Question 1

Which of the following best describes the electrochemical gradient for potassium (K+) 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

Suppose the extracellular fluid has a chloride (Cl-) concentration of 120 mM, while the cytosol has 60 mM Cl-. The cytosol is more negative than the extracellular fluid. Which statement is correct regarding the movement of Cl- ions?

Accepted Answer

The concentration gradient favors a net movement out of the cell, the electrical gradient favors movement into the cell.

Question 3

In a neuron at rest, which ion has a higher concentration outside the cell, and which has a higher concentration inside the cell?

Accepted Answer

Sodium; potassium.

Question 4

Which of the following statements is true regarding how the concentration gradient affects sodium ions when a cell is at rest?

Accepted Answer

The concentration gradient drives sodium ions into the cell.

Question 5

The sodium-potassium pump (Na+/K+ ATPase) moves ions against their electrochemical gradients. Which of the following best describes its action?

Accepted Answer

It ejects 3 sodium ions from the cell and transports 2 potassium ions into the cell.

Question 6

If the sodium-potassium pump is blocked by a toxin, what will happen to the concentration of potassium inside the cell over time?

Accepted Answer

The concentration of potassium will decrease.

Question 7

Which of the following is the MOST important factor in generating the resting membrane potential of a neuron?

Accepted Answer

K+ concentration gradient.

Question 8

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

Accepted Answer

Depolarization.

Question 9

Which of the following statements about graded potentials is FALSE?

Accepted Answer

Graded potentials occur mainly in axons.

Question 10

Action potentials are an all-or-none phenomenon, meaning that once the membrane potential reaches approximately what value, they will always occur?

Accepted Answer

$$-55\ \mathrm{mV}$$

Question 11

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 12

A graded potential is strongest at which location?

Accepted Answer

Site of stimulation.

Question 13

An excitatory postsynaptic potential (EPSP) is:

Accepted Answer

A graded depolarization produced by the arrival of a neurotransmitter.

Question 14

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

Accepted Answer

Temporal summation.

Question 15

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 16

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 17

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

Accepted Answer

Out of the cell.

Question 18

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 19

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

Accepted Answer

Continuous.

Question 20

During saltatory conduction, action potentials are generated:

Accepted Answer

Only at the nodes of Ranvier of myelinated axons.

Nervous Tissue: Ionic Basis, Membrane Potentials, and Signal Propagation

Study Guide - Practice Questions

Study Guide - Flashcards