Cable Properties (FINAL)

Question 1

What are the 2 main cable properties?

Answer 1

Membrane resistance (R_m)
Internal (axial) resistance (R_i)

Question 2

How does high membrane resistance lead to faster conduction velocity?

Answer 2

High resistance = less current leakage = signal stays stronger & spreads farther

Question 3

How does low internal resistance lead to faster conduction velocity?

Answer 3

Low internal resistance = current moves inside easily = signal spreads faster

Question 4

Give the formula for time constant 𝜏, and explain variables.

Answer 4

𝜏 = RC

R = resistance
C = capacitance

Question 5

What does the time constant 𝜏 tell us?

Answer 5

The time in seconds for voltage across capacitor to reach 63.2%

Question 6

Give the formula for the length constant λ, and explain the variables.

Answer 6

λ = ((r_m)/(r_i + r_o))^1/2

r_m = membrane resistance
r_i = internal resistance
r_o = total resistance in external loop of nerve fiber (negligible, so zero)