1. Hearing and Equilibrium
The Special Senses
Hearing and Equilibrium

2. The Special Senses
Auditory

3. Anatomy of the ear

4. Anatomy of the ear

5. Anatomy of the ear

6. Anatomy of the ear

12. Anatomy of the ear

15. Hearing Pathway

16. The Special Senses
Vestibular

17. Anatomy of the ear

18. Anatomy of the ear

19. Orientation of Vestibular Receptors
A. Lateral View
The horizontal semicircular canal & utricle:
Lie in a plane that is tilted anterodorsally
relative to the naso-occipital plane.
B. Axial View
Anterior & posterior semicircular canals, and
Saccule:
Arranged vertically in the head at 900 angles to
the horizontal canal.
The anterior & posterior canals:
Also lie at 900 angles to each other.
The anterior canal on one side is co-planar with
The posterior canal on the opposite side.
Text Fig. 22-3
© 2005 Elsevier

21. Ampulla of Semicircular canal

22. Hair Cell Activation Rotational head movements Angular accelerations
Displace endolymph in membranous ducts
Push cupula to one side or other
Displace stereocilia/kinocilium of
hair cells in same direction

23. Macula and otolith organ

28. Equilibrium PATHWAY

32. Ménière Disease
Disease results from a disruption of normal endolymph volume
Symptoms include: Severe vertigo
Positional nystagmus (nystagmus when head in a particular position)
Nausea
Affected individuals can also experience-unpredictable attacks of auditory & vestibular
symptoms: Vomiting
Tinnitus (ringing in ears)
Inability to make head movements
Inability to stand passively
Low frequency hearing loss
Treatment: administration of a diuretic (hydrochlorothiazide) & a salt restricted diet
Persistent condition: shunt implantation into swollen endolymphatic sac, or
delivery of a vestibulotoxic agents (gentamicin) into perilymph.

33. Benign Paroxysmal Positional Vertigo
common clinical disorder.
condition characterized by brief episodes of vertigo that coincide with particular changes in body position.
pathophysiology poorly understood.
posterior canal abnormalities are implicated.
otoconia crystals in the utricle may separate from the otolith membrane and become lodged in the cupula, causing abnormal cupula deflections. AND partial inflammation of cranial nerve VIII