AL

Electrically active cell membranes

Nervous System Overview

  • Key Functions of the Nervous System

    • Sensation: The detection of stimuli from the environment.

    • Integration: Processing and interpreting sensory input.

    • Response: Acting upon the sensory inputs based on integration.

  • Functions are heavily reliant on neurons and the excitable membrane that generates electrical signals.

  • Communication is primarily facilitated through action potentials and graded potentials.

Electrically Active Cell Membranes

  • Cell Membrane Structure:

    • Composed mainly of a phospholipid bilayer.

    • Functions as a gatekeeper, selectively allowing substances to cross.

    • Charged particles (ions) require assistance to traverse the membrane due to their hydrophilic nature.

  • Role of Ion Channels:

    • Channel proteins facilitate movement of ions across the cell membrane.

    • Types include ligand-gated, mechanically gated, voltage-gated, and leakage channels.

Sodium-Potassium Pump

  • A specialized carrier protein termed ATPase that utilizes energy from ATP to operate.

  • Function: Transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, maintaining concentration gradients.

    • Higher Na+ concentration outside vs. higher K+ concentration inside the cell.

Ion Channel Classification

  • Ion Channel Characteristics:

    • Specified by pore diameter; relates to interaction with water molecules.

    • Can be selective based on charge or size (size exclusion).

  • Gating of Ion Channels:

    • Ligand-Gated Channels: Open in response to neurotransmitter binding, facilitating ion movement.

    • Mechanically Gated Channels: Open due to physical deformation (e.g., touch or pressure).

    • Voltage-Gated Channels: Respond to changes in membrane potential, allowing ions to cross when depolarization occurs.

    • Leakage Channels: Randomly gated, contributing to resting membrane potential.

Terms to Know

  • Phospholipid Bilayer:

    • The structural foundation of cell membranes, featuring a double-layer of phospholipid molecules.

  • Hydrophobic Core:

    • The inner water-repellent region of the phospholipid bilayer.

  • Transmembrane Proteins:

    • Proteins that span across the cell membrane, interacting with both intracellular and extracellular environments.