do all nerve fibres in the sciatic nerve conduct action potentials at the same rate?

I have read 2 different things and now im not sure which is true. 1. the action potential occurs at the same rate as the kinetic energy from one nerve is transfered onto the next nerve. 2. action potentials differ between nerve fibres as the thresholds are different in each nerve (because of the excitability [...] http://bit.ly/qlBbOM