Vestibular system Flashcards
What is the vestibular system responsible for?
helping monitor the orientation of the head in 3 dimensional space. the data collected by the receptor apparatus is integrated in the CNS with visual and proprioceptive data
What does the integration of vestibular data and visual and proprioceptive data do?
1) Maintains general body equilibrium such as posture and balance
2) coordinates movements with the movements of the head (allows the maintenance of visual fixation on an object when the head moves through space
what are the parts that make up the vestibular system?
Parts of the the inner ear
vestibular division of the VIII nerve and CNS pathways
what makes up the vestibular portion of the inner ear?
osseous labyrinth
Membrancous labyrinth
saccule and utricle
What makes up the osseous labyrinth of the vestibular portion of the inner ear?
vestibule
semicircular canal
what makes up the membranous labyrinth of the vestibular portion of the inner ear?
Utricle and saccule (within the vestibule)
semicircular ducts
What are the saccule and utricle?
dilation of the membranous labyrinth and filled with endolymph
what is found in the wall of each saccule and utricle?
a patch of sensory epithelium which are the receptors of the saccule and utricle known as the macula (utricle and sacule)
what are the maculae?
The maculae are specialized mechanoreceptors that monitor the position of the head (static and kinetic)
what is found in the macula?
hair cells
otolithic membrane
dendrites of primary vestibular neurons
What are the hair cells of the macula?
sensory cells made of sterocilia that project from the apical edge
what is the single longer stereocilia projection of the macula known as ?
kinocilium
Where are the hair cells of the macula found?
embedded into the otolithic membrane
What is the otolithic membrane?
gelatinous membrane containing otoliths (crystals of protein of calcium carbonate
what do the dendrites of the primary vestibular neurons found in the macula and do and where are the neuron cell bodies found?
the dendrites engage the base of each hair cell and the neuron cell bodies are in Scarpa’s ganglion
What happens to the maculae receptors as one moves their head from a static position (linear or tilting movements)?
the maculae receptors change their excitability (from static discharge)which results in an increase or decrease of discharge in the macula
What is the effect of head movement on the otolithic membrane and the hairs on the macula?
The otolithic membrane shifts its position relative to the hair cells and the hairs are bent. this causes the hair cells to excite and the vestibular data generated is relayed to the CNS via primary vestibular neurons
What best monitors tilting movements of the head and linear acceleration and deceleration?
The macula utricle and macula saccule
what happens to the maculae during constant velocity?
Maculae reach a static discharge
how many semicircular ducts are there per ear?
3 (anterior, posterior, lateral/horizontal) that all connect to the utricle
How is each semicircular duct orientated?
at a right angle to one another
How is the posterior duct of the semicircular ducts orientated?
in the vertical plane (parallel to the long axis of the petrous temporal bone)
How is the anterior duct of the semicircular ducts orientated?
in the vertical plane (perpendicular to the long axis of the petrous temporal bone)
How is the lateral/horizontal duct of the semicircular ducts orientated?
Slopes posteriorly and inferiorly 30 degrees to the horizontal plane
which direction is the ampulla for the lateral semicircular duct positioned?
Anteriorly
what are semicircular ducts filled with?
endolymph and surrounded by perilymph
What is an ampulla?
dilation at one end of each duct
where is the crista ampullaris found?
patch of specialized sensory epithelium along the wall of each ampulla
what is the crista ampullaris?
specialized mechanoreceptor that monitors angular/rotational movement of the the head
which ducts best detect movements in the vertical plane
Anterior and posterior ducts
which ducts best detect movements in the horizontal plane?
lateral ducts
what makes up the crista ampullaris?
hair cells
dendrites of primary vestibular neurons
does the crista ampullaris have otoliths?
no
what are the hair cells of the crista ampullaris?
Stereocilia projections from the apical edge along with a single kinocilium
Where are the hairs of the crista ampullaris embedded?
in a gelatinous membrane called the cupula
what do the dendrites of the primary vestibular neurons found in the crista ampullaris do and where are the neuron cell bodies found?
the dendrites engage the base of each hair cell and the neuron cell bodies are in Scarpa’s ganglion
when the head undergoes angular/rotational motion what happens to the crista ampullaris?
Their excitability (from static discharge) changes and an increase or decreased discharge occurs
What does rotation of the head cause for the semicircular ducts?
rotational motion of the head results in parallel rotation of the semicircular ducts
what happens to the endolymph inside the semicircular canals during acceleration of the head?
the movement of endolymph inside the ducts lags behind the movment of the wall of the duct which therefore cause a net movement of endolymph in the opposite direction
What does the net movement of endolymph in an opposite direction do in regards to data relay?
The net movement of endolymph inside the semicircular ducts cause deflection of the cupola and results in a change in the excitability of the hair cells allowing vestibular data to be relayed to the CNS via the primary vestibular neurons
What occurs in the right lateral duct when the head is rotated to the right ?
Endolymph flows in the right lateral duct moves from the duct through the ampulla and into the utricle
What is movement from the duct towards the ampulla termed?
ampullopedal flow
What occurs in the left lateral duct when the head is rotated to the right ?
Endolymph flow in the left lateral duct is from the utricle through the ampulla into the duct
What is movement from the ampulla into the duct is termed?
ampullofugal flow
In the lateral semicircular ducts, which movement facilitates the crista or increases discharge?
Ampullopedal movement
In the lateral semicircular ducts, which movement inhibits the crista or decreases discharge?
Ampullofugal movement
What motions of the head do lateral semicircular ducts best monitor?
Rotation of the head in the horizontal plane
What happens to the discharge/excitability of the crista when the head maintains rotation at a constant velocity?
Left and right crista ampullaris reach a static discharge and ultimately the brain doesn’t know the head is rotating
