Nodes of Ranvier are regularly spaced interruptions of the myelin sheath along an axon. An oligodendrocyte is a class of glial cells that wrap axons in the CNS, forming myelin sheaths. To get single channel recordings, you must patch clamp.
Intracellular recording is the most appropriate answer.
As stated in the lecture material, Sakman and Neher received the Nobel Prize for the work developing patch clamp recording and single ion channel recording. This question if from 338 lab on neurosim. The whole graph represents the Nernst equation. Therefore, the slope is the constant. More specifically, it is 58.