Chapter 11

A weak, subthreshold stimulus will result in _______.

Which stimulus was at or above threshold?

Increasing the strength of the stimulus applied to the sensory receptor increased _______.

An excitatory postsynaptic potential occurs _______.

A single action potential is described as _______.

A suprathreshold stimulus results in _______.

A depolarizing synaptic potential is also known as _______.

The stimulus for graded potentials includes _______.

The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____

During depolarization, which gradient(s) move(s) Na+ into the cell?

What is the value for the resting membrane potential for most neurons?

The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?

The concentrations of which two ions are highest outside the cell.

In a neuron, sodium and potassium concentrations are maintained by the sodium-potassium exchange pump such that __________.

The sodium-potassium exchange pump transports potassium and sodium ions in which direction(s)?

Leak channels allow the movement of potassium and sodium ions by what type of membrane transport?

The electrochemical gradient for potassium ions when the transmembrane potential is at the resting potential (-70 mV) is caused by what?

What is the electrochemical gradient of an ion?

In a typical neuron, what is the equilibrium potential for potassium?

The electrochemical gradient for sodium ions in a neuron when the transmembrane potential is at the resting potential is caused by what?

Compared to the electrical gradient for sodium at rest, the electrical gradient for potassium at rest is __________.

In a typical neuron, what is the equilibrium potential for sodium

At rest, why is the transmembrane potential of a neuron (-70 mV) closer to the potassium equilibrium potential (-90 mV) than it is to the sodium equilibrium potential (+66 mV)?

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

The plasma membrane is much more permeable to K+ than to Na+. Why?

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.

What prevents the Na+ and K+ gradients from dissipating?

The channels that provide for the movement of potassium in the resting neuron are _______.

Establishing the resting membrane potential requires energy through the use of the _______.

Which of the following statements about receptor potentials is FALSE?

Which of the following is NOT a functional region of a neuron?

The conducting region of the neuron is the _______.

The typical concentration of sodium is _______.

Which of the following describes a change from the resting membrane potential?

The concentrations of which two ions are highest outside the cell?

Let's consider a scenario in which the resting membrane potential changes from −70 mV to +70 mV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+. The electrical gradient for Na+ would tend to move Na+ __________ while the chemical gradient for Na+ would tend to move Na+ __________.

Sodium (Na+) and potassium (K+) move through the membrane of a neuron because of leak channels. Which of the following is the normal movement of these ions through the leak channels?

An electrochemical gradient causes the movement of Na+ and K+ through the membrane. Which choice best represents the actual forces causing ion movements through the membrane of an undisturbed or resting neuron?

Which of the following is FALSE regarding movement of ions across the membrane when a neuron is at resting potential?

Where in the neuron is an action potential initially generated?

The depolarization phase of an action potential results from the opening of which channels?

The repolarization phase of an action potential results from __________.

Hyperpolarization results from __________.

What is the magnitude (amplitude) of an action potential?

In what part of the neuron does the action potential typically initiate?

During an action potential of a neuron, what directly causes the different channels to open and close?

What is the typical duration of a nerve action potential?

Around what transmembrane potential does threshold commonly occur?

What ion is responsible for the depolarization of the neuron during an action potential?

What type of membrane transport causes the depolarization phase of the action potential in neurons?

During an action potential, after the membrane potential reaches +30 mV, which event(s) primarily affect(s) the membrane potential?

What ion causes repolarization of the neuron during an action potential?

What causes repolarization of the membrane potential during the action potential of a neuron?

What is primarily responsible for the brief hyperpolarization near the end of the action potential?

Where do most action potentials originate?

What opens first in response to a threshold stimulus?

What characterizes depolarization, the first phase of the action potential?

What characterizes repolarization, the second phase of the action potential?

What event triggers the generation of an action potential?

What is the first change to occur in response to a threshold stimulus?

The minimum voltage that is required to generate an action potential is called the _______.

Increasing the voltage resulted in which of the following?

An axon that is more negative than the resting membrane potential is said to be _______.

If an increase in extracellular potassium hyperpolarizes a neuron, which of the following would be correct?

A nerve is _______.

The region on the neuron where action potentials are generated is called the ______.

In this simulation, ___________________ will be used to stimulate the axon.

We describe the regeneration of the action potential down the membrane of the axon of the neuron as _______.

An action potential requires _______.

To reach threshold, the amount of sodium _______.

Which of the following blocks voltage-gated sodium channels?

Which of the following is used to block pain?

Which of the following occurs first in the generation of an action potential?

Which of the following occurs during depolarization?

Which of the following occurs during repolarization?

Which of the following allow the movement of potassium through the neuronal membrane?

The generation of an action potential in a neuron requires the presence what type of membrane channels?

During the action potential, when does sodium permeability initially DECREASE?

During an action potential, the rapid decrease in sodium permeability and simultaneous increase in potassium permeability is responsible for __________.

How is an action potential propagated along an axon?

Why does the action potential only move away from the cell body?

The velocity of the action potential is fastest in which of the following axons?

Action potential propagation begins (is first generated at) what region of a neuron?

Where are action potentials regenerated as they propagate along an unmyelinated axon?

The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold?

In an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction?

Approximately how fast do action potentials propagate in unmyelinated axons in humans?

In contrast to the internodes of a myelinated axon, the nodes __________.

Where are action potentials regenerated as they propagate along a myelinated axon?

The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.

How do action potential propagation speeds in myelinated and unmyelinated axons compare?

Multiple sclerosis (MS) is a disease that stops action potential propagation by destroying the myelin around (normally) myelinated axons. Which of the following best describes how MS stops action potential propagation?

What type of conduction takes place in unmyelinated axons?

An action potential is self-regenerating because __________.

Why does regeneration of the action potential occur in one direction, rather than in two directions?

What is the function of the myelin sheath?

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

In which type of axon will velocity of action potential conduction be the fastest?

Which fibers generate the smallest value for conduction velocity?

The time interval for conduction would be shortest with

Increasing the amount of myelination _______.

In this activity, the stimulus voltage used was _______.

Which of the following is described correctly?

The rate with which an action potential travels along an axon _______.

Which of the following describes a B fiber?

The nodes of Ranvier are _______.

Saltatory propagation occurs in _________ axons, in which action potentials _________.

In a synapse, neurotransmitters are stored in vesicles located in the __________.

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

Binding of the neurotransmitter to its receptor causes the membrane to __________.

The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?

The small space between the sending neuron and the receiving neuron is the

A molecule that carries information across a synaptic cleft is a

When calcium ions enter the synaptic terminal,

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

If a signal from a sending neuron makes the receiving neuron more negative inside,

Calcium and magnesium are both _______.

A synapticcleft, or synaptic gap, can be found between a neuron and ______.

The membrane potential that occurs when neurotransmitters bind to their receptors is called _______.

The release of neurotransmitter occurs _______.

Which of the following occurs first?

Which of the following is an example of a presynaptic cell?

What separates the presynaptic and postsynaptic cells at a chemical synapse?

Which of the following best describes the role of calcium in synaptic activity?

What is the role of neurotransmitter at a chemical synapse?

What mechanism releases neurotransmitter from presynaptic neurons?

What type of channel in the postsynaptic membrane binds neurotransmitter?

What is the primary role of the enzyme acetylcholinesterase (AChE) at a cholinergic synapse?

Events that occur at a cholinergic synapse are listed here, but they are arranged in an incorrect order. Choose the correct order of these events below. (a) Calcium influx triggers exocytosis of ACh. (b) An action potential depolarizes the synaptic terminal. (c) ACh is removed by AChE. (d) ACh binds to receptors on the postsynaptic membrane.

The time interval between action potentials is called the _______.

Increase in stimulus intensity _______.

The frequency of action potentials is _______.

During the relative refractory period, _______.

When the stimulus intensity increases, _______.

At threshold, axons will _______.

Longer stimuli will allow for _______.