Chapter 7

Given a cation with an equilibrium potential of -55 mV, if the plasma membrane of the cell is permeable only to this ion, then which of the following best describes the resting membrane potential?

-55 mV

What equation is used to calculate the membrane potential based on ion concentration gradients and permeabilities?

GHK equation

Which of the following statements is FALSE?

Graded potentials and action potentials are all-or-none.

The Na+/K+ pump is called an electrogenic pump because the imbalance between ________.

Na+ out to K+ in leaves the inside of the cell with a net negative charge

The presence of the ________ prevents the dissipation of the concentration gradient for Na +.

Na+/K+ pump

Stimuli A and B are both suprathreshold stimuli that last for one second, but stimulus A is stronger. Which of the following statements is TRUE?

Stimulus A will cause a higher frequency of action potentials.

Toward the end of the relative refractory period, the continued decrease in stimulus intensity required to initiate an action potential is caused by ________.

decreased potassium permeability

The ________ in graded potential that occurs as current spreads along the membrane happens as a consequence of the ________ of current across the membrane.

decrement : leakage

A change in a cellʹs membrane potential, such that it becomes more positive, is referred to as a ________.

depolarization

Which of the following changes in membrane potential is considered excitatory?

depolarization only

Which of the following axons would have the fastest conduction velocity?

diameter = 20 microns, myelinated

For an unmyelinated axon, conduction velocity is primarily determined by the ________

diameter of the axon

During which of the following states are the majority of voltage-gated sodium channels closed and incapable of opening?

during the absolute refractory period

The spread of voltage by passive charge movement is called ________.

electrotonic conduction

Which of the structures below lacks voltage-gated ion channels responsible for the production of action potentials?

epithelial cell membrane

The membrane potential at which there is no net flux of an ion across the membrane is called that ionʹs ________.

equilibrium potential

Which of the following terms is NOT used to describe a bundle of axons in the central or peripheral nervous system?

ganglia

Membrane permeability is altered in the short term (milliseconds to seconds) by changes in the ________ of ion channels.

gating

A ________ is a subthreshold change in membrane potential within the cell body that decays as it travels away from its point of origin.

graded potential

A change in a cellʹs membrane potential, such that it becomes more negative, is referred to as a ________.

hyperpolarization

In order for a neuron to move from the absolute to the relative refractory period, a majority of that neuronʹs sodium channels must have their ________.

inactivation gates open

The opening of sodium channels causes a rapid ________ of sodium that ________ the neuronʹs membrane

influx : depolarizes

For the sodium channel to open and allow sodium into the cell, ________.

the activation and inactivation gates must both be open

Why will the magnitude of an action potential never reach sodiumʹs equilibrium potential?

the inward movement of sodium is countered by the outward movement of potassium

The direction of change in membrane potential, in response to a stimulus that initiates a graded potential, is dependent upon ________.

the ion channels that are opened or closed

Which of the following characteristics of an action potential does NOT result directly from the refractory period?

the peak level of depolarization reached

As an action potential is propagated away from the axon hillock, why does propagation continue in one direction?

the region just behind the action potential is in the absolute refractory period

The patterns of change in ion channel permeability that occur during an action potential are due to ________ gating of voltage-sensitive potassium and sodium channels

time-dependent

Which of the following cells is NOT classified as a glial cell?

ventricular cells

What percentage of people with diabetes develop peripheral neuropathy?

30

What percentage of people with neuropathy have it secondary to diabetes?

30

Which of the following statements about sodium is FALSE

At the potassium equilibrium potential, there is an electrical force driving sodium ions out of the cell.

Which of the following best describes the electrochemical forces acting on sodium and potassium ions at the resting membrane potential?

The force on sodium ions is to move into the cell, and the force on potassium ions is to move out of the cell.

Why do the distributions of sodium and potassium ions across the plasma membrane of neurons not change appreciably, even following hundreds of action potentials?

The movement of sodium and potassium ions that occurs during an action potential is countered by the active transport of these ions by the Na+/K+ pump.

Which of the following accurately describes afferent neurons?

They transmit information from the periphery to the CNS

Which of the following is an example of spatial summation?

Two stimuli from two sources produce graded potentials on the same neuron at the same time such that the two potentials sum

Which of the following is a functional classification of neurons that, for the most part, are bipolar in structure and carry information from the peripheral axon to the central axon?

afferent neurons

The time between action potentials is directly determined by the ________ the graded potential at the axon hillock

amplitude of

If, under resting conditions, the membrane is much more permeable to sodium than potassium, what would happen to the resting membrane potential?

approach sodiumʹs equilibrium potential

Which of the following does NOT produce graded potentials?

arrival of a suprathreshold stimulus at the axon hillock

On what portion of the neuron do action potentials propagate?

axon

If the graded potential remains above threshold once it reaches the ________, an action potential will be generated.

axon hillock

In a neuron, where is the greatest concentration of voltage-gated sodium and voltage-gated potassium channels?

axon hillock

An action potential originates at the ________ and travels along the axon until it reaches the ________.

axon hillock : axon terminal

In a neuron, where are voltage-gated calcium channels located?

axon terminal

Which of the following is located in the autonomic nervous system?

both sympathetic and parasympathetic nervous systems

Which of the following correctly lists the components of the central nervous system?

brain and spinal cord

As a membraneʹs permeability to a particular ion increases, membrane potential will move ________ that ionʹs ________.

closer to : equilibrium potential

What terminates the positive feedback loop that is involved in the generation of an action potential?

closure of inactivation gates on sodium channels

The repolarization phase of the action potential in a neuron is driven by the ________.

closure of sodium channels and opening of potassium channels

Which of the following is NOT a factor involved in the determination of resting membrane potential?

concentration of sodium receptors

What is the inverse of resistance?

conductance

The opening of an ion channel increases a cell membraneʹs ________, whereas ________ will decrease.

conductance : resistance

Which of the following is the correct term for the movement of an electrical charge across a membrane?

current

At the resting membrane potential, the electrochemical gradient for sodium across the membrane is such that the net flux for sodium movement is directed ________, thereby causing the cellʹs membrane potential to become more ________.

inward : positive

Which of the following determines the resistance to an ionʹs movement across a membrane?

ion channels within the membrane

What type of ion channels in the membrane of neurons allow ions to move across the membrane at rest and thereby contribute to resting membrane potential?

leak channels

What type of ion channels in the membrane of neurons open or close in response to a neurotransmitter binding to its receptor?

ligand-gated channels

Why is the electrical potential of a membrane at rest closest to potassiumʹs equilibrium potential than to sodiumʹs equilibrium potential?

more potassium channels are open, allowing more potassium to move out of the cell

What is the structural classification of a neuron composed of a single axon and a number of dendritic projections from the nerve cell body?

multipolar

What is the functional unit of the nervous system?

neuron

Information is transmitted from cell to cell across the chemical synapse via a(n) ________.

neurotransmitter

In myelinated nerve fibers, where do action potentials occur?

nodes of ranvier

What type of cell enhances the velocity of electrical transmission of an action potential along an axon in the central nervous system?

oligiodendrocyte

The all-or-none principle, associated with the action potential, states that ________.

once membrane potential reaches threshold, an action potential will be generated and that action potential will always be the same magnitude

The regenerative nature of a sodium channelʹs activation gate refers to the situation where an activation gate opens causing a depolarization that triggers which of the following?

opening of other sodium channelsʹ activation gates

The depolarization phase of the action potential is generated by a rapid ________.

opening of sodium channels

Which of the following events is fastest?

opening sodium activation gates

In order to generate an action potential, the magnitude of the inward sodium current must be large enough to overcome which of the following?

outward potassium current

The fact that a cell has an electrical potential difference across its membrane makes that cell ________.

polarized

At the resting membrane potential, the membrane is most permeable to ________, which moves ________ the cell due to its electrochemical gradient.

potassium : out of

The repolarization phase of action potentials in neurons is due primarily to ________.

potassium flow out of the cell

The stimulus intensity required to initiate an action potential is ________ through the course of the relative refractory period.

progressively reduced

Which of the following characteristics does NOT describe an action potential?

rapid increase in potassium permeability

Which of the following best describes the function of the myelin sheath?

reduce a membraneʹs ion permeability

The jumping of an action potential from node-to-node is called ________.

saltitory conduction

The stimulation of an inadequate number of sodium channels for the generation of a positive sodium channel feedback loop is considered a ________ stimulus.

subthreshold