Resting Membrane Potential in Cells

Resting Membrane Potential Measurement

• The cell membrane of living cells has a membrane potential (polarized electrically).
• This electrical potential is due to the attraction between charges.
• The force of attraction between charges has the potential to create force and perform work.
• A change in this force indicates a signal.
• Nerve cells produce signals, which are changes in electrical potential.

Genesis of Resting Membrane Potential

• The resting membrane potential is generated by several factors.
• Ion Channels: Channels allow specific ions to leak across the cell membrane.
• Sodium-Potassium Pump: This pump actively transports sodium out of the cell and potassium into the cell.
• Negatively Charged Molecules: Proteins and other organic molecules inside the cell are negatively charged.
• These negatively charged molecules are unable to cross the cell membrane, making the inside of the cell negative.
• Selective Permeability: The resting cell membrane is more permeable to potassium ions (K+) than to sodium ions (Na+).
• K+ Channels: Potassium channels are open (leak channels) at rest, allowing K+ to move more easily.
• Na+ Channels: Sodium channels are closed at rest, making it difficult for Na+ to move across the membrane.
• Calcium Ions (Ca2+): Calcium ions guard the Na+ channels from the outside and prevent Na+ from entering the cell at rest.
• Sodium Potassium Pump: This pump actively transports 3 Na+ ions out of the cell for every 2 K+ ions transported into the cell, contributing to the negative charge within the cell.

Distribution of Main Charged Substances in Body Fluids

• Extracellular Fluid (ECF) contains high concentrations of sodium (Na+) and chloride (Cl-) ions.
• Intracellular Fluid (Cell) contains high concentrations of potassium (K+) ions and fixed negatively charged proteins and organic molecules.
• Fixed anions are trapped inside the cell and contribute to the negative charge.

Properties of Charged Chemicals

• Electrical force: The attraction or repulsion between charged particles can generate a force that can perform work.
• Resting membrane potential: This is the potential difference between the inside and outside of a cell membrane at rest.

Exitable Cells

• Nerve cells: Resting membrane potential is typically -70 mV.
• Muscle cells: Resting membrane potential is typically -90 mV.

Importance of Resting Membrane Potential

• It's essential for cells to perform their functions, especially excitable cells like nerve and muscle cells.
• A change in membrane potential can signal a stimulus.

Genesis of Resting Membrane Potential

• Ion Channels: These allow for the leakage of ions across the cell membrane.
• Sodium-Potassium (Na/K) Pump: This protein pumps 3 Na+ ions out of the cell for every 2 K+ ions pumped in. It's electrogenic, creating a potential difference (negative inside, positive outside).
• Fixed Anions: Proteins and organic molecules inside the cell carry a negative charge and cannot cross the cell membrane, further contributing to the negative charge inside the cell.