Resting membrane potential and ion channels lab

Nov 6, 2024

Lecture Notes: Neuron Electrical Signals

Overview

  • Neurons send electrical signals; they are electrically excitable cells.
  • Types of electrical signals:
    • Graded Potentials
    • Action Potentials
  • Signal production depends on:
    • Resting Membrane Potential
    • Ion Channels

Resting Membrane Potential (RMP)

  • Difference in charge across the neuron's membrane.
  • Inside of the membrane (cytosol) is more negative than the outside (extracellular fluid).
  • Average RMP is approximately -70 mV.
  • Maintained by ion distribution: high potassium inside, high sodium outside.

Important Ions and Their Movement

  • Potassium (K⁺): High inside, moves outside. Contributes to hyperpolarization if it exits.
  • Sodium (Na⁺): High outside, moves inside. Causes depolarization when entering.
  • Calcium (Ca²⁺): High outside, moves inside. Causes depolarization when entering.
  • Chloride (Cl⁻): High outside, moves inside. Causes hyperpolarization when entering.

Ion Channels and Gates

  • Leakage Channels: Randomly open and close. More potassium than sodium leakage channels.
    • Contribute to RMP.
    • Found in the entire neuron.
  • Ligand-Gated Channels: Open in response to chemicals (hormones or neurotransmitters).
    • Ionotropic: One protein for receptor and channel.
    • Metabotropic: Separate proteins for receptor and channel.
    • Found on neuron somas and dendrites.
  • Mechanical Gates: Open in response to physical stimuli (touch, sound, etc.).
    • Located on sensory neurons.
    • Found on neuron somas and dendrites.
  • Voltage Gates: Open in response to changes in charge.
    • Found on the axon.
    • Types include sodium, potassium, and calcium voltage gates.

Important Concepts

  • Depolarization: The inside becomes more positive (movement towards threshold).
    • Caused by influx of Na⁺ or Ca²⁺.
  • Hyperpolarization: The inside becomes more negative.
    • Caused by efflux of K⁺ or influx of Cl⁻.
  • Threshold Potential: Around -55 mV, necessary for action potential to begin.

Summary

  • Neurons communicate through electrical signals facilitated by ion channels.
  • Understanding the movement of ions and their contribution to depolarization and hyperpolarization is crucial for understanding neuron signaling.
  • Different types of channels and gates regulate ion movement depending on their location and the type of stimulus they respond to.