P&P1 - Review questions for resting membrane potential and action potentials - Huang

A "less negative" membrane potential means: A. it is "more positive" than the resting potential B. it is a number closer to zero mV C. the resting membrane potential has moved closer to the sodium equilibrium D. All of these statements describe the term "less negative."

All of these statements describe the term "less negative."

Which of the following cells would have a greater electrical attraction for sodium ions to enter the cell? A. Cell with membrane potential = ‐90 mV B. Cell with membrane potential = ‐70 mV C. Cell with membrane potential = ‐50 mV D. Cell with membrane potential = 0 mV E. Cell with membrane potential = +20 mV

Cell with membrane potential = ‐90 mV

The term saltatory conduction refers to: A. "Leaping' of an action potential across a synapse. B. Movement of sodium ions into the cell. C. One‐way conduction of a nerve impulse across a synapse. D. Conduction of a nerve impulse along a myelinated nerve fiber. E. Action of the sodium‐potassium pump during repolarization.

Conduction of a nerve impulse along a myelinated nerve fiber.

A drug for high blood pressure causes extracellular K+ level to decrease from 4.5 mM to 2.5 mM in a particular patient. What is likely to happen to the resting membrane potential of the liver cells of this patient? A. Nothing, because liver cells don't have a resting membrane potential. B. Hyperpolarization. C. Depolarization. D. It becomes less negative. E. It becomes more positive.

Hyperpolarization

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: A. Depolarization B. Repolarization C. Hyperpolarization

Hyperpolarization

What is/are the primary role of the Na/K‐ATPase in establishing the resting membrane potential in a cell? A. It pumps a net positive charge out of the cell creating the resting membrane potential. B. It creates the chemical gradients for sodium and potassium ions. C. It creates the electrical gradients for sodium and potassium ions. D. Both A and C. E. All of above.

It creates the chemical gradients for sodium and potassium ions.

The concentration of Na+ inside a cell changes from 15 mM to 30 mM. The exterior concentration remains at its typical value: 145 mM. What happens to the equilibrium potential of Na+? A. It falls to near zero. B. It decreases somewhat. C. It greatly increases. D. It increases very slightly.

It decreases somewhat

The resting cell membrane potential in cells is primarily affected by the concentration of: A. K+ B. Cl‐ C. Fe+2 D. Na+ E. Ca+2

K+

During an Action Potential, the diffusion of: A. K+ into the cell causes it to depolarize B. Na+ into the cell causes it to depolarize C. K+ out of the cell causes it to depolarize D. Na+ out of the cell causes it to depolarize

Na+ into the cell causes it to depolarize

During the depolarization phase of an Action Potential: A. Na+ and K+ both move out of the cell B. Na+ and K+ both move into the cell C. Na+ moves out of the cell D. Na+ moves into the cell E. K+ moves out of the cell F. K+ moves into the cell G. the inside of the cell becomes more negative

Na+ moves into the cell

What is responsible for initiating the rising phase of the action potential? A. Closing of the K+ channels. B. Opening of the K+ channels. C. Closing of the Na+ channels. D. Opening of the Na+ channels.

Opening of the Na+ channels.

At resting condition, the cell membrane is most permeable to ______. A. Sodium B. Potassium C. Calcium D. Iron

Potassium

The cation found in higher concentration inside than outside the cell is A. Sodium B. Potassium C. Calcium D. Hydrogen

Potassium

Which of the following statements is true about a cell at rest? A. Permeability to sodium is greater than to potassium. B. Sodium ions are leaking into the cell. C. There is a greater electrochemical force for potassium movement. D. A and B E. All of the above

Sodium ions are leaking into the cell.

Which statement about the action potential or nerve impulse is false? A. Only a relatively small number of Na+ and K+ ions actually diffuse across the membrane. B. Each action potential includes both positive and negative feedback loops. C. The Na+/K+ pumps are directly involved in creating the action potential. D. During the action potential, Na+ and K+ total concentrations are not significantly changed. E. Repolarization requires the outward diffusion of K+ ions.

The Na+/K+ pumps are directly involved in creating the action potential.

Which of the following statements is INCORRECT: A. Although all cells have a membrane potential, only a few types of cells, such as neurons and muscle cells, demonstrate the ability to respond to stimulation ‐ a property called excitability or irritability. B. Nernst equation demonstrate that the membrane potential of a cell can be influenced greatly by factors such as a change in the concentration of any involved ion and by a change in the permeability of the membrane to such ions. C. The resting cell membrane is most permeable to potassium ion (K+) so that any increase in the extracellular concentration of potassium ion will rapidly depolarize the cell. D. The Na+/K+ pumps not only act to counter the leakage of ions across the cell membrane but also transports two Na+ out of the cell for every three K+ that it moves into the cell.

The Na+/K+ pumps not only act to counter the leakage of ions across the cell membrane but also transports two Na+ out of the cell for every three K+ that it moves into the cell.

If the concentration of sodium in the extracellular fluid increased, what would happen to the equilibrium potential for sodium? A. The equilibrium potential would stay the same because it is independent of the concentration gradient. B. The equilibrium potential would become more positive. C. The equilibrium potential would become less positive.

The equilibrium potential would become more positive.

Which of the following statements about the Na+/K+ pump is true? A. Na+ is actively transported into the cell. B. K+ is actively transported out of the cell. C. An equal number of Na+ and K+ ions are transported with each cycle of the pump. D. The pumps are constantly active in all cells.

The pumps are constantly active in all cells.

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 of most cells averages ‐70 mV and is closer to potassium equilibrium potential than to sodium equilibrium potential.

The resting membrane potential of most cells averages ‐70 mV and is closer to potassium equilibrium potential than to sodium equilibrium potential.

The extracellular Cl‐ concentration is 105mM and the intracellular Cl‐ concentration is 10.5 mM. If a Cl‐ ion channel in the cell membrane opens: A. Cl‐ moves in B. Cl‐ moves out C. The membrane depolarizes D. The membrane hyperpolarizes E. Both A and D.

A and D Cl‐ moves in The membrane hyperpolarizes

Which of the following ionic movements will result in a cell's depolarization? A. Na+ entry. B. Cl‐ entry. C. K+ entry. D. Ca2+ entry. E. Both A and D.

A and D Na+ entry Ca2+ entry

In the resting state, K+ diffuse out of cells due to: A. A concentration gradient B. An electrical gradient C. both (a) & (b) D. none of the above

A concentration gradient

The all‐or‐none principle states that A. all stimuli of any magnitude will produce identical action potentials. B. all stimuli large enough to bring the membrane to threshold potential will produce identical action potentials. C. the greater the magnitude of the stimulus, the greater the intensity of the action potential. D. only sensory stimuli can activate action potentials. E. only motor stimuli can activate action potentials.

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

An incecrease in the K+ concentration in the ECF: A. causes cells to depolarize B. causes cells to hyperpolarize C. prevents cells from depolarizing D. prevents cells from hyperpolarizing E. none of the above

causes cells to depolarize

The Nernst equation is most often used to estimate the cell's A. resting membrane potential B. osmotic pressure C. threshold potential D. equilibrium potential for Na+ ions or for K+ ions

equilibrium potential for Na+ ions or for K+ ions

In general, the conduction velocity of an Action Potential along a nerve fiber is: A. faster in a large diameter fiber than in smaller diameter fibers B. faster for a suprathreshold stimulus than a threshold stimulus C. is determined by the Electrical Refractory Period of the nerve fiber D. essentially the same in all nerve fibers

faster in a large diameter fiber than in smaller diameter fibers

The term "voltage regulated" means that the membrane: A. gates open and close with changes in the membrane potential B. potential is controlled by the Na+/K+ pumps C. will not respond unless electrically stimulated D. potential can only be seen with an oscilloscope

gates open and close with changes in the membrane potential

When a stimulus of greater strength is applied to a neuron: A. identical action potentials are produced more frequently (more are produced per minute). B. the total amplitude (height) of each action potential increases also. C. the neuron fires a steady barrage of action potentials for a longer duration of time.

identical action potentials are produced more frequently (more are produced per minute)

Saltatory conduction A. occurs only if the myelin sheath is continuous. B. occurs only if nodes of Ranvier are lacking. C. is faster than conduction on an unmyelinated axon. D. is slower than conduction on an unmyelinated axon. E. occurs at the synapse.

is faster than conduction on an unmyelinated axon.

During continuous conduction, A. action potentials move in all directions along an axon. B. action potentials occur at successive nodes along the length of the stimulated axon. C. local currents depolarize adjacent areas of membrane so that action potentials continue to form along the membrane. D. action potentials produce a local current that is strong enough to spread along the length of the axon. E. local potentials produce a continuous outward flow of potassium ions.

local currents depolarize adjacent areas of membrane so that action potentials continue to form along the membrane.

Increasing the intensity of a stimulus to a nerve cell beyond the threshold level causes: A. a larger local response B. a larger action potential C. a faster action potential D. more action potentials E. no change in the cell's response

more action potentials

According to the Nernst equation, if the extracellular K+ concentration became higher than normal, one would expect the voltage across the membrane to: A. move farther from 0 millivolts. B. move closer to 0 millivolts. C. remain unaffected.

move closer to 0 millivolts

The resting membrane potential has a negative charge on the inside of the cell. The most DIRECT contributor of this positive charge is the: A. movement of K+ out of the cell B. movement of Cl‐ into the cell C. action of the Na+/K+‐ATP Pumps D. high permeability of Na+ across the membrane E. movement of Na+ out of the cell

movement of K+ out of the cell

The maximum number of action potentials an excitable cell can conduct in a given period of time is determined by its: A. membrane potential B. diameter C. conduction velocity D. refractory period E. protein concentration

refractory period

During the repolarization phase of an Action Potential: A. the inside of the cell becomes more negative B. the cell becomes less permeable to all ions C. Na+ flows out of the cell D. Na+ flows into the cell E. K+ flows into the cell

the inside of the cell becomes more negative

During repolarization phase of action potential: A. the K+ channels are closed B. voltage‐sensitive Na+ channels open C. the Na+ are pumped back out of the cell D. the membrane potential goes from +30 mV to ‐70 mV E. the membrane potential goes from 0 mV to +30 mV

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

During a short portion of an action potential, a second action potential can be triggered only with a stronger stimulus. This time is called: A. synaptic delay. B. Ranvier redundancy. C. the absolute refractory period. D. the relative refractory period. E. temporal summation.

the relative refractory period.

In the resting state, the electrical polarity inside a cell is negative PRIMARILY because: A. negatively‐charged, non‐diffusing proteins are present at a high concentration inside the neuron B. the concentration of K+ is lower inside the cell than the outside C. there is net movement of Cl‐ into the cell D. the Na+/K+‐ATP Pumps transport more Na+ out of the cell than K+ into the cell E. there is concentration gradient for K and there are leak K channels

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

The most rapid action potentials are conducted on A. thick, myelinated axons. B. thick, unmyelinated axons. C. thin, myelinated axons. D. thin, unmyelinated axons. E. dendrites.

thick, myelinated axons

The critical level to which the membrane potential must be depolarized in order to cause an action potential is called the: A. resting membrane potential B. threshold potential C. excitatory postsynaptic potential D. receptor potential E. electrical refractory period

threshold potential

The "threshold potential" of an excitable cell is the: A. time lag between the activation of a receptor site and the initiation of an Action Potential B. voltage at which the inflow of Na+ causes an explosive depolarization of the membrane C. number of Na+ that enter the cell before the Na+ channels close D. amount of neurotransmitter it takes to cause an Action Potential E. voltage across the resting cell membrane

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. A. voltage‐gated B. leakage C. active transport D. ligand‐gated

voltage‐gated

Using the Nernst equation, the equilibrium potential for Na+ is A. ‐90 mV B. ‐70 mV C. 0 mV D. +60 mV

+60 mV

The threshold potential for generating an Action Potential in excitable cells is typically around _____ mV. A. ‐70 B. ‐50 C. ‐15 D. 0 E. +15

-50

Arrange these action potential events in proper sequence: 1. Membrane depolarization begins. 2. K+ gates begin to open. 3. K+ gates begin to close. 4. Na+ gates begin to open. 5. Na+ gates begin to close. 6. Membrane repolarization begins. A. 1, 2, 4, 3, 5, 6 B. 2, 6, 3, 4, 1, 5 C. 4, 6, 2, 1, 5, 3 D. 1, 4, 2, 5, 6, 3

1, 4, 2, 5, 6, 3

In the Nervous System, the greater the magnitude of a stimulus, the greater the: A. size of the Action Potentials B. frequency of the Action Potentials C. conduction velocity of the Action Potentials D. Local response E. both (b) & (d) above

B and D frequency of the Action Potentials Local response

Which of the following statements is false? A. The intracellular Na+ concentration is lower than the extracellular Na+ concentration. B. The equilibrium potential is a theoretical voltage — that is, it does not occur naturally in living cells. C. A resting membrane potential of ‐70 mV prevents any diffusion of Na+ out of the cell. D. Due the efforts of the Na+/K+ pumps, the resting cell has both Na+ and K+ concentrations in perfect equilibrium across the membrane. E. The resting membrane potential of most cells averages ‐70 mV and should be distinguished from the theoretical equilibrium potentials for sodium (+60 mV) or potassium (‐90 mV) that are calculated to establish the extremes.

Due the efforts of the Na+/K+ pumps, the resting cell has both Na+ and K+ concentrations in perfect equilibrium across the membrane.

Which of the following statements about the conduction velocity of action potentials is FALSE? A. Conduction velocity in the myelinated axon is faster than in unmyelinated axons. B. The thicker the axon, the slower the conduction speed. C. Nodes of Ranvier increase the conduction velocity. D. Saltatory conduction increases the conduction velocity.

The thicker the axon, the slower the conduction speed.

All of the following are true regarding action potentials except: A. According to the all‐or‐none principle, all action potentials fired by a given neuron are of the same strength. B. During depolarization sodium ion gates are open. C. Hyperpolarization occurs as a result of the rapid outflow of potassium ions. D. Once threshold is reached, both sodium ions and potassium ion gates will open, although not necessarily at the same time. E. The threshold of a given neuron varies considerably depending upon the local conditions at the time of measurement.

The threshold of a given neuron varies considerably depending upon the local conditions at the time of measurement.

Which statement about the action potential or nerve impulse is false? A. There are two types of neuron membrane channels for Na+; one type is always open because it lacks gates, whereas the other type has gates that are closed in the resting cell. B. The Na+/K+ pumps are not directly involved in the formation of an action potential; rather they are required to maintain the proper, opposing concentration gradients of these two ions. C. Within a collection of axons, a low intensity stimulus will only activate those few fibers with low thresholds, whereas high intensity stimuli can activate fibers with both low and higher thresholds. D. The absolute refractory period occurs at a time when the Na+ channel is inactivated before it enters its resting state.

There are two types of neuron membrane channels for Na+; one type is always open because it lacks gates, whereas the other type has gates that are closed in the resting cell.

Which statement about the action potential is true? A. There is positive feedback for sodium and potassium channels. B. There is negative feedback for sodium and potassium channels. C. There is positive feedback for sodium channels and negative feedback for potassium channels. D. There is negative feedback for sodium channels and positive feedback for potassium channels. E. None of the above.

There is positive feedback for sodium channels and negative feedback for potassium channels.

Action potentials conducted without decrement means conducted without A. decreasing its velocity B. altering the threshold potential C. decreasing its amplitude

decreasing its amplitude