Lecture 10:Anatomy and Functions of the Ear
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Questions and Answers

What is the function of the cochlea in the ear?

  • Detection of sound (correct)
  • Maintaining body balance
  • Transmitting sound waves to the brain
  • Producing ear wax

    • What is the role of the pinna in the external ear?

  • Producing ear wax
  • Collecting and amplifying sound waves (correct)
  • Equalizing air pressure
  • Maintaining body balance

    • What is the function of the vestibular apparatus?

  • Maintaining body balance (correct)
  • Producing ear wax
  • Amplifying sound waves
  • Detection of sound

    • How much does the middle ear amplify sound waves?

    <p>By 22 times</p> Signup and view all the answers

    What are the three ossicles in the middle ear?

    <p>Malleus, Incus, Stapes</p> Signup and view all the answers

    What is the function of the tensor tympani muscle?

    <p>To protect the ear from loud noise</p> Signup and view all the answers

    What is the function of the auditory tube?

    <p>To equalize air pressure on both sides of the tympanic membrane</p> Signup and view all the answers

    Where does the ear canal end?

    <p>At the eardrum</p> Signup and view all the answers

    What is the function of the three bones of the middle ear?

    <p>To vibrate and transfer sound wave energy</p> Signup and view all the answers

    What happens when the staples vibrate against the oval window?

    <p>Fluid waves are generated within the vestibular duct</p> Signup and view all the answers

    What is the function of the hair cells in the cochlear duct?

    <p>To convert fluid waves into electrical impulses</p> Signup and view all the answers

    What happens when the basilar membrane moves upwards?

    <p>The stereocilia bend towards the tallest stereocilium</p> Signup and view all the answers

    What is the result of the entry of K+ ions into the hair cell?

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

    What happens when the basilar membrane moves in the opposite direction?

    <p>The stereocilia bend away from the tallest stereocilium</p> Signup and view all the answers

    What is the function of the vestibulocochlear nerve?

    <p>To transmit electrical impulses from the cochlear nerve to the brain</p> Signup and view all the answers

    What is the final destination of the auditory pathway?

    <p>The auditory cortex</p> Signup and view all the answers

    What is the primary function of the stapedius muscle?

    <p>To dampen the ossicular chain vibration</p> Signup and view all the answers

    Which part of the inner ear is responsible for balance?

    <p>Vestibule and semicircular canals</p> Signup and view all the answers

    What is the range of sound frequencies that the human ear can detect?

    <p>20-20,000 Hz</p> Signup and view all the answers

    What is the name of the membrane that separates the middle ear from the inner ear?

    <p>Oval window</p> Signup and view all the answers

    What is the function of the hair cells in the spiral organ of Corti?

    <p>To convert sound waves into nerve impulses</p> Signup and view all the answers

    What is the name of the bony structure that houses the inner ear?

    <p>Temporal bone</p> Signup and view all the answers

    What is the mechanism by which sound waves are transmitted to the inner ear?

    <p>Sound waves strike the tympanic membrane and become vibrations</p> Signup and view all the answers

    What is the name of the nerve that transmits auditory information from the inner ear to the brain?

    <p>Auditory nerve</p> Signup and view all the answers

    The cochlear nucleus receives information from which side of the body?

    <p>One side (ipsilateral)</p> Signup and view all the answers

    What is the function of the superior olivary nucleus?

    <p>To interpret and combine input from the cochlear nucleus</p> Signup and view all the answers

    What is the function of the vestibule?

    <p>Monitoring static equilibrium</p> Signup and view all the answers

    Where do fibers carrying auditory information from the inferior colliculus project to?

    <p>The medial geniculate nucleus of the thalamus</p> Signup and view all the answers

    What type of acceleration is monitored by the semicircular canals?

    <p>Angular acceleration</p> Signup and view all the answers

    Where are the maculae (static equilibrium receptors) located?

    <p>In the utricle and saccule</p> Signup and view all the answers

    What happens to hearing in cases of supranuclear lesions?

    <p>Hearing is not significantly impaired</p> Signup and view all the answers

    What is the final destination of auditory information in the brain?

    <p>The auditory cortex</p> Signup and view all the answers

    What is the function of the otolithic membrane?

    <p>To detect changes in head position</p> Signup and view all the answers

    What is the primary function of the utricle and saccule?

    <p>Balance and equilibrium</p> Signup and view all the answers

    What happens to otoliths when the head is tilted?

    <p>They roll in response to gravity</p> Signup and view all the answers

    What is the purpose of the crista ampullaris?

    <p>To detect angular or rotatory movements</p> Signup and view all the answers

    What is the gel-like structure that the hair cells are embedded in within the crista ampullaris?

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

    What is the function of the semicircular ducts?

    <p>To detect angular or rotatory movements</p> Signup and view all the answers

    What is the direction of one of the semicircular ducts?

    <p>Horizontal plane</p> Signup and view all the answers

    What is the role of the vestibulocochlear nerve?

    <p>To transmit balance and equilibrium information</p> Signup and view all the answers

    Study Notes

    Functions of the Ear

    • The ear has two main functions: hearing (detection of sound) and equilibrium (maintenance of body balance)
    • Hearing involves the detection of sound waves by the cochlea
    • Equilibrium involves the maintenance of body balance by the vestibule and semicircular canals

    Parts of the Ear

    • The ear consists of three main regions: external ear, middle ear, and inner ear
    • The external ear (outer ear) collects sound waves and channels them down the ear canal
    • The middle ear transmits sound waves to the inner ear, amplifying sound energy
    • The inner ear consists of two sensory systems: cochlea (hearing) and vestibular apparatus (balance)

    External Ear

    • Plays a role in sound localization
    • Amplifies sound by approximately 5-6 dB
    • Pinna (auricle) collects sound waves and channels them down the ear canal
    • Ceruminous (wax) glands produce ear wax, trapping foreign particles and preventing them from entering the ear
    • Ends at the tympanic membrane (eardrum), which vibrates when sound waves hit it and transmits the sound waves to the middle ear

    Middle Ear

    • Contains three ossicles (smallest bones): malleus (hammer), incus (anvil), and stapes (stirrup)
    • Ossicles are connected to each other and transmit sound waves from the tympanic membrane to the inner ear
    • Amplifies sound waves by 22 times
    • The auditory tube (Eustachian tube) connects the middle ear with the throat (nasopharynx), helping to equalize air pressure on both sides of the tympanic membrane during yawning or swallowing

    Muscles of the Middle Ear

    • Two muscles: tensor tympani and stapedius
    • Tensor tympani muscle:
      • Contracts in response to loud sounds, pulling the tympanic membrane inward and restricting its freedom of movement
      • Protects the ear from loud noise or trauma
    • Stapedius muscle:
      • Smallest muscle in the body
      • Contracts in response to loud sounds, damping the ossicular chain vibration and limiting potential damage

    Inner Ear

    • Most complex portion of the ear
    • A maze of bony chambers within the temporal bone
    • Consists of three parts: semicircular canals (balance), vestibule (balance), and cochlea (hearing)

    Hearing (Audition)

    • Hearing is the transduction of sound waves into electrical signals
    • Spiral organ of Corti is housed within the cochlear duct and contains hair cells (hearing receptors)
    • Hair cells convert sound waves into nerve impulses, transmitted via the auditory nerves to the brain for perception and interpretation as sound
    • Cochlea encodes auditory stimuli for frequencies between 20 and 20,000 Hz

    Mechanism of Hearing

    • Sound waves in the ear canal strike the tympanic membrane (eardrum) and become vibrations
    • Vibrations of the stapes against the oval window are converted into fluid waves within the vestibular duct
    • Fluid waves push on the membranes of the cochlear duct, activating the sensory hair cell receptors
    • Activated hair cells stimulate the auditory nerve, transmitting the signal to the brain for perception and interpretation as sound

    Auditory Pathway

    • The nerve impulse travels along the vestibulocochlear nerve, synapsing with neurons in the cochlear nuclei of the medulla
    • From the cochlear nucleus, some fibers synapse at the ipsilateral superior olivary nuclei, while most fibers decussate to the contralateral superior olivary nuclei
    • Fibers from superior olivary nuclei project upwards through the lateral lemniscus to reach the inferior colliculus nucleus
    • Axons carrying auditory information project to the medial geniculate nucleus of the thalamus, then to the auditory cortex in the temporal lobe of the cerebral cortex for interpretation as hearing

    Physiology of Balance: Vestibular Apparatus

    • The vestibular apparatus consists of the vestibule (monitoring static equilibrium) and the semicircular canals (monitoring dynamic equilibrium)
    • The vestibule is responsible for monitoring static equilibrium, detecting changes in position of the head in space with respect to the pull of gravity
    • The semicircular canals are responsible for monitoring dynamic equilibrium, detecting angular or rotatory movements of the head

    Vestibule: Utricle and Saccule

    • Maculae (static equilibrium receptors) are located within the membranous sacs of the vestibule (utricle and saccule)
    • Each macula is a patch of hair cells with stereocilia embedded in the otolithic membrane (a viscous gel containing calcium crystals called otoliths)
    • When the head tilts, otoliths roll in response to the pull of gravity, creating a pull on the otolithic membrane and bending of macula hair cells
    • The hair cells become activated and send impulses along the vestibulocochlear nerve to the brain stem and cerebellum, informing it of the head position in space

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    Description

    This quiz covers the structure and functions of the human ear, including hearing and equilibrium, and the different parts of the ear.

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