Final answer:
Hyperkalemia leads to neurons being more excitable, as opposed to harder to excite or hyperpolarize, because it causes partial depolarization and brings the resting potential closer to the threshold for action potentials. The correct option is B) neurons are hyperexcitable because their resting potential is closer to the threshold.
Step-by-step explanation:
The primary problem in hyperkalemia is that neurons are harder to excite because their resting potential is hyperpolarized. All other options are incorrect since hyperkalemia causes a partial depolarization of the plasma membrane leading to a resting potential that is less negative, thus making neurons more excitable and bringing them closer to the threshold.
Normal neuronal function relies on the resting membrane potential, which is determined by the concentration gradients of various ions, particularly sodium (Na+) and potassium (K+). Neurons maintain a negatively charged resting state due to the sodium-potassium pump, which removes three Na+ ions for every two K+ ions it brings into the cell. In hyperkalemia, the elevated extracellular potassium concentration can decrease the gradient across the plasma membrane, causing partial depolarization and making neurons more likely to fire with smaller stimuli.
The correct option is B) neurons are hyperexcitable because their resting potential is closer to the threshold.