The Neuron’s Resting Membrane Potential :
The Neuron’s Resting Membrane Potential Membrane – difference in electrical charge between inside and outside of cell
Inside of the neuron is negative with respect to the outside
Resting membrane potential is about –70mV
Membrane is polarized (carries a charge)
Ionic Basis of the Resting Potential :
Ionic Basis of the Resting Potential Factors contributing to even distribution of ions (charged particles)
Random motion – particles tend to move down their concentration gradient
Electrostatic pressure – like repels like, opposites attract
Factors contributing to uneven distribution of ions
Selective permeability to certain ions
Sodium-potassium pumps
Ions Contributing to Resting Potential :
Ions Contributing to Resting Potential Sodium (Na+)
Chloride (Cl-)
Potassium (K+)
Negatively charged proteins (A-)
Synthesized within the neuron
Found primarily within the neuron
The Neuron at Rest :
The Neuron at Rest Ions move in and out through ion-specific channels
K+ and Cl- pass readily
Little movement of Na+
A- don’t move at all, trapped inside
The Neuron at Rest (continued) :
The Neuron at Rest (continued) Equilibrium Potential
The potential at which there is no net movement of an ion – the potential it will move to achieve when allowed to move freely
Na+ = 120mV
K+ = 90mV
Cl- = -70mV (same as resting potential)
The Neuron at Rest (continued) :
The Neuron at Rest (continued) Na+ is driven in by both electrostatic forces and its concentration gradient
K+ is driven in by electrostatic forces and out by its concentration gradient
Cl- is at equilibrium
Sodium-potassium pump – active force that exchanges 3 Na+ inside for 2 K+ outside
Slide 8:
The passive and active factors that influence the distribution of Na+, K+, and Cl– ions across the neural membrane The Neuron at Rest (continued)