ANP lab questions

A synaptic cleft, or synaptic gap, can be found between a neuron and ______. another neuron. a gland. a muscle cell.

All of them

Which of the following occurs first? An action potential arrives at the axon terminal. Synaptic vesicles exit by exocytosis. Voltage-gated calcium channels are opened. Extracellular calcium enters the axon terminal.

An action potential arrives at the axon terminal.

Which of the following occurred in the presence of tetrodotoxin?

An action potential was always seen at R1.

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

Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.

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

K+ (potassium)

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

Myelinated axons with the largest diameter

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

Na+ sodium

What effect did decreasing the extracellular sodium have on the resting membrane potential?

Only a small change occurred, because the resting neuron is not very permeable to sodium.

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

Propagation is faster in myelinated axons.

Which of the following is described correctly?

Schwann cells provide the myelination in the peripheral nervous system.

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

Sodium ions are transported out of the cell. Potassium ions are transported into the cell.

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

The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.

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)?

The membrane is much more permeable to potassium ions than to sodium ions.

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

hich of the following occurred in the presence of tetrodotoxin?

The number of action potentials decreased.

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

The previous axonal segment is refractory.

Which of the following statements about receptor potentials is FALSE? The receptor proteins respond to stimuli. The receptor potential is carried by neuroglia. They can trigger an action potential. Odor molecules can act as stimuli.

The receptor potential is carried by neuroglia.

What effect did increasing the extracellular potassium have on the resting membrane potential?

The resting membrane potential became less negative.

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

Voltage-gated sodium channels begin to inactivate (close) and voltage-gated potassium channels begin to open.

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?

Without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes.

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

a chemical gradient going out of the cell and an electrical gradient going into the cell

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

a postsynaptic potential

Which of the following describes a change from the resting membrane potential? a receptor potential an action potential a receptor potential, a synaptic potential or an action potential a synaptic potential

a receptor potential, a synaptic potential or an action potentia

A weak, subthreshold stimulus will result in _______.

a small depolarization at the receiving end of the neuron

What is the typical duration of a nerve action potential?

2 ms

A depolarizing synaptic potential is also known as _______.

an excitatory postsynaptic potential

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

at every segment of the axon

The release of neurotransmitter occurs _______.

at the axon terminal

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

at the nodes

An excitatory postsynaptic potential occurs _______.

at the receiving end of the interneuron

The conducting region of the neuron is the _______

axon

A nerve is _______.

bundle of axons

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

channel-mediated diffusion

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

chemical and electrical gradients both going into the cell

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

conduction or propagation

What type of conduction takes place in unmyelinated axons?

continuous conduction

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

have lower membrane resistance to ion movement

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

hyperpolarized

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

in the same direction and of the same magnitude.

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

initial segment

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

initial segment of the axon

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

ion channels in the plasma membrane of the receiving neuron open.

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

is called the conduction velocity and is measured in meters/sec

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

leakage

Which of the following is used to block pain?

lidocaine

In the presence of lidocaine, the action potential was NOT affected at R1 because _______.

lidocaine was applied downstream of R1

The nodes of Ranvier are _______.

locations on the axon where the myelin sheath is absent

The typical concentration of sodium is

lower than potassium intracellularly.

Which of the following describes a B fiber?

medium diameter, lightly myelinated

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

medullary region

A suprathreshold stimulus results in _______.

more action potentials

A molecule that carries information across a synaptic cleft is a

neurotransmitter

Increasing the voltage resulted in which of the following?

no change to the action potential

A single action potential is described as _______.

no graded

When the calcium was removed from the extracellular solution, _______.

no neurotransmitter was released

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

potassium efflux (leaving the cell)

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

saltatory propagation

The stimulus for graded potentials includes _______.

sensory stimuli and neurotransmitter

The effects of lidocaine and tetrodotoxin were _______.

similar, but tetrodotoxin had a greater effect

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

sodium (Na+)

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

sodium-potassium pump

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

synaptic cleft

Which of the following blocks voltage-gated sodium channels?

tetrodotoxin and lidocaine

At a chemical synapse, the intensity of the stimulus is coded by _______.

the amount of neurotransmitter released and the amount of calcium that enters the axon terminal

When magnesium was added to the extracellular solution, _______.

the amount of neurotransmitter released decreased

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

the frequency of action potentials in the sensory neuron, the amount of neurotransmitter released at the axon terminal of the sensory neuron and the frequency of action potentials in the interneuron

The time interval for conduction would be shortest with

the largest and most heavily myelinated axons

Which stimulus was at or above threshold?

the moderate and strong stimuli

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

the receiving neuron is less likely to generate an action potential.

In this activity, the stimulus voltage used was _______.

the same for all of the axons and suprathreshold for all of the axons

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

the sodium concentration is higher outside the cell than inside the cell and the potassium concentration is higher inside the cell than outside the cell.

What is the electrochemical gradient of an ion?

the sum of the electrical and chemical gradients for that ion

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

the transmembrane potential (voltage)

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

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

threshold voltage

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

trigger zone

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

voltage

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

voltage-gated potassium channels taking some time to close in response to the negative membrane potential

An action potential requires _______.

voltage-gated sodium channels to open and sodium to flow with its electrochemical gradient

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

would change the membrane potential to a less negative value.

To reach threshold, the amount of sodium _______.

entering the cell must overcome the potassium exiting

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

+66mV

Around what transmembrane potential does threshold commonly occur?

-60 mV

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

-90mV

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

1 meter per second

Which fibers generate the smallest value for conduction velocity?

C Fibers

ncreasing the amount of myelination _______.

decreases the time between action potentials

An action potential is self-regenerating because __________.

depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment

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

diffusion

Calcium and magnesium are both _______.

divalent cations