Final answer:
The correct chronological order for the events regarding K+ in an action potential is: reaching the threshold, opening of K+ voltage-gated channels, start of repolarization, beginning of K+ inactivation, followed by hyperpolarization. This sequence ensures that the neuron can fire an action potential and then reset to its resting state.
Step-by-step explanation:
Order of Events in the Generation of an Action Potential
Understanding how an action potential is generated and propagated along neurons is essential in biology. The sequence of events involves K+ ions and various stages of the neuron's electrical state. To arrange the events concerning K+ and the generation of the action potential in chronological order:
- Threshold is reached.
- K⁺ voltage-gated channels open.
- Repolarization starts.
- K⁺ inactivation begins.
- Hyperpolarization.
Firstly, a depolarizing stimulus causes the membrane potential to reach the threshold, which triggers the action potential. Subsequently, voltage-gated K+ channels open as the membrane potential rises, allowing K+ to flow out of the neuron, which starts repolarization. K+ outflow continues even as the voltage-gated Na+ channels begin to inactivate, leading to K+ inactivation. Finally, this continued outflow of K+ causes the membrane to overshoot the resting potential, resulting in hyperpolarization, before the cell returns to its resting state.