Following my previous post, we’ll be continuing to review the basic concepts of the vestibular system.
The vestibular labyrinth is composed of 3 semicircular canals which serve as tubes that are situated in a plane in which the head can rotate. Each of the canals can detect one of the following head movements:
- Lateral tube (side to side motion)
- Posterior tube (tilting left and right motion)
- Anterior tube (nodding motion, forward/back head movement)
The semicircular canals contain a fluid called endolymph. When the head is rotated, there’s movement of endolymph through the canal corresponding to the plane of movement. The endolymph then flows into an expansion of the canal called the ampulla.
The ampulla of each semicircular canal contains hair cells, which are the sensory receptors of the vestibular system. On the top of each hair cell, there’s a collection of small “hairs” known as stereocilia. A structure called the cupula is also located in the ampulla, it serves to separate the endolymph from the hair cells.
The movement of the endolymph in the ampulla causes the movement of the stereocilia which leads to the release of neurotransmitters. These neurotransmitters send information about the plane of movement to the brain.
1. Khan S, Chang R (2013). Anatomy of the vestibular system: A review NeuroRehabilitation, 32 (3), 437-443