6 EMG Flashcards
Q: What is an EMG? What does it measure?
A: electromyogram
electrodiagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles
- recording of the action potentials occurring in skeletal muscle fibres
Q: Apart from EMG, give 2 other examples of extra cellular recordings. Include where the electrodes are placed.
A: ECG (EKG), electrocardiogram, recording action potentials from the heart. Electrodes on limbs, or chest.
EEG, electroencephalogram, recording action potentials from the brain. Electrodes on the scalp.
Q: What is an intracellular recording? Where are the electrodes? How does an extracellular recording compare?
A: one electrode inside the cell
Measure emf between inside and outside cell
both electrodes outside the muscle fibres-on membrane. Record the emf (potential) between 2 locations both outside the cells/fibres
Q: Draw a diagram that shows an example extracellular recording between 2 sites outside the fibres.
A: REFER
Q: Where do you place the electrodes to get ulnar nerve stimulation? (2)
A: fleshy pad of palm and below where you take radial pulse
Q: Draw a graph that shows gradually increasing then decreasing voluntary contraction. How is this conducted?
A: REFER. EMG line and force line
attach thumb to something that records force
person is asked to push something harder and harder then relax
result is increasing AP in muscle = more force applied
Q: Draw an EMG and twitch force graph for a stimulus of 3mA.
A: TF= -3 flat line
EMG= 0 with a single small line down twitch known as an artefact
Q: What causes an artefact? What is a delay on an EMG graph caused by?
A: interference between stimulating equipment and recording equipment
in relation to how far stimulus is from recording and how quickly nerve conducts
Q: Draw an EMG and twitch force graph for a stimulus of 5mA.
A: REFER
EMG= tiny delay then up down and flat line
TF= flat line at -3 but increases a little after EMG peak
Q: Draw an EMG and twitch force graph for a stimulus of 7mA.
A: REFER
EMG= tiny delay then up down and flat line (larger than 5mA and 2 of them in quick succession)
TF= flat line at -3 but increases a little after EMG peak (larger than at 5mA)
Q: Draw an EMG and twitch force graph for a stimulus of 9mA.
A: REFER
EMG= tiny delay then down up and flat line (larger than 7mA)
TF= flat line at -3 but increases a little after EMG peak (larger than at 7mA)
Q: Draw an EMG and twitch force graph for electrical stimulations (constant stimulus strength) at a frequency of 1/s.
A: REFER
Q: What happens when give a constant stimulation for a prolonged period? (2)
A: can cause pain
can cause tetanus
Q: Draw an EMG and twitch force graph for electrical stimulations (constant stimulus strength) at a frequency of 5/s.
A: REFER
5/s= 5 twitches of same size and close together
Q: Draw an EMG and twitch force graph for electrical stimulations (constant stimulus strength) at a frequency of 10/s.
A: REFER
10/s= frequency where muscle can’t relax between= summation
