Neuroscience 5 - Electromyography

Question 1

What is electromyography?

Answer 1

• Recording of the action potentials occurring in skeletal muscle fibres
• Extra-cellular recording: both electrodes outside the muscle fibres.

Question 2

Give some other examples of extracellular recordings.

Answer 2

• 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.

Question 3

Whats the difference between an extracellular recording and an intracellular recording?

Answer 3

• Intracellular recordings, one electrode is inside the cell and one is outside, measuring the voltage between inside and outside the cell.
• In extracellular recordings, both electrodes are outside the muscle fibres, measuring the voltage between two sites. Looks at the impulse propagation.

Question 4

Define twitch

Answer 4

• A short sudden movement of the muscle, which is involuntary.
• Generated by the stimulus of a nerve

Question 5

Define tetanus in relation to nerves

Answer 5

• Tetanic contractions are fused contractions, which last as long as the stimulus lasts
• This can be voluntary or involuntary, by electrical stimulation at a high enough frequency (20stim/s)

Question 6

Define summation in regards to nerves

Answer 6

• Summation is where an electrical impulse occurs before the previous effect has ended.
• This results in a larger response occuring.