PSYC 233.01 Module 1.2

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

open to let sodium enter the cell rapidly

Which of the following describes selective permeability?​

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

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

​prevents sodium ions from entering and stopping action potential

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

​sodium ions entering the cell

What causes potassium ions to leave the axon just after the peak of the action potential?​

a continuing concentration gradient and the opening of the potassium gates

Ordinarily, stimulation of a neuron takes place ____.​

at the synapse

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

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

block the action potential

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

permeability

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

pushes potassium out of the cell

What occurs when depolarization is less than the cell's threshold?​

​Sodium crosses the membrane only slightly more than usual.

Which of the following describes the transmission of information in a local neuron?​

​The signal decreases in strength as it travels.

The all-or-none law states that ____.​

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

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

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

​depolarization of the membrane

The concentration gradient refers to the ____.​

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

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

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