Term
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Definition
| -MISO (O for oval window) |
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Term
| Where do we find perilymph and endolymph? What is the difference? |
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Definition
-Endolymph has the composition of intracellular fluid (high K+), and perilymph is like any normal extracellular fluid
-Endolymph is inside the cochlear duct, semicircular ducts, etc., and baths the hair cells |
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Term
| What is the pathway for sound waves through the cochlear duct? What is in between the two pathways? |
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Definition
-Scala vestibuli on the way in, scala tympani on the way out
-The scala media (endolymph) is between the two |
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Term
| What are the ganglia for hearing? |
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Definition
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Term
| What is the transmission signal for hearing? |
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Definition
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Term
| What is the anatomy of the organ of corti? How are different frequencies sensed? |
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Definition
-The *basilar membrane vibrates more towards its termination (end of cochlea) for lower frequencies
http://www.d.umn.edu/~jfitzake/Lectures/UndergradPharmacy/SensoryPhysiology/Audition/Figures/OrganOfCorti.gif |
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Term
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Definition
-Age related hearing loss that results as a loss of hair cells at the base of the cochlea
-Results in difficulty hearing higher frequencies
-(Defense mechanism for dealing with nagging wives?) |
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Term
| How many neurons in the pathway for sound? |
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Definition
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Term
| What is the pathway? Where is binaural input first received? |
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Definition
| Left spiral gang.-->left ventral and dorsal cochlear nuclei (in pontomedular junction)-->**right & left superior olivary nuclei (pons)-->continues as **medial lemniscus-->inferior colliculus (midbrain)-->medial geniculate body (MGB in thalamus)-->superior temporal gyrus |
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Term
| What's the Brodmann area? |
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Definition
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Term
| What is in the medial lemniscus? What is it connecting again? |
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Definition
-Input from both ears, but mostly contra
-Connects the SON to the inferior colliculus |
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Term
| Where do the pathways cross? |
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Definition
-The trapezoid body between the superior olivary nuclei
-These are actually able to analyze sound for localization
-No crossing after the SONs |
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Term
| What will we get if we lesion after the SONs? |
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Definition
| -Slight bilateral loss of hearing and decreased localization |
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Term
| What important structure does the adjacent association auditory cortex communicate with? |
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Definition
| -Wernicke's area; for comprehension of language |
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Term
| Where are the two kinds of sensory receptors in the vestibular system and what do they do? |
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Definition
-One kind is in the semicircular ducts and senses rotation
-The other is in the utricle and saccule for linear acc.
-Nice pic of whole thing; http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%204%20Review/15-27_Labyrinth.JPG |
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Term
| What contains the hair cells of the utricle and saccule? |
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Definition
| -Have patch of hair cells on macula |
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Term
| Where do the primary vestibular fibers go? |
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Definition
| -They go to the four vestibular nuclei in the rostral medulla along with fibers to the flocculonodular lobe of the cerebellum |
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Term
| From the vestibular nuclei, then where to? |
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Definition
| -The secondary vestibular fibers then go to the various motor nuclei for cranial nerves involved in eye movement (III, IV, & VI) for conjugate eye movements |
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Term
| So when turning the head to the right, what all is stimulated? |
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Definition
-The right side horizontal semicircular duct afferents are stimulated (via hair cells), and they in turn would go to the left abducens nucleus and the right occulomotor nucleus
-The net effect is that both eyes look left
-Note that the green paths are being stimulated; http://upload.wikimedia.org/wikipedia/commons/5/58/Simple_vestibulo-ocular_reflex.PNG |
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Term
| Which motor nucleus comes first in the path to the eye? Stipulate which is contralateral to the start of the afferent stimuli? |
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Definition
-VI comes before III and it is "wired" in a series
-The VI nucleus stimulated is contralateral (turing right, we want left eye abducted)
-This means that the path zig zags from right ear, to left VI, to right III |
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Term
| What is the pathway that connects contra VI and III to produce this coordination? |
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Definition
| -The medial longitudinal fasciculus (MLF) |
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Term
| So what would we expect in a vestibular lesion? |
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Definition
| -Slow deviation of both eyes toward the side of the lesion followed by a fast correction away |
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Term
| What is a disease involved with vertigo caused by vestibular involvement? |
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Definition
-Ménière's disease
-Causes abrupt recurrent vertigo attacks followed by tinnitus or deafness, and usually only in one ear
-Caused by distention of fluid filled spaces (absorption, circulation, or other problems)
-Most often in middle age |
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Term
| What is the fast correction called? To which side does it occur? How can we test it and why? |
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Definition
-Nystagmus
-Always towards stimulated side (away from lesion)
-Can put warm water in the ear and observe nystagmus towards that ear (it is stimulating; cold is the opposite)
-To remember; COWS
-Called the caloric test
-Used to test brain stem function especially in comatose patients |
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Term
| What is the pathway for horizontal conjugate gaze? Stipulate whether each is contra. or ipsi. to gaze? |
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Definition
Frontal eye fields (cortex area 8) [contra]-->
Paramedian pontine reticular formation (PPRF) [ipsi]-->
Abducens nuc. (in PPRF)-->
Occulomotor nuc. [contra]-->
Both nuclei to muscles
http://1.bp.blogspot.com/-lnysLuMoj6M/Trlya-w6rUI/AAAAAAAAEFM/By2siExgihw/s640/voulantary+horizontal+conjugate+gaze.png |
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Term
| So how many neurons are there for movement of the eye? Where are the cell bodies for each path? |
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Definition
-3/4 for both the cochlear reflex and horizontal gaze
-Horizontal gaze vs. cochlear conjugation;
Cerebral cortex = Vestibular ganglia
PPRF = Vestibular nuclei
Abducens (-->muscle and VI)
Occulomotor |
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Term
| So what if we lesion the MLF on the right? |
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Definition
-The medial longitudinal fasciculus carries all fibers due to occulomotor for medial rotation of the ipsilateral eye
-Thus, the **right eye cannot look left
-If we cut both sides, niether eye could look medially |
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Term
| What if we lesion the left frontal eye field in the cortex? |
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Definition
-Then *neither eye will be able to look *right
-Also, both eyes will continually drift left
-Frontal cortex controls contralateral gaze bilaterally |
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Term
| What about if we lesion the PPRF or abducens nucleus? |
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Definition
-Pretty much the same thing as a cortex lesion, except now on the **ipsilateral gaze will be paralyzed (lesion on left can't look left)
-Still get drifting (contra this time) |
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Term
| Quick note on MLF lesions and nystagmus; |
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Definition
-If we lesion the MLF, the eyes are able to look in two different places like a chameleon
-Somehow though, even with a complete MLF lesion, when the eyes are split nystagmus kicks in to jerk the abducted eye back to center (somewhat)
-Essentially there must be some other way to get med. rotation to the eye other than the MLF, but oh well |
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