Chapter 9: (Module 10-The cochlea) Flashcards
bony labyrinth
a cavity that contains the inner ear; located within the petrous portion of the temporal bone.
membranous labyrinth
an endolymph-filled structure enclosed by the curves and coils of the bony labyrinth; the membranous labyrinth contains the semicircular ducts, utricle, saccule, and cochlea, which are connected via small communication channels.
cochlea
part of the inner ear that contains the sense organ of hearing (organ of Corti); the location which mechanical motions generated by sound are coded into nerve impulses for transition to the central nervous system.
organ of Corti
the sense organ of hearing that runs along the entire length of the basilar membrane; located on the scala media site of the basilar membrane.
basilar membrane
thinest and stiffest at the base of the cochlea
thickest and most flaccid at the apex
TONOTOPIC ORGANIZATION
the membrane that separates the scala media from the scala tympani; the organ of Corti is located on the scala media side of this membrane.
Held in place by the spiral ligament on one side and the spiral limbus on the other
scala media
Cochlear duct
filled with endolymph
the cochlear portion of the membranous labyrinth
scala tympani
filled with perilymph
connects with the scala vestibule at the helicortema located at the apex of the cochlea.
one part of the cochlear portion of the bony labyrinth; the scala tympani extends along the length of the cochlea from the helicotrema to the round window
scala vestibuli
filled with perilymph
continuous with the vestibule at the base of the cochlea
one part of the cochlear portion of the bony labyrinth; the scala vestibli extends along the length of the cochlea from the vestibule to the helicotrema.
helicortrema
a narrow passage at the apex of the cochlea at which the scala tympani and scala vestibule are connected.
perilymph
“peri”- out or around
the fluid that fills the bony labyrinth (scala vestibule and scala tympani of the inner ear); perilymph is high in sodium (Na) and low in potassium (K).
endolymph
“endo”- in
fluid located within the membranous labyrinth of the inner ear (in the scala media of the cochlea);this fluid is high in potassium (K) and low in sodium (Na).
base (of the cochlea)
the widest coil of the spiral of the cochlea
apex (of the cochlea)
the narrowest end of the spiral of the cochlea, where the scala tympani and scala vestibule join.
modiolus
bony core
the central bony channel of the cochlea within which the spiral ganglia are located.
spiral gaglia
the collection of cell bodies of the afferent auditor nerves; located in Rosenthal’s canal within the modiolus of the cochlea
spiral lamina
auditor nerve enters spiral lamina through holes called habenula perforata.
a spiral, corkscrew-shaped bony shelf that projects from the side of the modulus and partially divides the cochlear tunnel into smaller sections.
spiral ligament
a ligament that connects the basilar membrane with the lateral wall of the bony labyrinth
spiral limbus
the medial attachment point for Reissner’s membrane
Reissner’s membrane
the membrane that separates the scala media from the scala vestibule.
Rosenthal’s canal
*part of auditory nerve
channel in the center of the modulus through which the auditory nerve fibers travel.
tonotopic organization
the corresponded between stimulation frequency and place of stimulation along the cochlea.
stria vascularis
located on the outside edge of the scala media
the vascular strip on the lateral wall of the scala media.
tectorial membrane
attached to the spiral limbus and extends out over the organ of Corti.
reticular lamina
forms the upper surface of the organ of corti
the upper surface of the organ of Corti formed by the tops of the hair cells and supporting cells; the hair cell stereocillia project through this into the endolymph of the scala media.
stereocillia
tiny hair-like projections from one end of a hair cell that are responsible for changing mechanical motion into electrochemical impulses that can be transmitted by the nervous system.
connected by cross links
side to side
row to row
tip to side (also known as tip link)
a fiber that connects adjacent stereo cilia between
the top (smaller cell) and the side (larger cell) of
adjacent stereocillia across rows on a hair cell
habenula perforata
tiny holes in the spiral lamina through which auditory nerve fibers pass.
Traveling wave
transverse wave
mechanical wave in which the particles of the medium are displaced in a direction that is perpendicular to the direction of the wave propagation through the medium.
ions
a charged particle; +ions are called cations and -ions are called anions
electric potential
the force between 2 opposing charges
an electric charge measured in reference to a specific point.
bioelectric potentials
electric potentials in the ear are created by ions in perilymph, enrollymph and hair cells.
the electric potentials (differences in electrical charge) existing between various areas within the human body
endocochlear potential (EP)
the resting potential (+80 mV) between the endolymph in the scala media and the perilymph in the scala vestibule and scala tympani.
resting potentials
a difference in electric charge between two areas in the human body (bioelectric potential) that exists in the natural state of an organism without the nee for external stimulation.
IHC have a resting potential of -40mV compared to the perilymph
OHC have a resting potential of -70 mV to the perilymph
**the resting potential of the hair cells is lower than the endolymph by
120mV IHC’s
150mC OHC’s
stimulus-related potential action potentials neural potentials neural impulses nerve impulses
electrical potentials that are generated by stimulation.
compound action potential (CAP)
an alternating current potential generated by the simultaneous action potentials from many different neurons; the magnitude of the CAP depends on the number of activated neurons.
direct current (DC) potential
a current produced by unidirectional voltage
alternating current (AC) potential
a current that periodically changes its direction; a current produced by an alternating voltage
electromotility
motility
the ability of outer hair cells to change dimensions in response to changes in the electrical potential if the cell.
prestin
a protein located in the outer hair cell wall that is associated with outer hair cell motility
otoacustic emissions
OAE’S
sounds that are observed in the outer ear as a result of vibrations generated in the inner ear.
very low-intensity sounds caused by the electromoility function of the outer hair cells; these sounds can be recorded in the ear canal via signal-averaging techniques.
cuticular plate
a thickening at the top edge of the hair cell where the stereo cilia are firmly anchored to the hair cell.
Inner hair cells (IHC’s)
a single row of flask-shaped sensory cells in the organ of Corgi of the inner ear; each inner ear contains approximately 3500 inner hair cells.
IHC’s in action
the IHC’s release neurotransmitters into the synaptic cleft.
neurotransmitters bind to specialized receptor sites on auditory nerve endings.
Outer hair cells (OHC’s)
cylindrically shaped cells in the organ of Corti that are generally arranged in three rows along the length of the basilar membrane; there are approximately 12,000 outer hair cells per ear; these cells change in length in response to voltage changes across the cell membrane.
Organ of Corti support cells
*don’t need to know the names, just that they are there
vestibulocochlear nerve
the eighth cranial nerve (CN VIII) which conveys sensory information about hearing and balance to the central auditory nervous system.
cochlear portion of this nerve is also called the auditory nerve.
ganglion
lots of nerves together
a group of cell bodies in the peripheral nervous system.
neuron
individual cells from a nerve
a cell that is capable of transmitting electrochemical information within the nervous system of the body.
Afferent and Efferent
Afferent neurons
carries information from the peripheral nervous system to central nervous system,
a neuron that carries sensory information (touch, taste, smell, hearing, vision) from the peripheral nervous system to the central nervous system.
OUT to IN
inner hair cells
Efferent neurons
carries information from the central nervous system to the peripheral nervous system.
a neuron that carries information from the central nervous system to the peripheral nervous system.
IN to OUT
outer hair cells
myelin
a fatty covering that speeds the conduction of nerve impulses
Olivocochlear bundle (OCB)
EFFERENT nerve tiger that projects from the peroolivary nuclei of the superior olivary complex to the cochlea; composed of medial olivocochlear neurons and lateral olivochochlear neurons
superior olivary complex (SOC)
a group of nuclei in the CANS located in the pons; the first location in the CANS that receives projections from both ears; this center plays a major role in coding for localization
(Auditory nerve)
pg 139 of note book)
auditory neurons enter the spiral lamina via holes called habitual perforata.
cell bodies from these neurons, called spiral gaggles, are located in Rosenthal’s Canal in the modiolus.
Place theory of hearing
the theory attempting to explain the process of hearing based on place coding.
Place code
cochlear coding of auditory signals in which the place of maximal stimulation along the basilar membrane conveys the frequency of a sound wave.
characteristic frequency (CF) the frequency at which individual hair cells and nerve cells are tuned to respond most effectively.
Periodicity theory
Temporal theory
states that frequency is coded based on the period of the waveform. In other words the rate or frequency of neural impulses is the mechanism for coding frequency,
we get the nerve responding in phase with the wave
(this is also true)
