CBIO Exam I, Quizzes

During the overshoot phase of an action potential, membrane potential briefly reaches a value near _________mV.

+50

The calcium ________ pumps calcium in a cyclical process that utilizes energy from ATP.

ATPase

The major proponents of the neuron doctrine were

Cajal and Sherrington

The effect of ________ in the CNS can be nullified by IPSPs.

EPSPs

This technique first revealed the tremendous diversity of neuronal cell types by revealing different cell bodies along with their processes.

Golgi stain

Removal of extracellular ______ will disrupt the function of the Na+/K+/ ATPase pump.

K+

How does membrane permeability to K+ and Na+ change during an action potential?

PK exceeds PNa at rest; PNa temporarily increases during the action potential

Mammalian K+ channels have ________ additional structures that act as voltage sensors.

four

Na+ and K+ channels can work ___________ of one another.

independently

In the sequence of events in neurotransmission, what event occurs just after the action potential arrives at the presynaptic terminal?

influx of Ca2+ into the presynaptic terminal

A neuron with multiple, highly branched dendrites and one axon does what?

integrates information from many neurons

Which current is produced in response to a hyperpolarizing stimulus in a giant axon of a squid?

inward capacitative current

The action potential can be reconstructed based entirely on the time course and amplitudes of the ___________________.

ionic conductances

In a two-compartment model of a cell with a K+ and Cl- permeable membrane and a ten-fold excess of K+ inside the compartment, how would the membrane potential change if all K+ ions were replaced by Cl- ions?

it would become positive

Which vesicles, loaded with neuropeptides, arrive in the presynaptic terminal via axonal transport?

large dense core vesicles

A _________________________ is most likely to evoke an action potential.

large depolarizing current pulse

Nodes of Ranvier represent gaps in the _________.

myelin

Most neurons are __________.

polarized

An initial decrease in the ___________ current is not integral to the action potential waveform.

potassium

The part of the synapse to which the contents of synaptic vesicles bind is called the _________.

receptor

Which types of electrical signals occur within the neural circuit for a spinal reflex?

receptor potential, synaptic potential, and action potential

An action potential travels in only one direction along the axon because of its __________ property.

refractory

The neurons whose synaptic connections with glandular cells trigger stomach secretions are located in ________.

the ganglia embedded in the wall of the stomach

At 26mV of membrane potential, this happens

the late outward current decreases in magnitude

At -26mV of membrane potential, this happens

the late outward current increases in magnitude

What phenomenon explains the unidirectional propagation of action potentials?

the presence of a refractory period

In what way are ion channels similar to active transporters?

they are both proteins

What advantage do intracellular recordings have over extracellular ones?

they can record synaptic and receptor potentials

Who proved that chemicals transfer electrical information between neurons?

Loewi

This brain imaging technique uses atoms that behave like small magnets.

MRI

Which glial cell type serves as a resident immune cell in the CNS?

Microglia

_________ is higher outside cells than inside cells

Na

The permeability of what ion is responsible for the rising phase of the action potential?

Na+

Toxin from a scorpion slows the inactivation of ________ channels.

Na+

What ion is transported down its concentration gradient by transporters?

Na+

The ___________________ relates the equilibrium potential of an ion to its intra- and extracellular concentrations.

Nernst equation

Which cell produces myelin in the nerves of the PNS?

Schwann cell

What treatment would prevent the release of a neurotransmitter from the presynaptic terminal?

a toxin that cleaves synaptobrevin

The proteins that establish ionic gradients are called ___________.

active transporters

The amplitude of the action potential of a given neuron is ________________.

always the same

In the knee-jerk reflex, the afferent neurons ________.

are sensory neurons

___________ transmission of electrical signals allows an electrical synapse to synchronize the electrical activity of multiple neurons.

bidirectional

The capability of a nerve terminal to rapidly and dramatically produce very large changes in calcium levels is most dependent on the enormous gradient of ________ across the membrane.

calcium

When current is injected into an axon, the current will _______ exponentially with increasing distance from the injection site, assuming no action potential is present.

decay

________ is the main target for incoming signals received from the axons of other cells

dendrites

A neuron that innervates a large number of other neurons represents ________ neural signaling.

divergent

In a two-compartment model of a cell with a K+ and Ca2+ permeable membrane and a ten-fold excess of K+ inside the compartment, how would the membrane potential change if all K+ ions were replaced by Ca2+ ions?

it would be reduced by half

MEPPs are produced by spontaneous release of a ____________.

neurotransmitter

Where will voltage-gated Na+ channels be most abundant?

nodes of Ranvier

Equilibrium potential is affected by the concentration and electrical gradients of _______, whereas membrane potential is affected by gradients of __________.

one ion; all ions

Small molecule neurotransmitters are _________ for __________.

taken back into the presynaptic terminal; reuse

Which statement about active ion transporters is true?

they move certain ions against the concentration gradient

Under what circumstance is the Goldman equation equivalent to the Nernst equation?

when a membrane is permeable to only one ion

Nerve cells have ________ conductivity compared to copper wires.

worse

Concentration gradients would not be maintained across the membrane if _________ in a neuron stopped functioning.

ATPase pumps

__________ play a role in the formation of the blood-brain barrier.

astrocytes

Why is the resting potential of a cell negative?

at rest there is an excess of K+ inside the cell, but the membrane is permeable to all ions

What is the mechanism of action of most local anesthetics?

block Na+ channels involved in the generation of action potentials

What ligand-gated ion channel is regulated primarily by an intracellular signal?

cAMP and cGMP-gated ion channels

What structure can be found exclusively at an electrical synapse?

connexon

Which part of DNA is transcribed into mRNA?

Exon

What is the source of the quanta that make up the EPP?

fusion of individual synaptic vesicles with the plasma membrane

What type of cell forms nodes of Ranvier in the CNS?

oligodendrocytes

Most neurons have

one axon hillock

What is the net charge transported by one cycle of the Na+/K+ ATPase pump?

one positive charge leaves the cell

During the rising phase, sodium channels are ______ and potassium channels are ______.

open; closed

The application of a intracellular Ca2+ chelator impacts the function of a synapse by eliminating the _______ potential and the _______ dependent vesicle fusion.

postsynaptic; Ca2+

The __________ period ends when the sodium channels are no longer activated.

refractory

What is the role of interneurons in the knee-jerk reflex?

relaxation of flexor muscles

Compared with projection neurons, axons of local circuit neurons are

shorter

When a muscle fiber is held at a voltage of 0mV at the neuromuscular end plate, ACh no longer produces a current because an influx of _______ is balanced by an efflux of ________.

sodium; potassium

At 0mV of membrane potential, this happens

the early current is at its maximum

What do microscopic and macroscopic Na+ currents have in common?

they represent a flow of many ions

The behavior of Na+ channels is _________ dependent.

voltage

In voltage clamp experiments, the early current will disappear if the membrane is clamped at _________mV.

+52

Hodgkin and Katz discovered that the resting membrane potential changes by _________mV per tenfold change in K+ concentration.

+58

The resting membrane potential typically ranges from _______ to _______.

-40mV to -90mV

If the EPP amplitudes range from 0.4mV to 2.0mV, what is most likely the amplitude of the MEPP?

0.4mV

How many connexin subunits form one complete synaptic channel?

12

From which part of the nervous system do cells that innervate neuromuscular junctions originate?

CNS

Most of the genes in the human genome are expressed in the _______.

CNS

This brain imaging technique uses a narrow X-ray beam.

CT

Which brain research method is associated with the greatest safety concerns?

CT

What ion binds to synaptotagmin, causing the plasma membrane to curve which facilitates fusion?

Ca2+

Work done by these two individuals elucidated changes in membrane permeability that underlie an action potential

Hodgkin and Huxley

If the resting membrane potential is higher than normal levels, ________ could be too high in the extracellular solution.

K

In resting nerve cells, the membrane is quite permeable to _________.

K

Concentrations of which ion, inside and outside of a neuron, have the greatest effect on the resting membrane potential?

K+

_______ channels are the least diverse channel type, with only six different types.

K+

What are clustered at the nodes of Ranvier?

K+ and Na+ channels

Membrane potential depolarizes, Na+ channels open, Na+ current increases, ____________.

K+ channels open

The voltage clamp method controls the _________ at any desired level

K+ current

Which types of channels are implicated in inherited forms of epilepsy?

K+, Ca2+, Na+

During the falling phase, _______ ions are moving ______ the cell.

K; out of

What property is characteristic of Na+ channels but not K+ channels?

ability to inactivate

The _______ current flows only in the nodes of Ranvier, unlike the _______ current.

active; passive

An action potential is an ___________ change in the electrical potential across the nerve cell membrane

all or nothing

In the mature CNS, glial stem cells with the properties of astrocytes can give rise to __________, ___________, and ___________.

astrocytes, oligodendrocytes, and neurons

Black widow spider venom is thought to disrupt the functioning of nerve terminals by circumventing the __________ regulated step of exocytosis to promote massive exocytosis.

calcium

You conduct a voltage-clamp experiment in which you hold the presynaptic terminal of a glutamatergic neuron at 0mV. When you treat the terminal with TTX, an inward current is recorded. Which ion and ion channels are responsible for the current you observe?

calcium; voltage gated calcium channels

In which part of a neuron would most of the ER be concentrated?

cell body

Structures that form the voltage sensors of K+ channels are embedded in the __________________.

cell membrane

What technique measures the current that flows through a single ion channel?

cell-attached patch clamp

What type of receptive field is found only in the primary sensory cortex?

center-surround receptive field

Which intracellular component facilitates the processes of endocytosis and exocytosis underlying synaptic communication?

cytoskeleton

An action potential occurs if current injected into a neuron __________ the neuron to reach ________ potential.

depolarizes; threshold

Which of Golgi's contributions enabled Cajal to make observations that suggested nerve cells are discrete entities

development of a staining method based on impregnation with silver salts

The classic voltage clamp technique would be suitable for the ________ measurement of current flowing through the cell membrane.

direct

A scientist wishes to develop a new drug that prevents synaptic communication via neuropeptides but not small molecule neurotransmitters. What mechanism would be a good target?

disruption of axonal transport

Presynaptic and postsynaptic neurons that form _______ synapses are connected via ________.

electrical; gap junctions

Which technique first produced unequivocal support for the neuron doctrine of the nervous system?

electron microscopy of nervous tissue

The set of neurons and small ganglia associated with the digestive tract is called the _______ nervous system.

enteric

_________ occurs during neurotransmitter release into the synaptic cleft.

exocytosis

The K+ channel is made up of ______, each of which contains helical membrane spanning domains with a ________ between them.

four subunits; pore loop

The analysis of coding and regulatory DNA of an individual organism or species is _______________

genomics

The TRP ion channel family includes channels responsive to _______ and ______.

heat and cold

A sustained outward current as a result of ____________ was not observed by Hodgkin and Huxley.

hyperpolarization

How will a neuron respond to an injection of negative current?

hyperpolarization

What is the primary pathophysiological mechanism associated with multiple sclerosis?

immune response within the nervous system

Neuroethology is the field devoted to studying complex behavior ____________.

in the native environment

During the falling phase, sodium channels are ______ and potassium channels are ______.

inactivated; open

During the knee jerk reflex, the role of the spinal interneuron is to ________ the _______ muscle, allowing the leg to _________.

inhibit; flexor; extend

Which method of visualization manifests as a yellow pigment?

intracellular injection of a fluorescent dye

_________ receptors have immediate effects, whereas _________ receptors produce long-term effects.

ionotrophic; metabotrophic

Which substances diffuse through connexon channels between pre and postsynaptic neurons?

ions, second messengers, small proteins, ATP

Which experimental model did Hodgkin and Katz use in their studies of the resting membrane potential?

living squid axon

The synaptic potential ________________________.

makes communication between nerve cells possible

For neurons to communicate electrically, separation of large amounts of electrical charge with excess _________ charges are stored in the cell.

negative

The statement "exocytosis and endocytosis are important for synaptic communication" describes both _________ and ________.

neural and glial cells

What type of substance binds only at the extracellular domain of a ligand-gated ion channel?

neurotransmitter

In a two-compartment model of a cell with a K+ permeable membrane, at K+ equilibrium potential, there is ________ flux of K+ ions.

no net

In a two-compartment model of a cell with a K+ and Na+ permeable membrane and a ten-fold excess of K+ inside the compartment, how would the membrane potential change if all K+ ions were replaced by Na+ ions?

no potential would be generated

In situ hybridization is based on using ________________ to detect specific proteins

nucleic acid probes

What is the major determinant of the permeability of a membrane to a specific ion?

number of open ion channels specific for that ion

What technique should be used to study the effects of the extracellular environment on ion channel activity?

outside-out patch clamp

____________ opens voltage-dependent Na+ channels in the adjacent region of axon.

passive current

Subthreshold current injected into an axon flows _______ along the axon and ______ with distance from the site of injection.

passively; decays

Cognitive neuroscience is concerned with _______, _______, ______, and ______.

perception, emotions, language, and memory

The spinal nerve represents the ____________ nervous system

peripheral

The neurotransmitter at a chemical synapse acts on the receptors in the __________ membrane.

postsynaptic

The application of a Ca2+ channel blocker impacts the function of a synapse by eliminating the _______ potential and the _______ Ca2+ current.

postsynaptic; presynaptic

The _______________ most directly impacts the rate of information processing within the CNS.

propagation speed of action potentials

SNARE proteins participate in vesicle exocytosis by forming a _________ complex that pulls the vesicle membrane against the plasma membrane.

protein

This process of the slow time course of turning off K+ conductance activation and the persistence of Na+ conductance inactivation underlies the __________________.

refractory period

What step of peptide neurotransmitter processing takes place in the presynaptic terminal?

release

What treatment was shown to eliminate the early inward current in squid giant axons?

removal of external sodium

How could you determine that Na+ influx into a cell underlies the early current?

remove Na+

If Na+ channels stay open, it is likely that the membrane would __________.

repolarize

__________ phase of the plasma membrane does not occur during an action potential.

resting

During which phases of an action potential does membrane permeability to Na+ exceed membrane permeability to K+?

rising and overshoot phases

At -10mV, end plate current is _______ in amplitude and directed _______.

small; inward

The degree of depolarization is limited in part by the inactivation time course for the _________ current.

sodium

What is the function of a Schwann cell wrapped in a thick myelin sheath?

speed up conduction of an action potential

A mouse model is created through Cre/lox technology in which a gene is knocked out of the CNS only. Which region would continue to express the gene?

spinal nerves

What two factors are important in determining the membrane potential when there are multiple permeant ions?

the concentration gradient and permeability of the membrane

At 65mV of membrane potential, this happens

the early and late currents flow outward

At 52mV of membrane potential, this happens

the early current reverses its polarity

A dull probe stimulates a Pacinian corpuscle. An electrode is placed midway down the axon, and action potentials are recorded. After one second, the probe is pushed with greater force. What change will occur in the recording?

the frequency of action potentials will increase

In a two-compartment model of a cell with a K+ permeable membrane and a ten-fold excess of K+ inside the compartment, how would K+ ions flow across the membrane?

they would flow from inside to outside

In a two-compartment model of a cell with a K+ permeable membrane and a ten-fold excess of K+ inside the compartment, the membrane potential is experimentally made more negative than the K+ equilibrium potential. How would K+ ions flow across the membrane?

they would flow from outside to inside

The voltage clamp apparatus has ______ electrodes, and the _______ compares the actual membrane potential with the command potential.

three; amplifier

An action potential occurs when the cell's membrane potential reaches __________.

threshold

Which current corresponds to a flow of Na+ in response to a depolarizing stimulus in a giant axon of a squid?

transient inward current

Which function is a characteristic primarily of neurons only, and not glia?

transmitting action potentials

A K+ inward rectifier channel has _____ membrane domains, ______ pore loops, and a _________ sensor.

two; four; voltage

ion channels that are involved in generation of action potentials open or close in response to

voltage

What happens first in the chemical synaptic transmission?

voltage gated Ca2+ channels open

A patient presents with migraines that usually last about 48 hours and are accompanied by vomiting. Two immediate relatives show similar symptoms. What ion channel would you expect to be dysfunctional?

voltage-gated calcium channel

When does electrochemical equilibrium occur?

when the potential across the membrane exactly offsets the concentration gradient

The most important factor determining whether a receptor-operated ion channel is inhibitory or excitatory is ______________________.

whether the permeant ion's reversal potential is positive or negative to threshold

Why is the white matter lighter than gray matter?

white matter is richer in myelin

What technique provides the most direct information about the physical, 3D structure of ion channels?

x-ray crystallography

There is an excess of _______ in the extracellular compartment, relative to the intracellular compartment.

Na+, Cl-, and Ca2+

What transporter plays a key role in maintaining the concentration gradients of ions in the brain that are critical for generating electrical signals?

Na/K ATPase pump

Studies of the ionic basis of the action potential using giant squid axon found that decreasing ______ outside of the cell decreases the size of the __________.

Na; action potential

During the rising phase, _______ ions are moving _____ the cell.

Na; into

Hodgkin and Katz proposed that _______ was the predominant ion associated with the firing of an action potential because the ___________ approaches the Na+ Nernst potential during the _________.

Na; membrane potential; rising phase

What protein plays a key role in endocytosis?

clathrin