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83 Cards in this Set
- Front
- Back
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Vertigo
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illusion of falling, spinning that usually involves loss of balance and is accompanied by neasuea and vomiting; can lead to spontaneous nystagmus; may be a sig of: inner ear disease, a tumor, or Meniere's disease
Sign of disturbance in vestibular system |
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What is the purpose of the "vestibular sense"?
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sends information to the brain about the head's position and, when the position changes, about the speed and direction of change
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Why is vestibular information vital?
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Important in:
-maintaining visual fixation during head movements -maintaining balance through postural adjustments -maintaining the proper relationship of head and body movements |
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What are the 3 systems working together to provide information to allow you to maintain equilibrium and balance?
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Vision, proprioceptive, and vestibular systems
-can get along with just 2/3 senses |
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The vestibular system and the cochlea make up which part of the ear?
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Inner ear
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Where does the labyrinth of the inner ear lie?
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Within the the petrous portion of the temporal bone, which is the hardest, densest bone of the body
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What is perilymph?
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a fluid almost identical to cerebrospinal fluid that is rich in sodium and low in potassium
Found in the scala vistibuli and the scala tympani |
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Where is the membranous labyrinth and what fluid does it contain?
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-it is suspended in the perilymph, and connected to the inner walls of the bony labyrinth by connective tissue fibers
-contains endolymph |
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What is endolymph?
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an extracellular fluid whose chemical composition is similar to that of intracellular fluid in that it has a high concentration of potassium ions and a low concentration of sodium ions
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How is the membranous labyrinth divided?
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Vestibular portion: the posterior superior part
Auditory portion or cochlear duct - anterior inferior part |
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What is the vestibular membranous labyrinth comprised of?
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-3 semicircular ducts
-ampulla: swellings of ducts -Crista ampullaris: patches of sensory epithelium within the ampulla |
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What are the 3 semicircular ducts/canals?
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1. horizontal, or lateral, semicircular canal
2. Superior, or anterior, semicircular duct 3. Inferior, or posterior, semicircular duct |
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What is the Crus Commune?
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the duct that is formed by one portion of the superior duct and one portion of the inferior duct
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What is the utriculus?
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a membranous epithelial bag, to which all 3 semicircular bags are connected
-it contains a patch of sensory epithelium called the macula of the utriculus |
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What is the utricular duct?
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-a duct that leads out of the utriculus and joins the saccular duct to form the endolymphatic duct
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What is the endolymphatic duct?
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-it leaves the petrous portion of the temporal bone and expands into the endolymphatic sac, which lies within the meninges on posterior surface of the petrous part of temporal bone
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What is the sacculus?
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bag of endolymph that is smaller than the utriculus
contains a patch of sensory epithelium called the macula connected to cochlear duct by the ductus reuniens |
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What is the ductus reuniens?
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it reunites the vestibular and auditory portions of the membranous labyrinth
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Semicircular canal
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each one is surrounded by perilymph and enclosed in a channel of the bony labyrinth
duct + perilymph filled bony channel |
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Vestibule
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large well of bone encased perilymph that surrounds the sacculus, the utriculus, and their ducts
-part of bony wall is the oval window where the footplate of the stapes is embedded |
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What are the 2 types of sensory epithelia within the vestibular system?
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1. crista ampullares - in semicircular ducts
2. maculae - in the utriculus and the sacculus *each composed of hair cells and supporting cells which hold hair cells in place |
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What is the significance of hair cells of the auditory and vestibular sensory epithelia?
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They are the transducers, changing mechanical stimuli into nerve impulses
the most sensitive mechanoreceptors of the body in contact with perilymph on all sides but one |
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What is the cuticular plate?
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a dense plate that holds together the hair cells
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What are tight junctions?
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areas of cell adhesion, where perilymph and endolymph cannot mix
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Type II vestibular hair cells
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columnal-shaped hair cells that have normal bouton-type nerve terminals synapsing on their base
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Type I vestibular hair cells
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flask-shaped hair cells that have extremely large synaptic endings surrounding much of the cell
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Calyces (singular: calyx)
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unusual nerve endings of type I vestibular hair cells
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What are the 2 types of cilia projected from the apical ends of all vestibular hair cells?
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Stereocilia and kinocilia
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Stereocilia
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anchored in the cutiuclar plate by a rootlet
-each stereocilia widens and contains many parallel molecules of actin that mix with mysoin to cause movement |
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Kinocilium
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-only one per hair cell
-longer than the stereocilium and has no actin -root extends through an opening in the cuticular plate and ends in the basal body -asymmetry in kinocilium polarizes the apical surface of hair cell |
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ciliary tuft
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all the cilia on each hair cell that are bounded together and function as a unit
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What happens when the ciliary tuft is bent in the direction of the kinocilium?
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potassium channels on the stereocilia are opened, allowing K+ ions to flow from the endolymph into the hair cells
-this inflow of K+ ions excites the hair cells to release neurotransmitters, that then excite the nerve endings that synapse on the base of the hair cells -neurons propagate action potentials to the vestibular division of the cranial nerve VIII into the brain |
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What happens when the ciliary tuft is bent in the direction away from the kinocilium?
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-causes inhibition of the system
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What are 2 important characteristics of this system?
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1. ciliary tufts are extremely sensitive - even weak forces will bend them and activate the system
2. system is directionally selective: towards kinocilium = excite; and away from kinocilium = inhibit |
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How are the maculae of utriculus and sacculus structurally and functionally similar?
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Structurally: each is composed of surpporting cells and hair cells; stereocilia and kinocilium extend into endolymph where they are embedded in an otolithic membrane; kinocilium of half the hair cells of each "point" in one direction while the other half point int he opposite direction
Functionally: both provide the brain with constantly updated information about the head's resting position and its rapid, linear movements |
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Otolithic membrane
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gelatinous structure that contains many small crystals of calcium carbonate
crystals add weight to the membrane and enable it to respond to stimuli |
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What are the 2 types of stimuli the crystals of calcium carbonate on the otolithic membrane respond to?
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1. Tilting of the head: gravity pulls on the membrane and bends the ciliary tufts, causing excitation or inhibition depending on the direction of the tilt
2. Rapid linear acceleration or deceleration of the head: when the head moves, inertia delays the movement of the heavy otolithic membrane and that causes it to pull on cilia; forward movement causes backward movement of cilia, and vice versa |
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Crista ampullaris
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is also composed of supporting cells and hair cells whose tufts extend into endolymph
-each rests on a mound of fibrous connective tissue, and have hair cells that contain long stereocilia and kinocilium embedded into a cupula that blocks the semicircular duct |
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Cupula
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gelatinous membrane of the crista ampullaris that does not contain otoliths and therefore has the same approximate weight and specific gravity as the fluid around it - does not respond to gravity, but rather to angular acceleration and deceleration
-gives brain information about head movements |
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Linear head movements vs. angular head movements
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Linear: when head and body move together, movement is detected by maculae
angular: when head moves relative to the rest of the body, movement is detected by the cristae ampullares |
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How does the cristae ampullaris detect angular movement?
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when the head is rotated in the plane of a SCC, inertia causes the endolymph to lag, which pushes on the cupula in the direction opposite of the rotation, and bends the ciliary tufts
-bending of the tufts opens up potassium channels, and activiting them to release neurotransmitters, and ultimately cause nerve impulses in the vestibular division of the VIIIth nerve |
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Which semicircular canals are paired together to detect angular motion?
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-right posterior and left inferior semicircular canals
-left posterior and right inferior canal -2 lateral canals |
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What information is given by the combination of input from all six SCC?
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1. The direction of movement
2. change in movement velocity - acceleration or deceleration that effects the cupula |
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What are the parts of the membranous labyrinth?
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1. cochlear duct
2. sacculus 3. utriculus 4. three SCC 5. endolymphatic sac 6. interconnecting ducts (ductus reuniens, saccular duct, utricular duct, and endolymphatic duct) |
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Proprioception
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helps you sense where you are because you are getting feedback from muscles
involves balance and pressure as well as visual |
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What is the function of the Semicircular canals?
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-kinetic system: motion-based
-senses rotation and acceleration of the head -senses angular accelerations: head sisde to side or up and down -can be stimulated in other ways besides movement |
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What is the function of the otolith organs?
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-static system
-position of head in vertical plane (elevator): based on the pull of gravity; don't have to move -linear forward or sideways motion |
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What are the 2 otolith organs?
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The utricle and the saccule
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What are the 3 vestibular reflexes?
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1. Vestibulo-occular reflex - balance + eyes
2. Vestibulo-collic reflex: balance + neck 3. Vestibulo-spinal: balance + spinal column |
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What is the function of the Vestibulo-occular reflex (VOR)?
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-allows you to turn your head and keep eyes "on the ball"
-can keep steady focus as head turns |
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What is the function of vestibulo-collic reflex?
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-allows your head to rotate in one direction when body rotates in opposite
-head neck movements |
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What is the function of the vestibulo-spinal reflex?
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-allows you to adjust limbs to avoid falling over when leaning over
-arm and leg postural movements |
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What is nystagmus?
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-involuntary movement of eyeballs
-slow component and rapid return jerk -induced in patients to see if vestibular system is good or is the problem -spontaneous in lesions |
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COWS (Cold Opposite Warm Same)
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-caloric testing of vestublar integrity
-put cold or warm water into each ear and lok for eye movements that reflect vestibular activation -cold water causes opposite eye reaction -warm water causes a same-side eye reaction |
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What are the tests of vestibular function (balance)?
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1.ENG
2.Rotation tests 3. CDP |
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What are the test of auditory (hearing) function?
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1. Pure tone audiometry
2. Speech audiometry 3. Acoustic-Reflex 4. Electrocochleography (ECoG) 5. Otoacoustic emissions (OAE) 6. Auditory brainstem response test - VIII nerve test |
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What are the boundaries of the Middle Ear?
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1. Superior (Top): Tegmental
2. Inferior (Bottom): Jugular 3. Anterior (front): Carotid 4.Posterior (back): Mastoid 5.Medial (middle): Labrynthine 6.Lateral (sides): Membranous |
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What is found within the tegmental part of ME? (superior boundary)
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the tegmen tympani
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What is the Tegmen Tympani?
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a thin layer of bone that forms the roof of the tympanic cavity, separating it from the cranial cavity
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What is found within the jugular part of the ME? (inferior boundary)
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the Tympanic plate
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What is the Tympanic plate?
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a curved platelike bone that is part of the temporal bone and forms the floor and anterior wall of the external auditory canal
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What is a platelike bone that forms the floor and anterior wall of the EAM?
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Tympanic Plate
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What are 3 features found within the Carotid?
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-cochleariform process
-septum canalis mascultubori -orifice Eustachian Tube |
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What is the bony angular process that serves as a pulley for the Tensor Tympani?
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Cochleariform process
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Where is the Cochleariform process found?
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within the Coratid part of the ME (anterior boundary)
above the vestibular window |
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What is the thin, horizontal plate of bone forming SCC?
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Septum Canalis Muscultubori
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Where are the 2 Septum Canalis Muscultubori located?
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The upper is smaller for the tensor tympani muscle
The lower is larger for the auditory tube |
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Where does the Septum Canalis Muscultubori end in the ME?
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at the Cochleariform process
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What is located above the floor of the middle ear?
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Orifice Eustachian tube (within Carotid - anterior boundary)
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What is found within the mastoid portion of the ME? (posterior boundary)
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1. Fossa Incudis
2. Aditus to Tympanic Antrum 3. Pyramidal Eminence |
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What is the small depression in the epitympanic recess that lodges the short limb of the Incus?
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Fossa Incudis
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What is the Aditus to Tympanic Antrum?
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leads to the epitympanic recess leading to tympanic antrum
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What is the conical projection below the vestibular window in ME?
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Pyramidal Eminence
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The ______ contains the Stapedius muscle
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Pyramidal Eminence
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What can be found within the labrynthine portion of the ME?
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1. Prominence Facial Canal
2. Oval Window 3. Promonotory 4. Round Window |
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Where the facial nerve is contained
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Prominence Facial Canal
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A membrane-covered opening that contains the Stapes and leads from the ME to the vestibule of the IE?
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Oval Window
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The _______ is the hollow prominence followed by first turn of the cochlea
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Promonotory
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Which opening allows fluid in the cochlea to move, ensuring stimulation of hair cells in the inner ear?
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Round Window
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The _____ closes off the cochlea from the middle ear
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Round Window
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What can be found within the membranous portion of the ME? (lateral boundary)
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1. Tympanic Membrane
2. Chorda Tympani |
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Which membrane separates the EAM from the middle ear?
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Tympanic Membrane
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The Chorda Tympani branches off from which nerve?
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Facial Nerve V
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