 1 inner.

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