Neuron Resting Membrane Potential

Introduction

• The concept of the resting membrane potential of a neuron.
• Typically, neurons at rest have a stable separation of charges across their cell membrane.

Neuron Structure

• Neurons consist of:
  • Soma (cell body)
  • Axon - thin, long process
  • Dendrites
• For the illustration, a distorted, large axon and dendrite were drawn for clarity.

Charge Separation Across Membrane

• Resting potential: More positive charges (cations) outside and more negative charges (anions) inside the membrane.
• Both anions and cations are present on both sides, but there's a net difference.
• Common resting potential: around -60 millivolts (mV).

Key Ions in Resting Potential

• Cations (positively charged ions):
  • Potassium (K⁺)
  • Sodium (Na⁺)
  • Calcium (Ca²⁺)
• Anions (negatively charged ions):
  • Chloride (Cl⁻)
  • Organic anions (OA⁻), largely proteins with a net negative charge

Concentration Gradients

• Concentration differences, or gradients, are critical for neuron function:
  • Inside neuron: High concentration of organic anions and potassium
  • Outside neuron: High concentration of sodium, calcium, and chloride

Forces Acting on Ions

• Electrical Force:
  • Attracted to opposite charges across the membrane.
  • E.g., negatively charged anions are attracted to positive charges outside the neuron.
• Diffusion Force (Chemical Force):
  • Movement from areas of high to low concentration.
  • E.g., potassium has a higher concentration inside, prompting diffusion outside.

Electrochemical Driving Forces

• Combination of electrical and diffusion forces.
• Organic anions: Both forces drive them out of the neuron.
• Potassium: Electrical force tries to pull it inside, diffusion force pushes it outside.
• Sodium & Calcium: Both forces drive them into the neuron.
• Chloride: Electrical force pushes it out, diffusion force pulls it in.

Conclusion

• Neurons use these electrochemical forces for their functions.
• The next topic will explore how the resting membrane potential is established and its relation to ion concentration differences.