Electromyography

Question 1

What is an EMG?

Answer 1

a recording of the action potentials occurring in skeletal muscle fibres

Mayo Clinic: a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons).

Question 2

What are the 2 ways to measure EMG and which way is usually used in clinical practice?

Answer 2

• extracellularly - electrodes are placed on the top of the muscle fibres (on the skin). Record the emf/potential between the 2 locations both outside the cells
  used in clinical practice
• intracellularly - uses a needle in the skin and compares the inside and the outside of the skin
  used in labs - not clinically used

Question 3

what are the other extracellular recordings of action potentials that can be done in the body?

Answer 3

ECG - electrocardiogram - electrodes on the limbs and chest. Records APs of the heart
EEG - electroencephalogram - electrons on the scalp recording APs of the brain

Question 4

Describe what would be seen on an ECG at rest

Answer 4

no difference between the 2 electrodes

Question 5

Describe what would be seen on an ECG when an action potential is simulated

Answer 5

• as it reaches 1st electrode, a difference will be seen
• in between the 2 electrodes, no differnce will be seen (line will be isoelectric)
• as the AP reaches the 2nd electrode, there is a difference that is equal but opposite in polarity to the change in the first electrode