During embryonic development, neurons may acquire their characteristic excitabilitjes

During embryonic development, neurons may acquire their characteristic excitabilitjes over some period of time. Different types of channels may appear at different times as the neurons approach maturity. The data below were collected for some large spinal cord neurons in the frog, Xenopus, at different times after development began. For each stage described below, list what types of channels must be present to account for the data given for each stage a. Stage 18 (19 hrs after fertilization): Resting potentials were around —80mV, but no action potentials could be elicited b. Stage 20 (22 hrs after fertilization): Depolarizing pulses applied to the neurons produced prolonged (up to 1100msec!) action potentials, followed by an after hyperpolarization. Removing external Na+ or external (31′ has no effect on this response. TTX also has no effect. The peak of the action potential varied according to the Nernst equation for Ca+2 and could be blocked by the divalent cation Co? TEA substantially prolonged the response and reduced the after hyperpolarization