Electrical Potentials

Depolarization occurs because

• more Na⁺ diffuse into the cell than K⁺ diffuse out of it.

• both Na⁺ and K⁺ diffuse into the cell.

• more K⁺ diffuse out of the cell than Na⁺ diffuse into it.

• more K⁺ diffuse into the cell than Na⁺ diffuse out of it.

Repolarization occurs because

• more Na⁺ diffuse into the cell than K⁺diffuse out of it.

• both Na⁺ and K⁺ diffuse into the cell.

• more K⁺ diffuse out of the cell than Na⁺ diffuse into it.

• more K⁺ diffuse into the cell than Na⁺diffuse out of it.

What is the resting membrane potential of a neuron?

• -90 mV

• -70 mV

• -50 mV

• -45mV

Why does hyperpolarization occur?

• potassium efflux causes membrane to become very positive

• the increased potassium ion permeability lasts longer than sodium influx

• more sodium ions diffuse into the cell

• inactivation gates of the sodium ion channels open

During depolarization, which of the following statements about voltage-gated ion channels is TRUE?

• Na⁺ gates open before K⁺ gates

• K⁺ gates open while Na⁺ gates remain closed

• K⁺ gates open before Na⁺ gates

• Na⁺ and K⁺ gates open at the same time

After the passage of the action potential, the sodium-potassium pump reestablishes the resting membrane potential.

• True

• False

An action potential

• prevents the neuron cell membrane from altering its charge.

• causes the outside of the neuron cell membrane to become positive and the inside negative

• causes the inside of the neuron cell membrane to become positive and the outside negative

• causes the inside of the neuron cell membrane to become positive and the outside positive

Action potential propagation occurs in both directions along the axon.

• True

• False

Threshold is the minimum current required for the cell membrane to generate an action potential.

• True

• False

The voltage-gated potassium channels close before the membrane potential is brought back to its resting level.

• True

• False