Q: Which equation best represents the action of the sodium-potassium pump?

$$3\ \text{Na}^+_{\text{in}} \rightarrow 3\ \text{Na}^+_{\text{out}}$$ and $$2\ \text{K}^+_{\text{out}} \rightarrow 2\ \text{K}^+_{\text{in}}$$

Question 1

Which of the following best describes the electrochemical gradient for potassium ions in a typical neuron at rest?

Accepted Answer

The electrical gradient drives K+ into the cell, while the concentration gradient drives K+ out of the cell.

Question 2

Given the standard concentrations of sodium and potassium, which statement is correct regarding their distribution in a neuron at rest?

Accepted Answer

Sodium concentration is higher outside the cell than inside, while potassium concentration is higher inside the cell than outside.

Question 3

What is the effect of blocking the sodium-potassium pump (Na+/K+ ATPase) in a neuron?

Accepted Answer

The concentration of potassium inside the cell will decrease.

Question 4

Which equation best represents the action of the sodium-potassium pump?

Accepted Answer

$$3\ 	ext{Na}^+_{	ext{in}} ightarrow 3\ 	ext{Na}^+_{	ext{out}}$$ and $$2\ 	ext{K}^+_{	ext{out}} ightarrow 2\ 	ext{K}^+_{	ext{in}}$$

Question 5

A neuron’s membrane potential changes from $$-90\ 	ext{mV} to$$ $$-10\ 	ext{mV}. $$What term best describes this change?

Accepted Answer

Depolarization

Question 6

Which of the following is the most important factor in generating the resting membrane potential?

Accepted Answer

K+ concentration gradient

Question 7

Which statement about graded and action potentials is correct?

Accepted Answer

Action potentials are all identical, whereas graded potentials can vary in size.

Question 8

Which of the following statements about graded potentials is FALSE?

Accepted Answer

Graded potentials occur mainly in axons.

Question 9

When voltage-gated sodium channels open in response to a stimulus, what effect does it have on the neuron?

Accepted Answer

Both b and c.

Question 10

A graded potential is strongest at the:

Accepted Answer

Site of stimulation.

Question 11

An excitatory postsynaptic potential (EPSP) is:

Accepted Answer

a graded depolarization produced by the arrival of a neurotransmitter.

Question 12

When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what results?

Accepted Answer

Temporal summation.

Question 13

The EPSPs from two different synapses occur at the same time and cause a larger depolarization than either one alone can cause. This is an example of:

Accepted Answer

Spatial summation.

Question 14

Casey is taking a new medication that blocks potassium channels. What stage of an action potential would be MOST affected by this drug?

Accepted Answer

The repolarization phase.

Question 15

When an action potential is at its peak, the electrical gradient forces potassium:

Accepted Answer

Out of the cell.

Question 16

What happens when the neuron reaches threshold ($$-55\ 	ext{mV}$$)?

Accepted Answer

Voltage-gated sodium channels open and sodium rushes into the cell.

Question 17

During the relative refractory period, a larger-than-normal depolarizing stimulus can:

Accepted Answer

bring the membrane to threshold and initiate a second action potential.

Question 18

During saltatory conduction, action potentials are generated:

Accepted Answer

Only at the nodes of Ranvier of myelinated axons.

Question 19

In unmyelinated axons, action potentials are propagated by ________ conduction.

Accepted Answer

Continuous.

Question 20

Dr. Roberts is testing a new drug that blocks sodium channels in the axons of a neuron. Which of the following statements is correct?

Accepted Answer

The drug would prevent the propagation of action potentials.

Nervous Tissue and Nervous System: Ionic Mechanisms, Membrane Potentials, and Signal Propagation

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