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.