A&P Neurophysiology Practice Test 2026 – Complete Exam Preparation

The electrochemical gradient for potassium ions at resting potential arises from the interplay of both a concentration gradient and an electrical gradient. At resting potential, there is a higher concentration of potassium ions inside the cell compared to the outside. This establishes a chemical gradient that drives potassium ions out of the cell. However, as potassium ions begin to diffuse out, the interior of the cell becomes more negatively charged relative to the outside, creating an electrical gradient that pulls potassium ions back into the cell.

Option B accurately describes this scenario by recognizing that the chemical gradient pushes potassium ions out of the cell while the electrical gradient pulls them back in. The combination of these two forces—the outward chemical force due to the concentration difference and the inward electrical force due to the negative charge inside the cell—defines the electrochemical gradient for potassium ions.

In contrast, other options either misrepresent the nature of the gradients or fail to acknowledge the role of both components in creating the electrochemical gradient. Understanding this interplay is crucial for grasping how neuronal excitability and action potentials function in neurophysiology.