Unit 2_Auditory Flashcards
What is created by molecular vibration which produces sound waves?
Sound
What property of sound includes the following:
Speed of vibration
- # of complete wave cycles per second (Hz)
- Determines pitch
- 20-20,000 Hz
Frequency
What property of sound includes the following:
- Amplitude of sound waves
- Measured in decibels (dB)
- Correlated with perceived loudness
->intensity to hear a low freq. sound than a high frequency sound (there is not a 1-1 relationship between loudness and intensity because the human ear is not equally sensitive to all sound frequencies) - Intensity range = 0-120 dB
Intensity
What structure of the ear includes the following:
External auditory meatus
Tympanic membrane (TM) separates external ear from middle ear
Functions to collect sound waves
Serves as resonator
External ear
What structure of the ear includes the following:
Air-filled cavity between inner ear and tympanic membrane (TM)
Malleus, Incus, Stapes-transmit vibrations to inner ear
Stapes contacts oval window
Malleus contacts TM
Stapedius muscle contacts stapes & tensor tympani contacts malleus to dampen sound
Eustachian tube joins the middle ear to pharynx-adjusts pressure in middle ear to atmospheric pressure
Middle Ear
What structure of the ear includes the following:
- Allow effective transmission of sound to inner ear
- Reflexively (muscles) control movements of ossicles during loud noises
- Adjust for changes in pressure
Middle Ear
What structure of the ear includes the following:
Dual Functioning Mechanism
- Audition (Hearing)
- Equilibrium (Vestibular)
Inner Ear
What component of the inner ear includes the following:
Interconnected canals and cavities
Petrous portion of temporal bone
Contains membranous labyrinth
Bony Labyrinth
What component of the inner ear includes the following:
Fluid filled cochlea
Coiled system of ducts
Scala media or cochlear duct – (endolymph)
Scala tympani - round window – (perilymph)
Scala vestibuli - oval window – (perilymph)
Membranous Labyrinth
What kind of fluid does the coiled system of ducts (scala media or cochlear duct) contain?
endolymph
What kind of fluid does the coiled system of ducts is (Scala tympani) connected to the round window contain?
perilymph
What kind of fluid does the coiled system of ducts (Scala vestibuli) connected to the oval window contain?
perilymph
What pathway includes the goal to transform sound vibration to neural impulses which travel in CN VIII towards the CNS?
Scala media contains Organ of Corti which is sensory organ for hearing-contains sensory receptors and sits on the basilar membrane.
Hair cells are receptor cells that sit in the basilar membrane with hairs imbedded in the overlying tectorial membrane.
Hair cells innervated by peripheral processes of first order neurons in spiral ganglion.
Auditory Pathway
What is pushed upon by stapes to create waves within the scala vestibuli?
Oval window
What helps reduce the pressure in the scala tympani?
Round windows
What do the following steps describe?
- Tympanic membrane is displaced
- Stapes moves against oval window
- Pressure wave in canals
- Movement of basilar membrane
- Depolarization of receptor hair cells-generator potential
- Will generate receptor potential if threshold is reached
Sound to Receptor Potentials
What is known as different sound frequencies produce different wave form with maximum amplitude displacement at different locations on the basilar membrane?
Frequency Mapping
What sets up tonotopic organization of CNS representation of sounds?
Tonotopic Organization of Basilar Membrane
What nerve fibers tonotopically terminate in the dorsal & ventral cochlear nuclei?
Cochlear nerve fibers
What is tonotopically organized?
Cortex
What Help Use Auditory Information?
Associational Connections within the Cerebral Cortex
What localize sound sources?
Inter-aural intensity differences
What pathway includes the following:
Reflexive movements in response to noise
Inferior colliculi and SON, MLF, Vestibular nuclei, and spinal cord-turn head and eyes to sound
To CNVII for blink in response to loud noise
Reflex Pathways
What is a deficit to the Outer or Middle Ear?
Conductive hearing loss
What steps do the following describe:
Receptors
- Hair cells in scala media
First Order Neuron (bipolar) located in the spiral ganglion
- Enters brainstem as part of CN VIII synapses on cochlear nuclei in the medulla
2 primary pathways from cochlear nuclei
1. Fibers form the bilateral lateral lemniscus
Synapses in:
1. Inferior colliculus
2. Medial Geniculate
3. Primary Auditory Cortex
2. Terminate in superior olivary nucleus -Receives binaural convergence
Receptors to CNS
Where is the primary auditory cortex located?
Superior Temporal Gyrus
If there is an injury in the nervous system, there is an opportunity for information from both ears to make it to the primary auditory cortex. This is due to what?
1/2 primary pathways (Cortex) terminates in superior olivary nucleus and receives binaural convergence - goes to both sides.
What is a deficit to the Outer or Middle Ear?
Conductive hearing loss
What is a deficit to the Superior Olivary Nuclei (SON)?
Problems with Localization
What is a deficit to the Inner Ear to Cochlear N.?
Sensorineural hearing loss
What can lead to conductive hearing loss - Otitis Media?
Individuals with common or multiple ear infections
What can the following neuropathologies lead to?
Loud noise
Meniere’s Disease-deafness, tinnitus, dizziness
Acoustic Neuroma (slow growing mass on CN VIII)
Sensorineural Hearing Loss
What can blood supply loss lead to?
Labyrinthine (internal auditory) Arteries
What does the following describe?
- Information will travel via sound waves and reach our ear.
- It will travel through the external auditory meatus or the ear canal and make it’s way to the tympanic membrane.
- Tympanic membrane will vibrate and send information along the 3 bones of the inner ear which conduct vibration until it reaches the cochlea.
- The sound information is converted from a vibration of the bones to vibration of fluid.
- The fluid then vibrates the basilar membrane in the organ of corti in order to get an electrical signal.
- The electrical signal attaches to CN VIII via the cochlear division.
- The information then enters the medulla through the cochlear nuclei.
- One pathway sends information to both superior olivary nuclei to help with sound localization.
- One pathway crosses the CNS and sends information up to the medial geniculate nuclei and then to the primary auditory cortex.
Auditory pathway
