Welcome to Bioc 415

Course activities

On-line resources

Introductory lab manual (Bioc 211)
Bioc 311 resources

Bioc 415 manual (pdf)

Bioc 415 appendixes (pdf)

Experimental Physiology: Membrane Potential Labs

Pre-lab discussion (Monday 29 Aug – 1 pm ABL 329)

  • Equilibrium potential model for the resting membrane potential and the Nernst equation
  • Sodium pump, ion gradients, and electrogenic property of the pump
  • Suggestions for conducting experiments and collecting data
  • Lab rules – using microelectrodes and tip holders

Laboratory to follow the discussion (GRB W112)

  • Denonstration – crayfish deep extensor preparation and recording membrane potentials
  • Obtain sufficient Em measurements to establish extensor muscle resting potential in normal crayfish saline
  • Obtain sufficient Em measurements to establish resting potential in the absence of sodium pump activity
  • Perform control Em measurements if necessary

Preparation for next time

  • Organize your data and send to instructor via email attachment
  • Conduct a preliminary analysis of the ouabain experiment and be prepared to discuss your findings
  • Complete the posted homework assignment (optional for students who have completed BIOC 385)
  • Read the remainder of chapter 1, origin of the membrane potential
  • [ASSIGNMENT] Prepare an experimental design with which to study the influence of extracellular potassium and sodium ion concentration on the membrane potential; include predictions using the Nernst equation to calculate the membrane potential for variable potassium solutions
  • Be prepared to predict the direction in which potassium or sodium ion will move in response to a solutiion change
  • Be prepared to predict the probable effect of changing extracellular potassium or sodium on Em
  • Be prepared fora possible quiz on the reading, subject matter covered today, preliminary data analysis, and/or predicted ion movements, effects on the membrane potential

Pre-lab discussion (Wednesday 31 Aug – 2:15 pm GRB W100)

  • Results from the ouabain study
  • Experimental design for the variable potassium and sodium studies
  • Hysteresis problem, need for random sampling
  • Suggestions for conducting experiments, collecting data
  • Diffusion potential model and the Goldman-Hodgkin-Katz (GHK) constant field equation

Preparation for next time

  • Use the GHK equation to predict membrane potentials in variable potassium and sodium solutions
  • Be prepared for a possible quiz on the reading and/or subject matter covered today

Laboratory  (Wednesday 7 Sep – 1 pm GRB W112)

  • Prepare crayfish muscle and measure Em in response to varying extracellular concentrations of potassium and sodium ion, using the solutions available in the laboratory

Preparation for next time

  • Preliminary analysis of the results from the variable potassium series; be prepared to discuss the findings
  • Read chapter 2 of the manual through page 19 (skim over the dissection section)
  • Be prepared to discuss why we immediately read a constant Em as soon as the electrode tip penetrates a cell, and why moving the tip to different location within the cell does not affect the measurement
  • Be prepared to discuss what would happen if membrane permeability to sodium ions suddenly increased by a factor of 1000
  • Be prepared for a possible quiz on the reading and/or subject matter covered today

Created by David R. Caprette (caprette@rice.edu), Rice University 14 Oct 97
Updated 14 Aug 11
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