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.