Mechanisms of Ion Movement Across Cell Membranes

Overview

• Cells in the nervous system send signals to the brain by moving ions across their plasma membranes.
• Two main mechanisms for ion movement: passive transport and active transport.
• Focus on sodium (Na+) and potassium (K+) ions.
• Relevant to various cell types, particularly neurons.

Passive Transport

• Characteristics:
  • Does not require energy.
  • Utilizes proteins in the cell membrane that act as channels.
  • Facilitates diffusion of ions from high to low concentration.
• Examples:
  • Sodium Channels:
    • Sodium ions move from high concentration outside the cell to lower concentration inside the cell.
  • Potassium Channels:
    • Potassium ions move from inside the cell to higher concentration areas outside the cell.

Active Transport

• Characteristics:
  • Requires energy in the form of ATP.
  • Proteins involved are often referred to as pumps.
  • Moves ions against the concentration gradient (low to high concentration).
• Example:
  • Sodium-Potassium Pump:
    • Moves sodium ions out of the cell and potassium ions into the cell.

Coordination of Ion Movement

• Channels and pumps work together to manage ion movement.
• Channels allow rapid ion movement across the membrane.
• Pumps restore ions to their original positions after movement.

Application to Neurons

• Mechanisms explain how neurons generate and send signals to the brain by controlling ion movement.