exam 2 2010 II

3 在黑暗中，有關視網膜錐形細胞的敘述，下列何者錯誤？

Guanosine monophosphate（GMP）濃度上升 Influx of calcium

細胞處於去極化狀態（depolarized state） Outer segment膜上的鈣離子通道處於開啟狀態

answer is A

if dont know the answer: look at the answers: B and D are pertaining to Ca influx. Ca is positive ion thus c is also correct. influx positive ion result in depolarization

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4 正常人體能感受環境溫度變化，以便做適度的因應。下列有關thermoreceptor的敘述何者錯誤？

Thermoreceptor可分為cold receptor與warm receptor兩種

大部分的warm receptor fiber屬於C fiber

Cold receptor及warm receptor均屬於slowly adapting receptors

受到高於45℃的溫度刺激時，warm receptors興奮性增加，warm fibers的動作電位頻率大增，此時warm receptors可同時偵測痛覺

ansewr D

Thermal

Thermal nociceptors are activated by noxious heat or cold at various temperatures. There are specific nociceptor transducers that are responsible for how and if the specific nerve ending responds to the thermal stimulus. The first to be discovered was TRPV1, and it has a threshold that coincides with the heat pain temperature of 42°C. Other temperature in the warm-hot range is mediated by more than one TRP channel. Each of these channels express a particular C-terminal domain that corresponds to the warm-hot sensitivity. The interactions between all these channels and how the temperature level is determined to be above the pain threshold are unknown at this time. The cool stimuli are sensed by TRPM8 channels. Its C-terminal domain differs from the heat sensitive TRPs. Although this channel corresponds to cool stimuli, it is still unknown whether it also contributes in the detection of intense cold. An interesting finding related to cold stimuli is that tactile sensibility and motor function deteriorate while pain perception persists.

42 is the threshold!!!!

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5 下列有關近視（myopia）的敘述何者正確？

 遠方物體的影像聚焦於視網膜（retina）的前方

可用凸透鏡片（convex lens）協助矯正視力

水晶體（lens）對近距離影像的調節（accommodation）有缺陷

近視患者不會罹患老花眼（presbyopia）

answer is A:

Eye care professionals most commonly correct myopia through the use of corrective lenses, such as glassesor contact lenses. It may also be corrected by refractive surgery, but this does have many risks and side effects. The corrective lenses have a negative optical power (i.e. are concave) which compensates for the excessive positive diopters of the myopic eye.

just have to remember : lens increase positive power thus you need a concave (negative power lense) to bring the image to retina.

image falls on the front of retina in myopia.

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