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During flight, a pilot may get sensory illusions about the pitch and bank angle. This is caused by the misinterpretation of signals from the vestibular apparatus. Which of the following is an element of the vestibular apparatus?
  • A
    The eardrum in the ear canal.
  • B
    The ossicles.
  • C
    The anterior semicircular canal.
  • D
    The cochlea in the inner ear.

Refer to figure.
Learning Objective (amongst others): List the main elements of the vestibular apparatus.

The vestibular system, located in the inner ear, consists of the vestibule and three semicircular canals. The utricle and saccule organs are within the vestibule, and are responsible for the perception of gravity and linear acceleration. The semicircular canals are oriented in three planes, each at 90º angle to the other two. This allows them to sense angular accelerations in yaw, pitch and roll. This question mentions the "anterior" semicircular canal, which is also called the superior canal, and is the one which senses pitch (nodding ones head is felt by this canal). The exact canals and their names are above the syllabus, though, which does not stop you answering this question.

They are extremely sensitive, and can be prone to errors such as "the leans", due to the way that they work, with fluid inside the canals that moves sensory hairs to detect the different accelerations. A common error is when a pilot has been turning for a while, and rolls out of the turn, their vestibular system has reset slightly in the turn, and now believes that they have banked the opposite direction, instead of being straight and level.

The other options all exist within the ear, but are parts of the auditory system, which allows us to hear sounds. The ossicles are made up of the malleus, incus and stapes.

Although both the vestibular system and the auditory system exist within the ear, they try and stay as isolated from each other as possible, although extremely loud noises can vibrate the vestibular apparatus, giving balance problems.

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