Question

To complete the model, we need values for these resistances. There are actually many ion channels passing through the membrane, so our model circuit needs to be constructed using the resistance of a single segment of membrane rather than a single ion channel. Each segment of membrane consists of many such ion channels in parallel, but the average resistivity of the membrane can be measured and used to find the resistance of a segment of membrane. Use the relationship between resistance, resistivity, length, and cross-sectional area to estimate values of resistance of a membrane segment Rmem and an axoplasm segment, Raxon, using the following order-of-magnitude values. (Hint: Think about the geometry of the axon and the membrane): • the diameter of the axon ∼10 μm • the average resistivity of the membrane ∼ 108 Ω·m • the membrane thickness ∼10 nm • the segment length ∼1 mm • the resistivity of the axoplasm ∼1 Ω·m

Answer 1