Lecture 2b- Basic electrical nerve stimulation

Question 1

What does Ohms Law state

Answer 1

V = iR,

R = resistance
i = ionic current).

Question 2

How is current applied

and whats the pulse number

Answer 2

via surface or needle electrodes in pulses of ~ 100 µse

Question 3

How much current is needed to stimulate through the skin

Answer 3

At least 20 mA is needed to stimulate through the skin

This requires up to 250 volts because dry skin has high electrical resistance – as governed by Ohm’s law (V = iR, where R = resistance, and i = ionic current)

Question 4

What has dry skin got

Answer 4

High electrical resistance

Question 5

What electrodes are used for superficial nerves

Answer 5

Surface electrodes are used to stimulate and record from superficial nerves

Question 6

What is latency

Answer 6

Total time from stimulation to an observed muscle twitch

Question 7

What is the process of latency

Answer 7

Latency includes the transit time across neuromuscular junction (NMJ)

Question 8

The NMJ is a chemical synapse that relies on……

Answer 8

diffusion of neurotransmitter (which is a slower process than electrical conduction)

Question 9

What electrodes are used for deeper nerves

Answer 9

needle electrodes

Question 10

Why must you stimulate two positions and measure at one

Answer 10

to get true motor nerve conduction velocity

(hence, both proximal and distal stimulation points, as illustrated in Figure 2.8C).