Frog nerve experiment and theory

Question 1

What are the factors that determine amplitude and duration of a CAP?

Answer 1

Axon recruitment

Conduction velocity

Question 2

What are the factors that influence conduction velocity?

Answer 2

Diameter of axons
Membrane resistance and membrane capacitance
Whether it is myelinated or not

Question 3

How do you calculate the conduction velocity from this experiment?

Answer 3

Plot a graph of distance against time for both the onset of the CAP and the peak. Work out the gradient of time/distance and then due the reciprocal of that

Question 4

What is the difference between relative and absolute refractory period for a CAP

Answer 4

Absolute refractory period is when there is no excitability even if the stimulus intensity increases
Relative refractory period is when the inactivated sodium channels start to recover and there is the start of an CAP when the stimulus intensity is high enough

Question 5

What is the difference between monophasic and diaphasic and how can it be achieved experimentally?

Answer 5

Monophasic CAP have just one dumbell shape. Diaphasic has a positive and negative

Question 6

What causes a stimulus artefact?

Answer 6

A brief biphasic deflection at the beginning which results from virtually instantaneous, passive current spread from stimulating electrodes to recording electrodes.