Describe the electrical and chemical events that underlie an action potential.
What will be an ideal response?
Action potentials are generated when the summed signal entering a neuron is excitatory enough to hypopolarize/depolarize the cell membrane approximately 10 mV compared to the resting membrane potential. That excitatory signal comes from neurotransmitters that bind to specific receptors on a neuron. Following that initial graded potential, voltage-gated sodium channels open, and sodium ions enter the neuron. Since sodium ions carry a positive charge, this prompts the next segment of the axon to become depolarized, and the action potential is propagated down the axon in this manner. The depolarization also opens voltage-gated potassium channels, allowing potassium ions to leave the neuron. Since potassium ions carry a positive charge, this results in hyperpolarization of the cell membrane as the neuron's electrical charge becomes slightly more negative than at rest. Movement of sodium ions into the neuron and potassium ions out of the neuron results in the rapid depolarization and then hyperpolarization of the cell's membrane during the action potential.
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