Time (milliseconds) Analysis 1. Determine about how long an action potential lasts. . 2. State whether voltage-gated sodium channels are open or closed at point A. 3. State whether voltage-gated potassium channels are open or closed at point B. 4. Critical Thinking Recognizing Relationships What causes the membrane potential to become less negative at point A? 5. Critical Thinking Recognizing Relationships What causes the membrane potential to become more negative at point B