Lab 6 - Bio 319 Dr. Cohn Exam with
Complete Solutions
What does EMG stand for? - ANS-Electromyogram
What is a EMG? - ANS-it is a technique that measures the electrical activity of the
MUSCLES and the NERVES controlling the muscles
What are two methods used for recording? - ANS-needle electrodes and electrodes
places on the skin surface
What does size and shape of the waveform measured provide information of? - ANS-
about how the muscles respond when the nerves are stimulated
In a clinical setting, what are EMG most often used for? - ANS-when people have
symptoms of weakness, and can detect neurological disorders
Motor units fire asynchronously or synchronously? - ANS-asynchronously
What happens as the muscle strength increases? - ANS-the density of action potentials
increase, meaning the signal represents the electrical activity of thousands of individual
muscle fibers
What makes about 70% of the cell body mass? - ANS-skeletal muscle cells
What are upper motor neuron lesions, what is a consequence of this? - ANS-strokes
damaging neurons in the brain causing loss of muscle function
What is a twitch? - ANS-a brief contraction caused by ATP
What is recruitment? - ANS-controlling the number of twitches by adjusting the number
of motor axons firing
What is another way that the nervous system controls muscle contraction? - ANS-by
adjusting the number of action potentials
What is the stimulation interval that would cause separate twitches? - ANS-greater than
200 ms
What interval would cause summation? - ANS-200-75ms
