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Old 08-22-2012
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Default What ST segment represents?

A healthy subject has an electrocardiogram recorded as part of a medical physiology laboratory class. The ST segment is at exactly the same vertical position as the PR interval (isoelectric line). In which phase of the action potential are all ventricular muscle cells during the ST segment in this subject?

a) Phase 0
b) Phase 1
c) Phase 2
d) Phase 3
e) Phase 4
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Old 08-23-2012
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i hope it's a)phase 0

nice question
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Old 08-23-2012
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it's phase 2 as it represents ventricualr contraction ( calcium is going in )
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Old 08-23-2012
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Default Phase 2

ya i think its a plateau phase Ca2+ influx and K+ efflux in same amount.
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Old 08-23-2012
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Default correct answer

The answer is c) Phase 2

Phase 2 is the plateau phase, which is of long enough duration that all ventricular cells can be at this potential at the same time, producing no potential on a surface electrocardiogram. This is the ST segment.
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