The Oval Window Is Connected Directly To Which Passageway?

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Session 137

Last week we took a quick break from passages with detached questions. This week nosotros look at Passage 3 that covers the pathway in which we hear with the ear.

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[01:42] Passage iii

Deflection of the tympanic membrane transfers vibrations to the ossicles, whose function is to dilate the vibration pressure level delivered to the oval window, a minor hole in the cochlea. Without this distension, it is estimated that all but 0.1% of the incoming audio energy would be reflected upon contact with the cochlear fluid.

Inner hair cells are the mechanotransduction cells responsible for converting the basilar membrane move into auditory information. Figure ii shows their signal transmission pathway, The hair cells depend on stereocilia, microtubule-based projections. The tips of neighboring stereocilia are connected via actin-based linkages, and basilar membrane motility can either strain or relax the tensions of these linkages. When strained, the linkages actuate not-specific cation channels, which causes an influx of ions that depolarize the hair jail cell. As a consequence of the depolarization, voltage-gated calcium channels are opened, which after causes the package and release of neurotransmitters into the synaptic cleft. The synapse connects the inner hair cell to screw ganglion cells, which in plow connect to the auditory nerve that relays the information to our encephalon for further processing.

[04:23] Question 14

In order to amplify the pressure exerted on the cochlear fluid at the oval window, the oval window must be:

(A) larger than the tympanic membrane.

(B) smaller than the tympanic membrane.

(D) less rigid than the tympanic membrane.

Clara's insights:

The correct answer hither is B. There are a couple of ways y'all can solve this. This involves a little bit of understanding of physics. It'due south this idea that if you're going to exert the same forcefulness or pressure, where the force per unit area is equal to strength over area, the way to amplify that force per unit area is to exert over a really minor area.

Some other way to distinguish this is that the passage defines the oval window every bit the small hole in the cochlea.

[07:16] Question fifteen

Which of the following bones has a footplate that acts as a piston, making contact with the cochlear fluid at the oval window?

Scaphoid
Malleus
Capitate
Stapes

Clara'south insights:

The right answer is D. The A and C are bones in the wrist. If y'all see a give-and-take and not familiar with information technology, it's probably not something you lot should option. The Stapes is the last bone of the three and it directly makes contact with the cochlear fluid.

[08:50] Question 17

The stereocilia of inner ear cells projection into the endolymph fluid, where in that location is a high Thousand+ and Cl- content but a low Na+ content. Based on this data and the information in the passage, which of the following ions would contribute most to the depolarization of the cell if the tip links between stereocilia were strained?

1000+
Na+
CL-

(A) I only

(B) 2 just

(D) I and 3 only

Clara's insights:

The correct answer hither is A. Cl and Na are coming in considering where all the stuff is potentially merely they're anions.

[12:10] Question xviii

Which of the post-obit is most likely the excitatory neurotransmitter released into the synaptic cleft betwixt the inner ear pilus cells and the spiral ganglion?

(A) GABA

(B) Acetylcholine

(D) Glutamate

Clara'due south insights:

The correct reply here is D since they say excitatory neurotransmitter. And GABA is the classic inhibitory neurotransmitter and glutamate is the excitatory one. Serotonin is brain-focused and only comes up on the MCAT in terms of advantage pathway and depression. Acetylcholine is the classically involved with muscle contraction.

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