Neurons and Action Potentials

Neuron Communication

• Neurons communicate through electrical impulses, similar to a basic app sending a constant signal.
• An impulse travels from one neuron to another through axons.
• This impulse is called an action potential, a fundamental aspect of anatomy and physiology.

Electricity Basics

• The body is electrically neutral but has areas of varying charges.
• Voltage: Potential energy from separated charges, measured in millivolts in the body.
• Current: Flow of electrical charge across membranes.
• Resistance: Elements that hinder the flow, insulators (high resistance), conductors (low resistance).

Resting Membrane Potential

• A neuron at rest is more negative inside than outside (-70 millivolts).
• Sodium ions (Na+) are outside; Potassium ions (K+) and negatively charged proteins are inside.
• This state is known as being polarized.

Sodium-Potassium Pump

• Pumps 3 Na+ out and 2 K+ into the cell, maintaining a negative inside charge and positive outside.

Ion Channels

• Voltage-gated channels: Open/close with changes in membrane potential.
• Ligand-gated channels: Open with a neurotransmitter.
• Mechanically-gated channels: Open from physical stretching.

Action Potential

• Initiated when a stimulus causes enough depolarization reaching a threshold (-55 millivolts).
• Depolarization: Na+ ions rush in, potential becomes positive (+40 millivolts).
• Repolarization: K+ channels open letting K+ out, restoring negative charge.
• Hyperpolarization: Temporary over-correction before returning to resting state.
• Refractory Period: Neuron can't respond to new stimulus during repolarization.

Frequency and Speed of Action Potentials

• Frequency indicates stimulus strength (e.g., delicate vs. strong tasks).
• Speed affected by myelin sheath and node of Ranvier.
  • Saltatory Conduction: Impulses leap between nodes, speeding up transmission.

Conclusion

• Neurons use electrical potentials to communicate signals.
• Action potentials involve phases: resting, depolarization, repolarization, hyperpolarization.
• Next steps involve how these signals move to other neurons.

Additional Information

• Crash Course Kids on YouTube for educational content for younger audiences.