Lecture Notes: Resting Membrane Potential and Ion Gradients

Introduction

• Membrane Permeability: Altering it leads to electrical and chemical disequilibrium.
• Electrical Disequilibrium: Difference in ion concentration creates potential energy.
• Key Ions: Sodium (Na⁺) and Potassium (K⁺).

Properties Influencing Resting Membrane Potential

1. Ion Concentration Difference
   • Focus on Na⁺ and K⁺.
   • K⁺ plays a more significant role.
2. Membrane Permeability
   • More permeable to K⁺ than Na⁺ due to more K⁺ leaky channels.

Factors Influencing Diffusion Rates

• Size of Ions: Smaller ions diffuse faster.
• Membrane Composition
  • Influences the number of protein channels (leaky channels).
  • Importance of leaky Na⁺ and K⁺ channels.
• Steepness of Concentration Gradient
  • Steep Na⁺ and K⁺ gradients drive ion movement.

Electrical and Chemical Gradients

• Electrical Gradient: Due to charge differences inside and outside the cell.
• Dynamic Steady State: Energy investment is required to maintain disequilibrium.

Ion Movement and Equilibrium

• K⁺ Efflux: K⁺ moves out, creating a chemical and electrical gradient.
• Development of Electrochemical Equilibrium: Balance between chemical and electrical gradients.
• Nernst Equation: Describes the relationship between ion concentration and membrane potential.

Role of Protein Channels and Pumps

• Leaky Channels: Allow passive ion movement to establish resting potential.
• Sodium-Potassium Pump (Na⁺/K⁺ ATPase):
  • Uses ATP to move ions against gradients.
  • Pumps 3 Na⁺ out and 2 K⁺ in, reinforcing the negative charge inside.

Resting Membrane Potential (RMP)

• Typical RMP: Approximately -70 millivolts, varies slightly between neurons.
• Influence of Ion Movement: Continuous movement of ions maintains RMP.

Future Topics

• Alteration of Membrane Permeability: Using chemically and voltage-gated channels to create electrical signals for neuron communication.