L7 - Transmission and Saltatory Conduction

Question 1

Electrical and chemical signals?

Answer 1

E: within neurons

C: between neurons

Question 2

Telegraph current attenuation

Answer 2

Current is lost as it flows from source to receiving station → I in > I out

= Vo exp-x/λ - λ is called the length constant

Higher the length constant, the less loss of current there is

37%

Question 3

The transatlantic solution

Answer 3

efficient transmission want cables with big length constants

Length constant depends on Rm (leakiness), Ri (conductivity) and diameter
o Increase Rm Better Insulation
o Decrease Ri Better conducting cores
o Increase d Fatter cables

Question 4

Attenuation in dendrites

Answer 4

Not a big problem because:
o Short distances involved
o Many inputs (big starting signal)

Dendrites can generate action potentials. But…
passive and not involve a wave of action potentials

Question 5

Why don’t axons have attenuation?

Answer 5

Far higher density of sodium channels than dendrites

AP wave

Increase Rm Better Insulation
Increase d Fatter cables