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What structure within the inner ear allows us to hear?
What structure within the inner ear allows us to have balance?
What are the three sensory organs of the vestibular system?
Utricle (otolith organ)
Saccule (otolith organ)
Semicircular canal organs
How is the vestibular system organized?
Sensory organs surrounded by membranous labyrinth that is made up of connective tissue surrounded by boney layrinth within the petrous bone of the temporal lobe.
What is the function of the otolith organs?
To detect linear acceleration (change in velocity) of the head and position with respect to gravity.
What is the function of the semicircular canal organs?
Detect angular accelerations
How are the three semicircular canals organized?
Orthogoanl planes to each other. This allows detection of movements in the yaw, pitch and roll axes.
At what angle is the horizonal canal pitched?
30 degrees from the horizontal plane when the head is held upright
At what angle are the anterior and posterior canals pitched?
45 degree angle
How do the semicircular canals pair to transduce signals to the CNS?
The horizontal right and left act to send information to the CNS about horizontal rotation.
The anterior and posterior pair CONTRALATERALLY to send information about vertical head rotation.
What are the two otolith organs?
Saccule and Utricle
Why are the saccule and the utricle considered otolith organs?
They have particles of calcium carbonate crystals that live over the hair cells of the sensory epithelia.
What is a otoconia?
An individual calcium carbonate crystal they gibe mass to the hair cells
what is an otolithic membrain?
it is a gelatinous mass that overlays the appical surface of hair cells within the sensory epithelia and acts to hold the otoconia in place.
Which organs act together to signal postural changes and are therefore referred to as "static" receptors?
Saccule and utricle
What fluid bathes the hair cells within the vesticular system?
What is the tallest cilium located on one side of the hair bundle?
What does depoarizaiton of the hair cell cause?
Neurotransmitter release that causes increased frequency of action potential firing in the afferent nerve fiber.
Utricular hair bundles project vertically and tilt of head from the horizontal causes shear between the hair cells and the overlying otolithic membrain Therefore the utricule informs the brain of....
the position of the head with respect to gravity
The sacullar hair bundles project horizontally. What do they inform the brain of?
Verticle displacement of the head and inform the brain of linear acceleration in the vertical direction.
At what point does the utricle's axes of polarithy of the hair cells reverse?
along the central region of the epithelium called the striola
How are the hair bundles orientated in the saccule?
They are orientated facing away from the striola.
Why is the opposed orientation of the otolith organs so important?
Because at any given acceleration one will be maximally excited while the other is maximally inhibited.
What are the three canals that make up the semicircular canals?
What is the funciton of the semicircular canals?
Detecting angular acceleration.
What is the swelling at the base of each semicircular canal called?
What is the function of the ampulla?
This structure is important because it contains a specialized patch of epithelium called the crista which contains sensory hair cells.
WHat is the cupula?
It is a gel-like substance that covers the hair bundles in the crista
How are the kinocilia oriented in the horizontal canal?
They are facing towards the utricle.
How are the kinocilia oriented in the anterior and posterior canal?
They are facing away from the utricle
What is defined as the rate of change of anular velocity?
What disease is characterized by severe cases of vestibular dysfunction?
At what ganglion are the cell bodies of the vestibular afferents found?
Do projections from Scarpa's nucleus project to the ipsilateral or contralateral caudal pons and rostral medulla?
What are the four major vestibular nuclei that projections from Scarpa's ganglion project to?
Which of the four nuclei integrates information of the spinal column and the cerebellum?
the inferior nucleus and lateral
To which nuclei does the utricle project fibers to?
Middle, lateral, and inferior
At which of the three nuclei that the utricle sends fibers to that also receives cerebellar and spinal projections?
What are the axons called that leave the lateral nucleus and are derived from the spine, cerebellum, and the utricle?
Lateral vestibulospinal tract
Where do semicircular canal fibers project to?
Medial and superior vestibular nuclei
Cells that give rise to the medial longitudinal fasciculus carry information to what nucleus?
The medial vestibulospinal tract carries information from the medial vestiublar nucleus to what structure?
They are motor nuclei that carry information to the neck musculature.
The connections to oculomotor nuclei and to cervical motorneurons are important for coordinating what two actions?
Head and eye movement
Together the saccule , utricle and semicircular canals project to what nucleus?
The inferior vestibular nucleus which also receives information from spinal and cerebellar input.
Where does the inferior vestibular nucleus that receives information from the utricle, saccule, and semicircular canals project to?
The cerebellar vermis that in turn sends output to the reticular formation and other brainstem centers.
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