Lecture 26: Vestibular System
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Questions and Answers

What is the effect of deflecting the stereocilia toward the kinocilium?

  • It depolarizes the cell membrane. (correct)
  • It inhibits the release of neurotransmitters.
  • It hyperpolarizes the cell membrane.
  • It opens K+ channels allowing K+ to flow out.

    • What happens to the cell membrane after the stimulus subsides?

  • Voltage-gated K+ channels remain closed.
  • The cell membrane hyperpolarizes and returns to resting potential. (correct)
  • The cell membrane remains depolarized for an extended period.
  • Calcium channels stay open longer, increasing neurotransmitter release.

    • How does deflection of the stereocilia away from the kinocilium affect the neurotransmitter release rate?

  • It increases the neurotransmitter release rate.
  • It results in only increased firing rate of afferent fibers.
  • It has no effect on the neurotransmitter release rate.
  • It decreases the neurotransmitter release rate. (correct)

    • How many semicircular canals are present in the vestibular system?

    <p>Six total, three on each side.</p> Signup and view all the answers

    What characterizes the orientation of the semicircular canals?

    <p>They are oriented orthogonally to each other.</p> Signup and view all the answers

    What are the primary components of the vestibular system?

    <p>Semicircular canals and otolith organs</p> Signup and view all the answers

    What role does the vestibular system play during motion?

    <p>Maintains postural stability</p> Signup and view all the answers

    How do vestibular hair cells respond to motion?

    <p>Depolarization occurs when stereocilia move towards kinocilium</p> Signup and view all the answers

    What is the result of stereocilia movement away from the kinocilium?

    <p>Hyperpolarization of hair cells</p> Signup and view all the answers

    What fluid is found within the membranous canal of the semicircular canals?

    <p>Endolymph</p> Signup and view all the answers

    What happens to the afferent neurons at rest in the vestibular system?

    <p>They have spontaneous activity due to open Ca2+ channels</p> Signup and view all the answers

    Which structure connects the hair cell region in the ampulla to the opposite side?

    <p>Cupula</p> Signup and view all the answers

    What sensation might indicate an issue with the vestibular system?

    <p>Nausea and dizziness</p> Signup and view all the answers

    How do coplanar semicircular canals function during angular movements?

    <p>One excites while the other inhibits</p> Signup and view all the answers

    Which function does the vestibular system NOT support?

    <p>Enhancing auditory perception</p> Signup and view all the answers

    What common characteristic do the auditory and vestibular systems share?

    <p>Use of the same cranial nerve for innervation</p> Signup and view all the answers

    What primary structure detects motion within the vestibular system?

    <p>Semicircular canals</p> Signup and view all the answers

    In what way does angular head motion affect the endolymph in the semicircular canals?

    <p>It induces inertially-driven endolymph motion</p> Signup and view all the answers

    What results from the movement of stereocilia towards the kinocilium?

    <p>Increased transmitter release from the hair cells</p> Signup and view all the answers

    What happens if there is a problem with the common fluid system of the auditory and vestibular systems?

    <p>Both hearing and balance can be affected</p> Signup and view all the answers

    What characteristic of hair cells in the auditory and vestibular systems is similar?

    <p>They operate on nearly identical principles for motion detection</p> Signup and view all the answers

    What is the primary function of the utricle and saccule in the inner ear?

    <p>Provide information about linear acceleration</p> Signup and view all the answers

    How do the hair cells in the utricle and saccule differ in orientation?

    <p>Utricle hair cells are towards and saccule hair cells are away from the striola</p> Signup and view all the answers

    What initiates the motion of the otoliths in the utricle and saccule?

    <p>Inertially-driven motion due to acceleration</p> Signup and view all the answers

    What is the role of otoliths in the otolith organs?

    <p>Create a shear force on hair cell stereocilia during motion</p> Signup and view all the answers

    What distinguishes the orientation of hair cells in semicircular canals from those in otolith organs?

    <p>Otolith organs have hair cells oriented in opposing directions</p> Signup and view all the answers

    What is the significance of the striola in the otolith organs?

    <p>It creates a boundary for hair-cell polarity reversal</p> Signup and view all the answers

    How does the size of otolith crystals differ in humans compared to those found in other species, such as cats?

    <p>Human otoliths are smaller, ranging from 3 - 30 µm</p> Signup and view all the answers

    Which best describes the similarity between otolith organs and semicircular canals?

    <p>Both use hair cells to detect motion</p> Signup and view all the answers

    Study Notes

    Lecture 26: Vestibular System

    • The vestibular system, comprised of otolith organs (saccule and utricle) and semicircular canals, detects motion, maintains posture, and stabilizes images during head movement.
    • Vestibular receptors are located within the labyrinth of the inner ear.
    • These receptors provide the brain with information about head motion and orientation relative to gravity.
    • The system's functions are generally unnoticed unless experiencing unusual conditions, such as motion sickness.
    • This system works in tandem with other sensory information to coordinate body position.

    Topics

    • Vestibular Hair Cells
    • Semicircular Canals
    • Otolith Organs

    Overview

    • The vestibular system detects motion, posture, and image stability during head movement, relying on otolith organs (saccule and utricle) and semicircular canals.
    • Located in the labyrinth of the inner ear, these receptors convey motion and orientation data to the brain.

    Vestibular Hair Cells

    • Similar to auditory hair cells, motion is detected through hair cell (kinocilium and stereocilia) deflections.
    • Hair cell depolarization or hyperpolarization is direction dependent.
    • Depolarization is caused by stereocilia movement toward the kinocilium.
    • Hyperpolarization occurs with stereocilia movement away from the kinocilium.
    • This polarization change impacts firing rates of primary vestibular afferents to the brainstem.
    • At rest, spontaneous activity arises from calcium channels causing steady neurotransmitter release.
    • Movement in one direction stimulates the cranial 8th nerve, whereas the opposite direction inhibits firing.

    Semicircular Canals

    • Inner ear canals with endolymph, crucial for angular head acceleration detection during head rotation.
    • Each canal is oriented orthogonally to the other, effectively monitoring rotations in different planes.
    • A membranous canal carrying endolymph sits inside bony canals; perilymph occupies the outer space.
    • Endolymph inertia triggers cupula deflection, impacting hair cell stereocilia movement and altering firing rates in response to the angular head velocity.
    • Semicircular canals are paired—right and left horizontal; right anterior/left posterior; and left anterior/right posterior—functioning as push-pull pairs. Excitation of one leads to inhibition in the other.

    Otolith Organs: Utricle and Saccule

    • Otolith organs detect linear acceleration, including gravity and head position changes.
    • The utricle is horizontally oriented, while the saccule is vertically positioned.
    • Hair cells (the macula) embedded in gelatinous masses house calcium carbonate crystals (otoliths).
    • Otolith inertia, due to gravity or linear motion, causes shear forces on stereocilia.
    • Motion toward the kinocilium excites hair cells; motion away inhibits.
    • The striola in the macula divides the organ, causing differing hair-cell polarizations for linear motion detection in various directions.
    • Otolith organs and semicircular canals differ in how they detect motion.

    Similarities Between Auditory and Vestibular Systems

    • Shared fluid system (membranous labyrinth).
    • Both use hair cells to detect motion.
    • Both systems are innervated by branches of the same cranial nerve (8th).

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    NPB 110B Fall 2024 Lecture 26 Vestibular System I PDF

    Description

    Explore the vestibular system's intricate functions, including how the otolith organs and semicircular canals detect motion and maintain posture. This quiz will delve into the roles of vestibular hair cells and how they contribute to our sense of orientation and stability. Understand the system's significance, especially during unusual conditions like motion sickness.

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