Slide 1
The inner ear senses movement as well as sound
The inner ear contains organs that help detect head movement and orientation. Their signals contribute to balance and stable vision.
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The brain combines these signals with information from the eyes and the body. Balance is therefore a coordinated estimate, rather than a measurement supplied by one organ alone.
Slide 2
Fluid-filled canals respond to head rotation
Semicircular canals are fluid-filled loops arranged in different planes. Head rotation shifts the relationship between the fluid and sensitive structures.
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Hair cells convert mechanical bending into changes in nerve activity. Their name refers to small projections involved in sensing, not to ordinary hairs growing in the ear canal.
Slide 3
The utricle and saccule sense straight acceleration and tilt
The utricle and saccule help sense linear acceleration and head tilt. Tiny mineral particles add weight to their sensory covering.
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These particles are called otoconia. Their inertia and response to gravity influence the underlying hair cells, giving the system information different from that provided by the semicircular canals.
Slide 4
Their signals help the eyes keep an object in view
Vestibular signals help coordinate eye movements when the head moves. This allows a viewed object to remain relatively stable on the retina.
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The same system contributes to postural responses that keep the body oriented. A disturbance can affect gaze and movement together because both use related information about head motion.
Slide 5
Conflicting signals do not identify one single cause of imbalance
A mismatch among sensory signals can make orientation difficult. Balance problems have several possible causes and require context to interpret.
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Researchers examine how the nervous system adapts when one source of information changes. Understanding adaptation is different from assuming every episode of dizziness begins in the inner ear.
Sources
- Balance Disorders
NIDCD, NIH
- Balance Program
NIDCD, NIH