22 Questions
What is the primary function of the utricle and saccule?
To detect linear acceleration, deceleration, and static tilt of the head
What is the name of the fluid that fills the semicircular canals?
Endolymph
What is the bilateral receptor system located in the membranous labyrinth?
Vestibular apparatus
What is the reason people feel dizzy after spinning around and suddenly stopping?
The endolymph in the ears is still moving due to inertia
What is the central vestibular system located in?
The brainstem and cerebellum
What is the name of the nerve that transmits information from the peripheral vestibular system to the central nervous system?
Vestibulocochlear nerve
What is the function of the hair cells located in the macula of the otolith organs?
To detect linear acceleration and deceleration
What is the name of the structures that make up the kinetic labyrinth?
Semicircular canals
What causes the stereocilia to bend in the direction of linear acceleration?
Gravity and inertial forces acting simultaneously on the otolith
What is the role of the otolith vestibular hair cells?
To either activate or inhibit to alert about a change in the position of the head
What is the characteristic of vestibular hair cells at the resting stage?
They are tonically active cells
Where do the sensory vestibular fibers arrive?
4 vestibular nuclei and the cerebellum
What happens to the action potential frequency when the stereocilia are bent towards one side?
The frequency increases
Where are the vestibular hair cell canals located?
In the cristae ampullaris of the semicircular canals
What is the pathway of the vestibular nuclei to the spinal cord?
Lateral and medial vestibulospinal tracts
What is the function of the cupula?
To cover the vestibular hair cells
What is the function of the fastigial nucleus and flocculonodular lobe?
To process information from the vestibular nuclei and cerebellum
What is the function of the thalamus in the vestibular pathway?
To relay information to the cortex for conscious vestibular information
What happens to the cupula during angular acceleration of the head?
It is displaced
What is the function of the maculae in the otolith organ?
To sense linear acceleration
Why can someone feel the car stopping when they are blindfolded?
Because the macula of utricle is horizontally oriented
Why can someone feel themselves going up or down when they are inside an elevator?
Because the macula of saccule is vertically oriented
Study Notes
Vestibular System
- Divided into peripheral and central systems
- Peripheral system located outside of the brain, composed of vestibular apparatus in membranous labyrinth and vestibular portion of vestibulocochlear nerve (Cranial nerve 8)
Peripheral Vestibular System
- Vestibular apparatus consists of 3 semicircular canals (kinetic labyrinth) and 2 otolith organs (static labyrinth)
- Semicircular canals are filled with endolymph and surrounded by perilymph
- Otolith organs consist of utricle and saccule, which detect linear acceleration, deceleration, and static tilt of the head
Central Vestibular System
- Located in cerebellum and brainstem, contains 4 pairs of vestibular nuclei on each side
- Functions include maintaining balance and coordination of eye-head-body movements
Vestibular Hair Cells
- Located in macula of otolith organs
- Tonic ally active cells at resting stage with constant firing rate
- Bending of stereocilia towards one side increases action potential frequency, while bending in opposite direction decreases frequency
- Change in frequency of action potentials indicates which side the body is moving
- Hair cells in semicircular canals are covered by cupula, a gelatinous mass
- During angular acceleration, cupula is displaced, causing excitation or inhibition of hair cells
- All 6 canals activation provides precise indication of head movement in 3 dimensions
Otoliths
- Located in macula of otolith organ, with otolith mass overlaying vestibular hair cells
- Maculae have hair cells oriented in different directions to detect linear movement in different angles
- Macula of utricle is horizontally oriented, while macula of saccule is vertically oriented
- Maculae specialized for sensing linear acceleration, such as gravity acting on tilting head or head moving in straight line
- Gravitational or inertial forces cause stereocilia to bend in direction of linear acceleration
Vestibular Pathway
- Sensory vestibular fibers arrive at 4 vestibular nuclei and cerebellum
- Cerebellum projects to vestibular nuclei, spinal cord, brain stem, and thalamus
- Vestibular nuclei project to spinal cord, brain stem, cerebellum, and thalamus
Learn about the vestibular system, its peripheral and central components, and their roles in the human body. Quiz covers the membranous labyrinth and cranial nerve 8.
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