Local Currents Drive the Propagation of Action Potentials Along Axons
- The diffusion of sodium ions both inside and outside the axon generates local currents, which spread the action potential down the axon, ensuring that nerve signals are transmitted quickly.
- Think of an action potential as a wave at a sports stadium.
- Each person stands up and sits down, creating a wave that moves around the stadium.
- Similarly, an action potential is a wave of electrical changes that travels along the axon.
Local Currents Are The Key to Propagation
- Depolarization occurs when sodium ions ($Na^+$) flood into the axon, reversing the charge across the membrane.
- This creates a high concentration of $Na^+$ inside the depolarized region compared to its neighboring areas.
- Local currents are formed as $Na^+$ ions diffuse:
- Inside the axon: From the depolarized region to the adjacent polarized region.
- Outside the axon: In the opposite direction, from the polarized region to the depolarized region.
Local currents are short-distance movements of ions that help spread the electrical signal along the axon.
Reaching the Threshold Potential
- The resting potential of a neuron is about −70 mV.
- Local currents reduce the charge difference in the neighboring region, raising the membrane potential to about −50 mV, the threshold potential.
- Once this threshold is reached, voltage-gated sodium channels open, allowing more $Na^+$ ions to enter and triggering depolarization in the next section of the axon.
The Role of Local Currents in Propagation
- Local currents are essential for spreading the action potential along the axon.
- By diffusing sodium ions to neighboring regions, they help reach the threshold potential and trigger the next wave of depolarization.
- How does the concept of local currents relate to other biological systems that rely on gradients, such as osmosis or diffusion?
- What does this tell us about the universality of certain principles in biology?
- What is the role of local currents in the propagation of an action potential?
- Can you explain how local currents help propagate an action potential?
