Unit 1 Study Q's

To which part or 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

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

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. c) out of...into b) into...into. d) out of...out of

B. When the membrane is at rest, the concentration gradient tends to draw sodium ions INTO the cell, and the electrical gradient draws them INTO the cell (as well).

Under what condition 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

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 in 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 moves 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. c) out of the cell...into the cell b) into the cell...into the cell. d) out of the cell...out of the cell

C. The sodium-potassium pump moves sodium ions OUT OF THE CELL and potassium ions 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. c) out of...into b) into...into. d) out of...out of

C. When the membrane is at rest, the concentration gradient tends to draw potassium ions OUT OF the cell, and the electrical gradient draws them INTO the cell.

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

C. When the neuron's membrane is at rest, sodium ions are more concentrated OUTSIDE the cell, and potassium ions are more concentrated INSIDE.

What does the myelin sheath 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

D. The myelin sheath enables action potentials to travel more rapidly

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

D. The statement is false and nonsensical