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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.
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