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
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