membrane potentials

Which statement accurately describes an action potential?

All action potentials in a single neuron are of the same magnitude (strength).

During an Action Potential, the diffusion of:

Na+ into the cell causes it to depolarize

How does myelination affect the propagation of an action potential?

It speeds propagation by forcing the expression of voltage-gated channels only at the nodes.

Which of the following best describes a neuron at resting membrane potential? A. The inside of a neuron is more negatively charged. B. The outside of a neuron is more negatively charged. C. The inside and the outside of a neuron have the same electrical charge. D. Potassium ions leak into a neuron at rest.

A. The inside of a neuron is more negatively charged.

At resting potential, the ion distribution inside and outside of a neuron is such that __________ ions are most abundant on the outside of the cell, while __________ ions are most abundant on the inside of the cell. A. potassium; sodium B. sodium; potassium C. calcium; phosphate D. sulfate; potassium

B. sodium; potassium

Which of the following statements is True? A. The intracellular Na+ concentration is higher than the extracellular Na+ concentration. B. The intracellular K+ concentration is lower than the extracellular K+ concentration. C. A resting membrane potential of ‐70 mV is mainly due to diffusion of Na+ into the cell. D. The resting membrane potential is closer to potassium equilibrium potential than to sodium equilibrium potential.

D. The resting membrane potential is closer to potassium equilibrium potential than to sodium equilibrium potential.

At what phase of the action potential does the opening of the sodium gates play an important role?

Depolarization

During the depolarization phase of an Action Potential:

Na+ moves into the cell

The distribution of sodium and potassium ions across the membrane of an axon is created and maintained by

active transport

Resting potential in a neuron is maintained by

active transport.

The all‐or‐none principle states that

all stimuli large enough to bring the membrane to threshold potential will produce identical action potentials.

A common feature of action potentials is that they

are triggered by a depolarization that reaches threshold.

Why are action potentials usually conducted in one direction?

The brief refractory period prevents reopening of voltage-gated Na+ channels

What happens when a resting neuron's membrane depolarizes?

The neuron's membrane voltage becomes less negative or more positive.

Increasing the intensity of a stimulus to a nerve cell beyond the threshold level causes:

more action potentials

The resting membrane potential has a negative charge on the inside of the cell. The most DIRECT contributor of this positive charge is the:

movement of K+ out of the cell

In a resting state, the plasma membrane of a neuron is

polarized

Depolarization of a nerve cell is caused by

sodium ions entering the cell.

During the repolarization phase of an Action Potential:

the inside of the cell becomes more negative

During repolarization phase of action potential:

the membrane potential goes from +30 mV to ‐70 mV

Action potentials occur when _____________.

the membrane potential reaches the threshold potential

During an action potential

the rising phase is due to an influx of Na+ and the falling phase is due to an efflux of K+

In the resting state, the electrical polarity inside a cell is negative PRIMARILY because:

there is concentration gradient for K and there are leak K channels

The "threshold potential" of an excitable cell is the:

voltage at which the inflow of Na+ causes an explosive depolarization of the membrane

Ion channels in a cell membrane that open in response to changes in membrane potential are called _______channels.

voltage‐gated

In response to a stimulus, if the membrane potential becomes more negative than the resting potential, we say the membrane is _______________.

Hyperpolarized

Select the incorrect statement about nerve impulse conduction

The strength of impulses carried along a single nerve fiber can vary with the strength of their stimulus.

Graded membrane potentials

decrease in strength when it travels.

When a cell is stimulated and more negative charges flow into the cell so that the cell becomes more negative than the resting membrane potential, this phenomenon describes

hyperpolarization

Saltatory conduction

is faster than conduction on an unmyelinated axon.

The resting potential of a neuron is due mostly to:

leak K+ channels.