BIO QUIZ 2 CH. 2

What happens once an action potential starts?

It is regenerated at other points along the axon.

In what way is a myelinated axon that has lost its myelin (through disease) different from an axon that was never myelinated?

It lacks sodium gates along parts of its surface.

Which of the following is NOT true for sodium ions when the cell is at resting potential?

Sodium tends to be driven out of the neuron by the electrical gradient.

Why are local neurons more difficult to study?

They are so small.

The all-or-none law states that:

a neuron produces an action potential of maximal strength, or none at all.

Which group is most likely to suffer from a thiamine deficiency?

alcoholics

In a myelinated axon, where are sodium gates abundant?

at the nodes of Ranvier

A drug that blocks the sodium gates of a neuron's membrane would:

block the action potential.

What are the nodes of Ranvier?

gaps in the myelin sheath

What is the main source of nutrition for vertebrate neurons?

glucose

Under what conditions is it impossible for a stimulus to produce an action potential?

if the membrane is in its absolute refractory period

Hyperpolarization is:

increased polarization.

A local neuron:

is a small neuron with no axon or a very short one.

Which of the following describes selective permeability?

only certain molecules are allowed to cross the membrane freely

If there is a depolarizing effect on a neuron, the result will be that the neuron will fire:

only if it reaches threshold.

Voltage-activated channels are channels for which a change in the voltage across the membrane alters their:

permeability.

What is the difference in voltage called that typically exists between the inside and the outside of a neuron?

resting potential

A drug that decreases the flow of potassium through the potassium gates of the membrane would:

slow the return of the membrane to its resting potential.

Which of the following molecules would be able to passively cross the blood-brain barrier?

small, uncharged molecules

If depolarization is less than the cell's threshold:

sodium crosses the membrane only slightly more than usual.

The selectivity of a neuron membrane is analogous to:

the blood-brain barrier

The concentration gradient refers to:

the difference in distribution for various ions between the inside and outside of the membrane.

Electrical gradients lead to what kind of movements?

the movement of ions to areas having the opposite electrical charges

Which two factors affect the speed of an action potential?

the presence of myelin and the diameter of the axon

When the neuron is at rest, what is responsible for moving sodium ions out of the cell?

the sodium-potassium pump