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
