Understanding Neuron Resting Membrane Potential

Oct 16, 2024

Neuron Resting Membrane Potential

Overview

  • The resting membrane potential (often called resting potential) describes the stable separation of charges across a neuron's cell membrane when the neuron is at rest (not receiving input).
  • Characterized by:
    • More positive charges (cations) on the outside of the membrane.
    • More negative charges (anions) on the inside of the membrane.

Structure

  • Neuron Drawing:
    • Soma (cell body) and axon, typically a thin process, here a thick representation for clarity.
    • Dendrites, normally thin, drawn large.

Key Terms

  • Anions: Negatively charged ions inside the membrane.
  • Cations: Positively charged ions outside the membrane.

Charge Separation

  • More cations outside and more anions inside the neuron membrane.
  • Voltage difference measured as the difference between inside and outside (outside set to zero).
    • Typical resting potential: ~-60 millivolts (mV).

Ion Concentration Gradients

  • Concentration differences (gradients) of ions across the cell membrane are crucial.
  • Key Ions:
    • Cations:
      • Potassium (K+)
      • Sodium (Na+)
      • Calcium (Ca2+)
    • Anions:
      • Chloride (Cl-)
      • Organic anions (e.g., proteins with net negative charge).

Ion Concentration Details

  • Organic Anions and Potassium (K+):
    • Higher concentration inside the neuron.
  • Sodium (Na+), Calcium (Ca2+), and Chloride (Cl-):
    • Higher concentration outside the neuron.

Forces Acting on Ions

  • Electrical Force:

    • Ions attracted to opposite charges across the membrane.
    • Organic Anions: Attracted outside (positive outside).
    • Potassium and Sodium: Attracted inside (negative inside).
    • Chloride: Driven out (like organic anions).
    • Calcium: Attracted inside.
  • Diffusion (Chemical) Force:

    • Ions move from high to low concentration.
    • Organic Anions: Driven out (high inside concentration).
    • Potassium: Conflicted, diffuses out but electrically attracted in.
    • Sodium: Matches electrical force, moves in (high outside concentration).
    • Chloride: Driven in by diffusion but out by electrical.
    • Calcium: Moves in.

Electrochemical Driving Forces

  • Combination of electrical and diffusion forces.
  • Neurons utilize these forces for their function.

Future Discussion

  • Next topic includes how resting membrane potential is created and its relation to ion concentration differences.