Physiology of Balance Flashcards
What are the six semicircular canals?
- Left Anterior
- Right Anterior
- Left Lateral
- Right Lateral
- Left Posterior
- Right Posterior
What do the semicircular canals detect?
Head rotation in all directions
How many otolith organs are there?
4
How are the semicircular canals arranged?
At right angles to each other
What are the functional pairings of the semicircular canals?
- Left Anterior and Right Posterior
- Right Anterior and Left Posterior
- Left Lateral and Right Lateral
Why aren’t the otolith organs at exactly right angles to each other?
It allows them to resolve head tilt and linear acceleration in all directions.
What are the two types of vestibular hair cells found in the semicircular canals and otolith organs?
Type I: Surrounded by afferent nerve calyx but aren’t directly contacted by efferent nerve fibres (Minority)
Type II: Innervated by both afferent and efferent nerve fibres (Majority)
What is nystagmus?
Slow eye movements followed by fast eye movements during continuous head rotation.
What are the two types of nystagmus?
Physiological: Elicited in normal individuals during head rotation.
Spontaneous: When the eyes move rhythmically from side to side in the absence of head movements
What are the causes of nystagmus?
- Damage to one of the canals
- Differences in vestibular nerve firing when the head is stable
What is caloric testing used for?
To test the function of the brainstem in an unconscious patient
What do receptors in the otolith organs detect?
- Linear acceleration
- Tilting of the head
What are the causes of vestibular disorders?
- Ear infections
- Head injuries
- Whiplash
- Ageing
- Certain drugs
What are some disorders of the vestibular system?
- Trauma (to CN VIII)
- Dizziness
- Benign paroxysmal positional vertigo (BPPV) which is vertigo caused by changes in head position
- Meniere’s diseases which is a progressive disease caused by excess fluid in the inner ear (leading to episodes of vertigo and progressive hearing loss)
