Welcome to Bioc 415

• Syllabus
• Assignments

Scheduled labs

• First session
• Membrane labs
• Nerve labs
• Nerve/muscle labs

On-line resources

Introductory lab manual (Bioc 211)
Bioc 311 resources

Bioc 415 manual (pdf)

Bioc 415 appendixes (pdf)

Membrane Depolarization

Start with a cell membrane in the normal state, with membrane potential of -65 mV. The yellow band represents a semi-permeable membrane. Red indicates surplus of positive charge, blue indicates surplus of negative charge (deficit of positive ions). Every positive ion has a negative counter-ion, but some of the ion pairs are separated as shown.

Change the extracellular medium to a solution with five times the normal concentration of potassium chloride. Potassium ions carry positive charge to the interior, neutralizing some of the excess negative charge.

Now in the new steady state, there is less displaced charge across the membrane.

Throughout this event, an equal amount of positive and negative charge was present in the system. The membrane simply separates an amount of charge that is determined by existing conditions.

[hyperpolarization]