Vestibular Anatomy and Physiology Flashcards
(53 cards)
What is the primary role of the balance system?
To allow us to interact and maintain contact with out surroundings
As we move through our environment, information is gathered through the visual, somatosensory, and vestibular senses and sent to the brain for integration, perception and processing
What percentage does vestibular information contribute to body stability?
65%
Main contributor
Standing balance, however, does not rely on primarily on vestibular information
Proprioception is the major contributor to standing balance
When proprioceptive input is not helpful vision becomes the primary source of information
What is the bony labyrinth filled with?
Perilymph
What is the membranous labyrinth filled with?
Endolymph
What are the 5 sensory organs housed within each membranous labyrinth (10 total)?
Utricle macula
Saccule macula
Three cristae ampullaris
What are known as otolithic structures?
Utricle and saccule
What does the utricle do?
Plays a large role in postural control and primarily senses changes in orientation with respect to gravity. Such as moving forward in a car
What do gravity and linear motion exert forces on?
The otolithic sensory structures
What hair cells in the vestibular system stimulated by?
Mostly motion of the fluid
Sometimes sound
Does the utricle have a direct route to the SCCs?
Yes, the saccule does not
What are otoconia?
A layer of calcium carbonate crystals on the otoconial membrane (also known as the macula)
Protein matrix that holds all of the crystals together (continuously generated throughout life)
Just below the otoconia lies a
gelatinous membrane through which
the hair cells project the stereocilia
What does movement of the otoconia result in?
Stimulation of the sensory cells
Otoliths respond transiently to linear acceleration and to head tilt
With a sudden forward movement, the supporting structures will move synchronously with the head
The density and weight of the otoconia cause them to lag behind head movement than they catch up after several seconds of linear movement (utricular response is exhausted)
A tilt of the head causes a prolonged response from the utricle (why we think that the utricle is the primary sensor for orientation to gravity and plays an important role in postural stability)
What stimulates the saccule?
Up/down
Vertical stimulation
Debate on whether the saccule can be stimulated in a lab
What is orthogonal?
Right angles to each other
Describes orientation of SCC
This arrangement causes the endolymph to flow toward or away from the ampullated end of the canal in at least one canal on each side
What is pitch?
Shaking head yes
What is yaw?
Shaking head no
What is roll?
Tilting head to the side
What are the sensory cells in the SCC?
Cristae and are housed in the ampulla
What is sitting on the cristae ampullaris?
Cupula (extends across the ampulla to close off the lumen of the canal)
Has a density that is similar to the endolymph (not sensitive to gravity)
What will movement that causes the stereocilia to flow toward the kinocilium result in?
Depolarization and an increase in electrical potential
Does ampullopetal always mean excitation?
No, only in the horizontal SCC
Other canals result in inhibition
Are there 2 vestibular nerve branches?
Yes
What are the three functions of the vestibular apparatus?
To provide a subjective sensation of movement and/or displacement in 3-dimensional space
To maintain upright body posture (balance)
To stabilize the eyes during head and head and body movement
Where are the cell bodies for the superior and inferior vestibular nerves?
Scarpa’s ganglion
