Nervous system 4

• What is the resting membrane potential (RMP)?

  The resting membrane potential (RMP) is the stable, negative charge inside a neuron compared to the outside when the neuron is at rest, not sending signals. It typically ranges from -70 mV to -90 mV.
• Why is the inside of a neuron negatively charged compared to the outside?

  The inside of the neuron is negatively charged because of the unequal distribution of ions across the cell membrane, mainly due to the action of the sodium-potassium pump and the movement of potassium ions (K+) out of the cell.
• What causes the difference in the composition of the extracellular fluid (ECF) and intracellular fluid (ICF)?

  the difference in the composition is largely caused by the sodium-potassium pump (Na+/K+ ATPase), which actively transports 3 sodium ions (Na+) out of the cell and 2 potassium ions (K+) in, creating a concentration gradient.
• What happens when potassium ions (K+) move across the membrane?

  when K+ ions move out of the cell (efflux), it makes the inside of the cell more negative. As more K+ ions leave, an electrical gradient starts to build up that opposes the further movement of K+. Eventually, the electrical gradient becomes strong enough to counteract the concentration gradient, and at equilibrium, the K+ ions move in and out at the same rate.
• What is the electrochemical equilibrium potential for K+?

  the electrochemical equilibrium potential is the voltage at which the electrical and concentration gradients for an ion are equal and opposite. For K+, this equilibrium potential is approximately -97 mV.
• How can the equilibrium potential for K+ be calculated?

  the equilibrium potential for an ion (E) can be calculated using the Nernst Equation:

  E = 58 \times \log \left( \frac{[C]{\text{outside}}}{[C]{\text{inside}}} \right)
• Why does the RMP not exactly match the equilibrium potential for K+?

  the RMP is primarily determined by K+ efflux (movement of K+ out of the cell), but Na+ influx (movement of sodium ions into the cell) also contributes slightly. Since the membrane is more permeable to K+ than to Na+, the RMP is close to, but slightly less negative than the K+ equilibrium potential.
• How does the permeability of Na+ affect the resting membrane potential?

  the permeability of Na+ is much lower than K+, but since Na+ ions are highly concentrated outside the cell, some Na+ ions do enter the cell, making the inside less negative. This causes the RMP to move slightly less negative than the K+ equilibrium potential (around -70 mV instead of -97 mV).
• What is the Goldman Constant Field Equation used for?

  the Goldman Constant Field Equation is an extension of the Nernst equation that takes into account the concentration and permeability of all ions involved in generating the membrane potential, not just one ion like K+. It provides a more accurate calculation of the resting membrane potential by considering the contribution of multiple ions like K+, Na+, and Cl-.
• What is the primary factor contributing to the resting membrane potential (RMP)?

  the primary factor contributing to the RMP is the efflux of K+ ions out of the neuron, which creates a negative charge inside the cell. A smaller contribution comes from the influx of Na+ ions, but their effect is much less significant due to their lower permeability.
• Why do neurons have a negative resting membrane potential?

  neurons have a negative resting membrane potential due to the combined effects of the sodium-potassium pump (which moves more Na+ out than K+ in) and the permeability of the membrane to K+, which leads to a net efflux of K+ and a buildup of negative charge inside the cell.
• What is the importance of the resting membrane potential (RMP)?

  the RMP is crucial because it sets up the conditions for action potentials, which are essential for neurons to send electrical signals. A stable RMP allows the neuron to respond quickly to stimuli and transmit messages in the nervous system.