Final answer:
The correct phases of an action potential are depolarization, repolarization, and hyperpolarization. These phases are crucial for the propagation of nerve impulses, with depolarization involving sodium ion influx, repolarization involving potassium ion efflux, and hyperpolarization defining the refractory period.
Step-by-step explanation:
The phases of an action potential involve a sequence of changes in the membrane potential of a neuron. They are integral for the conduction of electrical signals down the neuron's axon. The correct phases to be identified in the question are:
- Depolarization: This is the initial phase where the neuron's membrane potential becomes less negative (or more positive), reaching the threshold potential. This occurs due to the influx of Na+ ions into the neuron.
- Repolarization: Following depolarization, the neuron's membrane potential returns to a negative value as K+ ions exit the cell.
- Hyperpolarization: During this phase, the membrane potential becomes even more negative than the resting potential, as K+ ions continue to leave the cell. This ensures that the neuron does not fire again immediately and sets a refractory period.
These phases are essential for the propagation of nerve impulses across the neuron. The two incorrect options in the question are 'hyperpotential' and 'afterpotential', which are not recognized terms in the context of an action potential. Therefore, the correct options in the final answer are depolarization, repolarization, and hyperpolarization.