4/13/15 April 8, 2015 H&H cont Snail 1 Lab Results due - PDF document

4/13/15 April 8, 2015 H&H cont Snail 1 Lab Results due tomorrow See data folders in Dropbox Voltage clamp of squid giant axon Alan Hodgkin Andrew Huxley Sammy Squid Prize motivation: "for their discoveries concerning the ionic mechanisms involved in excitation of the nerve cell membrane" Determining reversal potential for K from tail current Determining reversal potential for K from tail current Already showed in this paper 1) Na responsible for depolarizing current of AP ICa Tail 2) Separated I in and I out example 2) Calculated I Na and I out time course and conductance -50 ICa Tail How did they example I Ca find K Nernst Pot for conductance -50 calculations? EPSC I Ca EPSC 1

4/13/15 Conductance rate of rise/voltage relationship Conductance/Voltage relationship I Na I Na Depolarization RP = -55 mV Depolarization RP = -55 mV I K I K Depolarization Depolarization What did they do in the first paper?? 1) Showed that Na + is the inward charge carrier for the AP. 2) Separated I Na and I k . 3) Expressed the currents in terms of conductance. 4) Applied this to calculations of the time course of g Na and g K . 5) Suggested the importance of these currents for the AP. “Share the prize!” Voltage clamp of squid giant axon 2

4/13/15 Changing conditioning pulse time- depolarizing duration This paper was concerned with: 1) Providing some quantitative evidence about 0 = -55 mV the influence of membrane potential on the process responsible for inactivation. Pre-pulse > 20 ms, 40% 2) Quantifying the rate at which repolarization restores reduction of I in the ability of the membrane to respond with its characteristic increase in Na + permeability. I Na Changing conditioning pulse time- hyperpolarizing duration Inactivation and recovery exponential Reached steady state 0 = -55 mV Faster at larger V steps I in inactivation at rest! 0 = -55 mV 3

4/13/15 Changing conditioning pulse amplitude h infinity curve h = ability of membrane to undergo a change in Na permeability Time is constant, pre-step is changed 40% inactivation at rest! 0 = -55 mV depolarize hyperpolarize 0 = -55 mV Activation/ inactivation parameters inactivation curve activation curve What is the state of the Na channel? 4