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The Length Constant

by Greg Crowther


This song was written for Biology 351 at UW-Bothell. It helps students understand the passive spread of electrical signals through neurons.


The length constant, sometimes called lambda
(Another word spelled with L)
Is a root of a ratio of resistances.
Which resistances? I will tell....

Rm over Ri!
Rm over Ri!
Which way is easier for the ions to fly?
Rm over Ri!

Other Files

MP3 (demo)

music video

sheet music (with melody play-back)

Lesson Plan

Songs like this one can be used during class meetings and/or in homework assignments. Either way, the song will be most impactful if students DO something with it, as opposed to just listening.

An initial, simple follow-up activity could be to answer the study questions below. A more extensive interaction with the song might entail (A) learning to sing it, using an audio file and/or sheet music as a guide, and/or (B) illustrating it with pictures, bodily poses, and/or bodily movements. The latter activity could begin with students identifying the most important or most challenging content of the song, and deciding how to illustrate that particular content.

Study Questions

(1) What do Rm and Ri stand for?

(2) How do (a) myelin and (b) axon diameter affect Rm and/or Ri?

(3) The song refers to "a root of a ratio of resistances." What is that?

(4) What units does the length constant have?

(5) The length constant is a distance or length. What is the meaning of this distance? That is, what happens over this distance?

(6) To which parts of neurons does this equation apply?

(7) Considering the specific content covered by this song, is there anything important that is missing, unclear, or misleading? If so, what?

(Answers may be found on the answers page.)