Experiment Three: Effect of Temperature on Neurons

Ion channels transport Na+ and K+ across neural membrane

Action potentials (“spikes”) are generated by sodium ion (Na+) infusion depolarizing the cell membrane and potassium ion (K+) expulsion repolarizing it.

Ion channels will not open if temperature too low

Ion channels and nerve membranes come apart if

temperature too high

Procedures: Put the cockroach in a jar of ice water

Procedures: Cut off one of roach’s legs near the body

(Put petroleum jelly on exposed wound on body and leg, return cockroach to house, leg will grow back if cockroach not full grown adult)

Procedures: Place leg on cork of SpiderBox, with a bit of leg

overhang

Procedures: Put one electrode in the femur and the other in the

coxa

Exercise 1: Cool the preparation and identify temperature at which

neural spikes go away

You can also use a cooler of dry ice

Note that active refridgerators can be very electrically noisy

though..you may want to unplug the

cold freezer

Exercise 2: Heat system and identify temperature at which all neurons discharge

Tabulate heat and cold limits for different legs of different species