Chap 6 Resting Membrane Potential RMP

Chapter 6 Resting Membrane Potential (RMP)

What is the Resting Membrane Potential (RMP)?

ELECTRIC POTENTIAL – separation of opposite charges between 2 points. (“Has the potential to do electrical work if allowed to come together!”)

vs.

large potential difference small potential difference

Magnitude of charge separation = potential difference

** measured in volts (1 Volt = 1000 mV)

MEMBRANE POTENTIAL = charge separation across cell membrane (separation of overall net charge on either side of a membrane)

** The greater the difference in charge separation across the membrane  the greater the membrane potential (greater voltage).

Potential difference (voltage across membrane)

Membrane potential (Sherwood, 1995)

Actual Cell Unequal distribution of ions across membrane (particularly Na+, K+ and A- (Anions).

[A-] trapped anions (neg. charged) inside cell ** Neg. charged proteins, DNA, RNA and ATP

ICF = intracellular fluid ECF = extracellular fluid ICF ECF

RESTING MEMBRANE POTENTIAL (RMP) Fig. 6.27 (Fox)

** voltmeter (needle electrodes)

RMP = - 70 mV

All cells in a “resting state” (no stimulation) have a separation of charges across the cell membrane (or RMP). The ICF (inside) is slightly more negative than the ECF.

Cell is like a small battery ready to discharge!

** By convention, the sign of the voltage designates the overall net charges inside the membrane as compared to the outside!

Ex.

An electric impulse is just a series of changes in membrane potential!

Change in MEMBRANE POTENTIAL (2 TYPES)
1. Graded Potentials
2. ** Action Potentials (AP)

A