Understanding Neurons and Action Potentials

Aug 6, 2024

Neurons and Electrical Impulses: Action Potentials

Communication in Neurons

  • Neurons communicate thoughts, actions, and emotions using electrical impulses.
  • These impulses are identical in strength and speed; they differ in frequency.

The Action Potential

  • Action Potential: The fundamental process of neuronal communication.
  • Neurons fire electrical impulses when stimulated enough.
  • Impulses read by the brain like binary code.

The Role of Electricity

  • The body is electrically neutral but contains areas of differing charges.
  • Barriers/membranes keep charges separated to build potential energy.
  • Voltage: Measure of potential energy from separated charges (measured in millivolts in the body).
  • Current: Flow of electricity from one point to another, influenced by voltage and resistance.
  • Resistance: The obstruction to current flow (insulators vs. conductors).

Resting Membrane Potential

  • A resting neuron is negative inside relative to the outside, known as the resting membrane potential, typically around -70 millivolts.
  • Polarization: The negative state of a resting neuron.
  • Sodium-Potassium Pump: Maintains the resting potential by pumping 3 sodium ions out and 2 potassium ions in.

Ion Channels and Gates

  • Voltage-Gated Channels: Open at specific membrane potentials.
  • Ligand-Gated Channels: Open when specific neurotransmitters bind.
  • Mechanically Gated Channels: Open in response to physical stretching.

Generating an Action Potential

  • Depolarization: A stimulus causes sodium channels to open, raising the internal charge.
  • Must reach a threshold of about -55 millivolts to trigger an action potential.
  • All-or-Nothing: If the threshold isn't reached, the neuron returns to resting state.
  • Upon hitting the threshold, sodium ions flood in, raising the potential to +40 millivolts.

Propagation of Action Potential

  • Repolarization: Potassium channels open, letting potassium out to rebalance the charge.
  • Hyperpolarization: Temporarily drops voltage below resting potential.
  • Refractory Period: Prevents the neuron from responding to new stimuli until back to resting state.

Factors Influencing Action Potentials

  • Frequency: Determines the intensity of the stimulus (e.g., low frequency for delicate tasks, high frequency for strong actions).
  • Speed: Influenced by the presence of a myelin sheath.
  • Saltatory Conduction: Current leaps between Nodes of Ranvier when myelin is present.

Conclusion

  • Neurons use electrical impulses to communicate through action potentials.
  • This process involves intricate electrochemical gradients and ion channels.
  • Next steps involve understanding how action potentials transfer between neurons.