Resting potential and action potentials Knowledge-Based Practice

Questions

1. 1.

   Which physiological mechanism directly accounts for the afterhyperpolarization (undershoot) phase observed near the end of a neuronal action potential?

   • A) The delayed closure of voltage-gated potassium channels permits a continued efflux of potassium ions toward their equilibrium potential.
   • B) The sudden opening of ligand-gated chloride channels drives a massive influx of negative anions into the cytoplasm.
   • C) The sodium-potassium pump temporarily reverses its pumping direction to export excess intracellular sodium.
   • D) Voltage-gated sodium channels transition from the inactive to the closed state by allowing a transient outward sodium current.
2. 2.

   During an action potential in a neuron, which physiological event is directly responsible for the absolute refractory period?

   • A) Rapid influx of chloride ions through ligand-gated channels
   • B) Complete closure of non-gated potassium leak channels
   • C) Inactivation of voltage-gated sodium channels by their inactivation gates
   • D) Acceleration of the sodium-potassium pump to its maximum transport rate
3. 3.

   Once an axon hillock reaches the threshold potential, which event directly accounts for the rapid depolarization phase of the action potential?

   • A) Rapid opening of voltage-gated sodium channels and the influx of sodium ions into the cell
   • B) Delayed opening of voltage-gated potassium channels and the efflux of potassium ions from the cell
   • C) Sudden inactivation of the sodium-potassium pump preventing active transport across the membrane
   • D) Complete closure of non-gated potassium leak channels across the entire axonal membrane
4. 4.

   Which transport protein directly uses ATP to maintain the concentration gradients of sodium and potassium ions across the neuronal membrane at resting potential?

   • A) Voltage-gated potassium channel
   • B) Sodium-potassium pump
   • C) Potassium leak channel
   • D) Voltage-gated sodium channel
5. 5.

   During the repolarization phase of an action potential in a neuron, which ion movement is directly responsible for restoring the negative intracellular membrane potential?

   • A) Voltage-gated potassium channels open, allowing potassium ions to diffuse out of the axon.
   • B) Voltage-gated sodium channels open, allowing sodium ions to diffuse into the axon.
   • C) Sodium-potassium pumps reverse direction, actively transporting sodium ions into the axon.
   • D) Voltage-gated calcium channels open, allowing calcium ions to diffuse out of the axon.

Answers and step-by-step solutions appear after you finish the test.