Chapter 1.2 Book Quiz

When the neuron's membrane is at rest, sodium ions are more concentrated ____ the cell, and potassium ions are more concentrated ____. a. inside.... outside. b. inside..... inside. c. outside..... inside. d. outside...... outside.

outside.... inside.

To which part of parts of a neuron does the all-or-none law apply? a. Axons. b. Dendrites. c. Both axons and dendrites.

a. Axons.

Suppose a neuron has a resting potential of -70 mV. If the potential goes to -80 mV, the change would be a ______. a. Depolarization. b. Hyperpolarization.

b. Hyperpolarization.

What does the myelin sheath of an axon accomplish? a. It enables an axon to communicate with other axons. b. It enables action potentials to travel both directions along an axon. c. It enables nutrients to enter the axon. d. It enables action potentials to travel more rapidly.

b. It enables action potentials to travel both directions along an axon.

During the rising portion of the action potential, which ions are moving across the membrane and in which direction? a. Sodium ions move out. b. Sodium ions move in. c. Both sodium and potassium ions move in. d. Potassium ions move in.

b. Sodium ions move in.

Under what conditions does an axon produce an action potential? a. Whenever the membrane is hyperpolarized. b. Whenever the membrane's potential reaches the threshold. c. Whenever the membrane is depolarized. d. Whenever the membrane's potential reaches zero.

b. Whenever the membrane's potential reaches the threshold.

Is it true that we use only 10 percent of our brain? If so, what does that mean? a. At any moment, only 10 percent of brain cells are active. b. You could lose 90 percent of your brain and still do what you are doing now. c. About 90 percent of the brain's neurons are immature and not yet functional. d. No, the statement is false and nonsensical.

b. You could lose 90 percent of your brain and still do what you are doing now.

When the membrane is at rest, the concentration gradient tends to draw sodium ions _____ the cell, and the electrical gradient draws them ______ the cell. a. into.... out of. b. into...... into. c. out of.... into. d. out of..... out of.

b. into...... into.

Which of the following is one way of stating the all-or-none-law? a. The amplitude of the action potential in one axon is the same as that in another axon. b. At a given time, either all axons produce action potentials, or none do. c. All stimuli that exceed the threshold produce equivalent responses in the axon. d. During an action potential, all sodium channels open at the same time.

c. All stimuli that exceed the threshold produce equivalent responses in the axon.

After the action potential reaches its peak, the potential across the membrane falls toward its resting level. What accounts for this recovery? a. The sodium-potassium pump removes the extra sodium. b. Potassium ions move out because their channels are open and the electrical gradient pushes them out. c. Potassium ions move out because their channels are open and the concentration gradient pushes them out. d. Potassium ions move in.

c. Potassium ions move out because their channels are open and the concentration gradient pushes them out.

The sodium-potassium pump moves sodium ions ____and moves potassium ions ______. a. into the cell..... out of the cell. b. into the cell...... into the cell. c. out of the cell.... into the cell. d. out of the cell.... out of the cell.

c. out of the cell.... into the cell.

When the membrane is at rest, the concentration gradient tends to draw potassium ions _____ the cell, and the electrical gradient draws them _____ the cell. a. into.... out of. b. into..... into. c. out of... into. d. out of..... out of.

c. out of... into.