Wednesday, June 24, 2009

squid nerve response

04.03.09. Nerves were first studied in squids, because squids have very large nerve cells (a squid's giant axon--a single nerve cell--can be millimeters thick and centimeters long). Students watched this excerpt from the film "The Squid and its Giant Nerve Fiber" (also posted here as part of a neurophysiology course at Smith College) showing the removal and activation of a squid's giant axon. As seen at minute 2:24, the axon experiences a sharp rise in voltage, then a fall, and finally a return to the original level. This voltage pattern is transmitted down the length of the nerve each time it "fires." Students were presented with a candidate mathematical model for voltage V (in millivolts) as a function of time t (in seconds), which, upon combining like terms, they simplified to V = t^3 - 15*t^2 + 50*t. Students then checked the legitimacy of the model by generating their own data points from the equation and plotting the curve. Upon comparing with the experiment in the video, it is evident that the model breaks down at large negative and positive values of t.