chronoscope microswitch?

0I am reading a geratric documnet, and there are some words and phrases which I don't understand. Could you please help me?02br
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00-Chronoscope microswitch?02br
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00-the belly of the muscle?02br
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00These words are in this sentence:"If EEG electrodes are placed on the scalp overlying the celebral visual cortex (for a visual stimulus) and motor cortex of the brain and an EMG electrodes is placed over the 01u00belly of the muscle02u00 to be used, the combination of records from the electrodes and the 01u00chronoscope microswitches02u00 (or computer keys) provides a more detailed analysis of the response"02br
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00-activate the movement time switch? 02br
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00' passing the wrist through the beam emitted by the diode 01u00activates the movement time switch02u00, causing an offset of the total response time trace on the oscilloscope'02br
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00-' general' in these sentence is 'general' like in the phrase 'in general' or mean ' the whole body'?02br
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00'Simple reaction time is thought to represent the 01u00general02u00 responsiveness of the central nervous system and has been described as ' a 01u00general primary02u00 response mechanism of the CNS". 'in addition to the 01u00general02u00 responsivity(speed) of the CNS, another indicator of neurological inegrity is variability of performance".02br
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00By the way, could you please tell me what does the second sentence mean?02br
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00-what are the differences between ' median reaction time' and' average reaction time"?02br
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00- what does ' first- order regression lines' mean?02br
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00' Mean of median auditory reaction times for each participant as a function of age, gender and task types expressed with standard error bars, spline fitting, and01u00 first-order regression02u00 lines?"02br
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00- ' variability' refers to the differences among people's performances or among one person's performances in different periods of time?02br
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00thank you for your time and consideration.0-