Action Potential in Neurons

The action potential is a fundamental process in nerve impulse transmission along neurons. It involves the movement of sodium and potassium ions across the neuron's membrane at specific points.

Definition: An action potential describes the movement of sodium and potassium ions at a single point on the neuron's membrane.

The process of an action potential can be broken down into several stages:

1. Resting Potential: In a resting neuron, there is a polarized state due to the active transport of sodium and potassium ions. This creates a charge difference known as the resting potential.

   Highlight: The resting potential is characterized by more positive charge on the outside of the membrane compared to the inside, with a higher concentration of sodium ions on the exterior.

2. Depolarization: The depolarization process in nerve impulses begins when:

   • Sodium channels open in response to a stimulus.

   • Sodium ions diffuse into the neuron.

   • If enough sodium enters to reach the threshold, additional voltage-sensitive sodium gates open, allowing more sodium to enter.

   Vocabulary: Depolarization refers to the reduction of the membrane potential, making the inside of the neuron less negative.

3. Repolarization: The repolarization of axon during nerve signal transmission occurs when:

   • Sodium channels close.

   • Voltage-sensitive potassium gated channels open.

   • Potassium ions diffuse out of the neuron.

   • This process restores the negative charge inside the axon.

   Example: During repolarization, the outflow of potassium ions is like opening a dam, allowing positive charges to flow out and restore the original electrical state of the neuron.

Understanding this process is crucial for comprehending how nerve impulses travel along neurons as a series of action potentials, enabling the transmission of signals throughout the nervous system.