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Med Neuro2 Lect6
Med Neuro2 Lect6 Auditory System II
| Question | Answer |
|---|---|
| How do the inner (just inside the inner pilar) and outer (outside the outer pilar) hair cells located on the reticular plate come into contact with the tectorial membrane? | The hair cells are connected to the tectorial membrane via stereocilia that are located on their tips. |
| What structure comes off the spiral lamina? | Tectorial membrane |
| The tips of te hair cells are exposed to ______? while the base of the hair cells are exposed to _______? | 1.Endolymph. 2.Perilymph. |
| What connects the stereocilia to the ion channels on the hair cell membrane? what type of ion channels are they? | Tip-links. **K+ ion channels (the ednolymph has high K+ concentration). |
| What sort of stereocilia movement will open the ion channels? what affects will this have on the hair cell? | Movement RIGHT will open the ion channels by pulling on the tip-links. This will increase the hair cell depolarization, speeding up vesicular release onto CHVIII. |
| Are the hair cell ion channels closed at rest? | NO. they leak K+ into the cell. |
| What sore of stereocilia movement will close the ion channels? what affects will this have on the hair cell? | movement LEFT will close the ion channels. **This will decrease the amount of depolarization & slow vesicle release onto CN VIII. |
| What is responsible for the High concentration of K+ in the endolymph? | Stria Vascularis. Acts as a K+ ion pump into the endolymph from the vasculature. |
| Voltages of the Endo & Peri lymph as well as the hair cell? | 1.Endolymph: +80mV. 2.Perilymph: 0mV. 3.Hair cell: -40-60mV. **this creates a large (100mV) driving force of K+ into the cell. |
| Tract the movement of K+ as it is "recycled" within the cochlea | 1.High potassium in the endolymph. 2.Outer hair cells to support cells. 3.Support cells to fibrocytes. 4.Fibrocytes to stria vascularis. 5.Return to endolymph. |
| What allows the passage of the K+ ions b/w these cells? | Connexins forming gap junctions. **Congenital defects in this will show symptoms in heart and thyroid as well. |
| How can toxins affect hearing? | Toxins can inhibit connexins and thus the movement of K+. **this will destroy the driving gradient of K+ into the cells and thus the vesicle release onto CN VIII. |
| Compare Syndromic Vs non-syndromic deafness. | 1.Syndromic: Problems in the connexins (accounts for 1/3 of congenital hearing loss). 2.Non-syndromic: targets only the cochlea itself (accounts for 2/3 of congenital deafness). **Syndromic will produce heart & thyroid problems as well. |
| Topography of the CN VIII (Cochleotopy) | 1.Outer regions: carry High frequencies back to the brainstem. 2.Centrally: carries low frequencies from the apex back to the brainstem. **indicates an orderly arrangement of fibers based on their position on the basilar membrane |
| Briefly describe how the Prosthesis for hearing works to replace the sensorineural hearing loss. At what age should one be implanted in a child to save their spoken language? | Prosthesis Electrode is threaded thru the round window, along the basilar membrane and is organized via higher and low frequency. **No later than age 10. Want to do it by age 2. |
| Track the pathway of CN VIII back from the cochlea | 1.Cochlear Nucleus (lateral medulla). 2.Superior Olivary Nuclei. 3.Nuclei of the lateral Lemniscus. 4.Lateral lemniscus. 5.Inferior Colliculus (Pons). 6.Medial Geniculate Nuclei (thalamus). 7.Temporal Cortex (Primary auditory cortex) |
| What is the main function of the Inferior Colliculus in this process? | Creates an acoustic map of space. **High freq sound will be found medially. **Low freq sound will be found laterally. |
| Where is the Primary auditory cortex located? How is it organized in terms of topography? | Superior Temporal Gyrus beside the Insula. **Cochleotopic map: High freq are superioposterior, Low freq are inferoanterior. |
| When looking at the Brainstem Auditory evoked potential, Which peak is the most important? What does it represent? | Peak V, which is also the most robust/largest peak. It represents the Inferior Calliculus and thus is an indicator of brainstem activity |
| If everything on a Brainstem Auditory evoked potential is normal until peak V, what does this mean? | There is either a lesion on the superior midbrain or medial Geniculate. |
| When graphing the Auditory brainstem response, which type is the worst (representing sawteeth)? | Type 5. **If the cochlea are intact and the individual has a type 5 wave, they have severe brainstem damage. |
| What could be a cause of type 5 wavs seen on a Auditory brainstem graph, thus having severe brainstem damage | Durret Hemorrhages which come about from pressure in the head forcing the brainstem out the foramen magnum. **this will rupture BV. |
Created by:
WeeG
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