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.
