Hearing and Balance Flashcards
How does sound travel through the auditory system?
sound waves enter the outer ear –> tympanic membrane –> ossicles (malleus, stapes, incus) –> oval windown –> scala vestibuli –> helicotrema –> scala tympani –> cause a change in the mechanoR hair cells –> activate nerve terminal from spiral ganglia –> CNS via CN VIII
How are the hair cells activated?
Deformation of the basilar membrane activates the hair cells within the cochlear duct –> activated
Hair cells have microvili + one large vili = Kinocillium (if present)
Deformation TOWARDS the largest = activates the mechanoR cell –> activating the nerve terminals
What type of infomation can the hair cell transmit (3), via what unique feature?
Displacement of the basilar membrane stimmulate iner hair cells by deflecting their sterocilliary bundles by motion of hte liquid beneath the tectorial membrane –>
INNER Hair cell can transmit info regarding FREQUENCY, INTENSITY AND TIMING info to the spiral ganglion becuase of the unique morphology of the RIBBON SYNAPSE
OUTER hair cells enhance the responsiveness of INNER hair cells (ACTIVE PROCESS) and their stereocilliary attach to the tectorial membrane
Inner hair cells are essential for _____
Outer hair cells are essential for _____
Inner –> hearing
Outer –> amplificaiton of sound or frequency selection
Otoliths are structures within the ____ and the ______
Serve to detect ______ motion of the head
Provides our ability to sense ______, such as _____.
Otoliths are stuctures within the UTRICLE and the SACCULE
Seve to detect LINEAR MOTION of the head
Provides our ability to sense which way is up or down, ie- gravity
Canals serve to detect ______ motion of the head
canals serve to detect ANGULAR motion of the head
Nystagums is _________ movements of the eye
_____ generates the slow phase, helping keep the eye on target
Nystagums = rhythmic back and forth movement of the eye
Usually the movement is slow in one direction “smooth” and fast “saccadic” in the other
when you spin, the VOR is gnerating the slow phase – helps to keep an eye on a target. Once the eye approaches the maxium it can turn –> saccade, moving the eye in opposite direction and onto new target (optokinetic nystagmus or OKN)
What are 3 ways in which we get dizzy?
- Vestibular input without vision (ie- spinning in a chair with your eyes closed –> constant motion eventually results in the cupula membrane returning to its baseline, and you suddenly open your eyes)
- Sense of motion via the visual system but without vestibular “confirmation” (ie- looking out a car window when an adjacet car moves away – false sense of motion)
- Sense of motion via the vestibular sytem, but without visual confirmation (a disconnect, ie) in a cabin of a boat during a storm – motion sickness)
What is the main function of the vestibulo-ocular reflex (VOR)?
VOR stablizes the image on the same part of the retina during a rotation of the head
As the head rotates, VOR rotates the eyes with teh same speed but in the opposite direction
Without VOR, the image would appear “smeared” across the retina
“stabilization” occurs via the NUCLEUS PREPOSITUS HYPOGLOSSI
The lateral vestibulospinal tract
maintains ____ by acting on the ____
Starts at: ________, travels ________ to the ______ of the spinal cord until the __________.
The lateral vestibulospinal tract maintains BALANCE by acting on the PROXIMAL LIMB MUSCLES.
Starts at the LATERAL VESTIBULAR NUCLEUS, travels the ENTIRE LENGTH of the spinal cord until the VENTRAL FUNICULUS.
The function of the Medial Vestibulospinal Tract (descending MLF) is to maintain the __________ by working on ______.
From the ___________ to the ________ of the spinal cord, until the ____________.
The function of the Medial Vestibulospinal Tract is to maintain the head erect by acting on neck muscles.
From the medial vestibular nucleus up to the cervical spinal cord only, until the medial ventral funiculus
