Module 1.2 Quiz

What action tends to open the sodium gates across a neuron's membrane?​

depolarization of the membrane

When the potential across a membrane reaches threshold, the sodium channels ____.

open to let sodium enter the cell rapidly

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

permeability

The action potential of a neuron depends mostly on what movement of ions?​

sodium ions entering the cell

What is the approximate resting potential of the inside of a neuron's membrane, relative to the outside?​

​-70 millivolts

Which of the following describes selective permeability?​

​Only certain molecules are allowed to cross the membrane freely.

After the peak of an action potential, what prevents sodium ions from continuing to enter the cell?​

​The sodium gates in the membrane close

At what point do the sodium gates begin to close, shutting out further entry of sodium into the cell?​

​at the peak of the action potential

Ordinarily, stimulation of a neuron takes place ____.​

​at the synapse

A drug that blocks the sodium gates of a neuron's membrane will ____.​

​block the action potential

When a membrane is at rest, what attracts sodium ions to the inside of the cell?​

​both an electrical gradient and a concentration gradient

When a neuron is at rest, what is primarily responsible for moving potassium ions into the cell?​

​both the sodium-potassium pump and electrical gradient

The concentration gradient refers to the ____.​

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

The speed of an action potential down an unmyelinated axon is best described as ____.​

​faster in thick axons than in thin ones

What occurs when a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential?​

​hyperpolarization

Under which conditions would the sodium-potassium pump likely be far less effective in creating a concentration gradient?​

​if selective permeability of the membrane did not exist

The function of a myelin sheath is to ____.​

​increase the velocity of transmission along an axon

When a neuron's membrane is at rest, the concentration gradient tends to move sodium ____ the cell and the electrical gradient tends to move it ____ the cell.​

​into; into

Electrical gradients lead to the ____.​

​movement of ions to areas having opposite electrical charges

The resting potential is mainly the result of ____.​

​negatively charged proteins inside the cell

The resting potential of a neuron refers to the ____.​

​net negative charge on the inside of the neuron

According to the all-or-none law, ____.​

​once an axon reaches threshold, the amplitude and velocity of an action potential are nearly equal each time

When a neuron's membrane is at rest, the concentration gradient tends to move potassium ____ the cell and the electrical gradient tends to move it ____ the cell.​

​out of; into

When the neuronal membrane is at rest, the potassium leak channels ____.​

​permit potassium ions to pass slowly

Local anesthetic drugs attach to the sodium channels of the membrane, which ____.​

​prevents sodium ions from entering and stopping action potential

At the peak of the action potential, the electrical gradient of potassium ____.​

​pushes potassium out of the cell

The primary feature of a neuron that prevents the action potential from traveling back from where it just passed is the ____.​

​refractory period

In the normal course of an action potential, ____.​

​sodium remains much more concentrated outside than inside the neuron

The idea that a neuron's membrane is polarized refers to a difference in electrical potential between ____.​

​the inside and the outside of the membrane

What is one major cause for the resting potential of a neuron's membrane?​

​the sodium-potassium pump

The neuron will produce an action potential only if the depolarization exceeds the ____.​

​threshold of excitation.