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Neuronal Physiology
A. Multiple Choice
Key/
Page
No.
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a. ability of a cell membrane to conduct an electrical impulse
b. separation of charges across a biological membrane.
c. ability of a membrane to give rise to vesicles.
d. ability of a cell membrane to transport Na+ and K+ ions
e. ability of the plasma membrane to form T-tubules.
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membrane.
a. leak channels.
b. voltage-gated channels.
c. ligand-gated channels.
d. stretch-activated channels.
e. phosphorylation-dependent channels.
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F 4-8
a. when there is an increase in transmembrane potential.
b. if positive ions such as Ca2+ ions leak into the neuron.
c. if there is a decrease in number of intracellular potassium ions.
d. if positive ions such as Ca2+ ions leak into the neuron or when there is an increase
in transmembrane potential.
e. if there is a decrease in number of intracellular potassium ions or when there is an
increase in transmembrane potential .
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following factors is NOT constant during voltage-clamp operations?
a. current
b. membrane potential
c. equilibrium potential
d. None of these answers the question.
b
In the nervous system, the term membrane potential refers to the
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113
a. They exhibit an “all–or-none” character.
b. Their magnitude is related to the intensity of the stimulus that elicits them.
c. They spread by active conductance.
d. They occur only in axons.
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a. ion pumps which drive current flow run out of energy (ATP) as they drift from
the stimulus site.
b. current leakage across the membrane attenuates current available for intracellular
current flow.
c. as it gets away from the active zone, the membrane fluidity decreases and
prevents influx of booster current.
d. of all of these reasons.
e. of none of these reasons.
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a. decreasing longitudinal resistance.
b. increasing longitudinal resistance.
c. decreasing membrane resistance.
d. increasing membrane resistance.
e. increasing capacitance.
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9.
a. typically between –50 mV and –55 mV.
b. typically 10 mV to 15 mV higher than resting potential.
c. the membrane potential at which a graded potential is converted to an action
potential.
d. all of these.
e. none of these.
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F 4-8
channel is in which conformation?
a. closed but capable of opening
b. open, or activated
c. closed and not capable of opening
d. activation gate open; inactivation gate closed
e. activation gate closed; inactivation gate closed
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F 4-8
a. greater than it was at rest.
b. greater than its permeability to K+.
c. increased due to activation of voltage-gated Na+ channels.
d. all of these.
e. none of these.
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resulting in an electrical signal?
a. opening of voltage-gated ion channels
b. changes in membrane permeability in response to a stimulus
c. closing of voltage-gated ion channels
d. a change in the movement of ions through leak channels
e. closing of voltage-gated potassium channels
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a. the dendrites
b. the cell body
c. the axon hillock
d. the axon
e. the axon terminal.
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in which conformation?
a. closed but capable of opening
b. open, or activated
c. closed and not capable of opening
d. Any of these.
e. None of these.
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inactivation gate but which is otherwise normal. This neuron would be expected to
a. conduct action potentials bidirectionally.
b. lack an absolute refractory period.
c. lack a relative refractory period.
d. all of these.
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a. the amplitude (height) of the action potential with stronger stimuli eliciting taller
action potentials.
b. duration of a single action potential with stronger stimuli eliciting overshoots
with more area under the curve.
c. frequency of action potentials with stronger stimuli eliciting higher frequencies.
d. faster conduction velocities with stronger stimuli resulting in more rapid
depolarization of contiguous segments of the axonal membrane.
e. all of these.
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the nervous system by .
a. central, Schwann cells, peripheral, oligodendrocytes
b. vertebrate, Schwann cells, invertebrate, oligodendrocytes
c. central, oligodendrocytes, peripheral, Schwann cells
d. vertebrate, oligodendrocytes, invertebrate, Schwann cells
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129
of conduction of action potentials by decreasing the longitudinal resistance of the axon?
a. increasing the number of channels in the plasma membrane
b. myelinating the axon
c. increasing the diameter of the axon
d. placing all voltage-gated ion channels at distant intervals
e. None of these.
of conduction of action potentials by increasing the membrane resistance of the axon?
a. increasing the number of channels in the plasma membrane
b. myelinating the axon
c. increasing the diameter of the axon
d. placing all voltage-gated ion channels at distant intervals
e. decreasing the number of channels in the membrane.
e
Neurotransmitters are
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a. chemical messengers used at chemical synapses.
b. found in synaptic vesicles in the synaptic knob.
c. released in response to elevated calcium in the axon terminal.
d. able to bind to receptors on the post-synaptic cell.
e. All of these.
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F 4-16
neuron a suprathreshold stimulus and then perform an assay to test whether
neurotransmitter is released into the medium. Which of the following outcomes would
you predict?
a. No neurotransmitter is detected since influx of calcium into the synaptic knob is
required for neurotransmitter release.
b. No neurotransmitter is detected since influx of calcium is required in order for
the neuron to conduct an action potential.
c. Neurotransmitter is detected since calcium is not required for action potential
conduction and the initial stimulus was suprathreshold.
d. We cannot predict the outcome without knowing whether the neuron was
myelinated.
e. None of these.
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132
normally be the postsynaptic neuron to the presynaptic neuron), would an action
potential be conducted in a retrograde direction (along the axon toward the cell body)?
a. Yes.
b. No, since the normally presynaptic neuron lacks receptors for the ions carrying
current from the normally postsynaptic neuron.
c. No, since the normally presynaptic neuron would be refractory to retrograde
conduction.
d. No, unless the concentration gradients for all the relevant ions were reversed.
e. No, since there’s no axon hillock at the axon terminal of the normally presynaptic
neuron.
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a. leak channels and nongated channels
b. gated channels and triggering event
c. chemically gated channels and ligand gated channels
d. mechanically gated channel and stretch activated channels
e. graded potentials and leak channels
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a. The lower the resistance the lower the current flow between two regions of an
axon.
b. The lower the resistance the greater the current flow between two regions of an
axon.
c. Capacitance is a measurement of current flow along an axon.
d. Neurons that rely on electronic flow of current for communication purposes are
noted for their low membrane resistance.
e. None of these statements are true.
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channels in the subsynaptic membrane
a. has no effect on the probability of the postsynaptic cell reaching threshold since
there’s no movement of Cl–.
b. increases the probability of the postsynaptic cell reaching threshold since the
entry of Na+ into the cell (through another route) will make the cell less negative
and allow Cl– to leave the cell, offsetting the effect of Na+.
c. decreases the probability of the postsynaptic cell reaching threshold since the
entry of Na+ into the cell (through another route) will make the cell less negative
and Cl– will enter the cell, offsetting the depolarizing effect of Na+.
d. none of these.
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true?
a. In a resting neuron the electrical gradient for sodium is inward.
b. In a resting neuron the electrical gradient for potassium is inward.
c. In a resting neuron the concentration gradient for sodium is outward.
d. In a resting neuron the concentration gradient for potassium is outward.
e. In a resting neuron, the electrical and concentration gradients for sodium and
potassium result in a membrane potential.
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a. acetylcholine.
b. acetyl CoA.
c. acetic acid.
d. glutamic acid.
e. acetylcholinesterase.
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a. break down acetylcholine at synapses to limit its availability for activating its
receptor.
b. transfer the acetyl group of acetyl CoA to oxaloacetate in the tricarboxylic acid
cycle.
c. import acetylcholine into synaptic vesicles in the nerve endings.
d. transfer the acetyl group of acetyl CoA to choline to generate acetylcholine.
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postsynaptic membrane potential, that phenomenon is known as
summation.
a. temporary
b. temporal
c. lateral
d. spatial
e. grand
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on postsynaptic membrane potential will be
a. no change.
b. a net depolarization since excitation normally triumphs over inhibition.
c. a net hyperpolarization since inhibition normally overwhelms excitation.
d. impossible to predict since we don’t know the relative strength of these synapses.
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a. there is a particularly high density of voltage-gated sodium channels there.
b. threshold potential is lower there than at other sites along the plasma membrane.
c. activation of sodium channels at the axon hillock results in a particularly strong
inward current and consequent depolarization.
d. all of these.
e. none of these.
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true?
a. The duration of a graded potential is related to the duration of the stimulus.
b. Graded potentials can by produced by the net movement of Na+, Cl–, K+ or Ca+
across the plasma membrane.
c. Graded potentials can occur as the result of either hyperpolarization of
depolarization of the plasma membrane.
d. Action potentials show temporal and spatial summation.
e. Action potentials are triggered through the passive spread of membrane
depolarization.
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a. receptors on the presynaptic membrane are activated resulting in a
depolarization of the presynaptic dendrites.
b. acetylcholinesterase levels in a synapse are too high .
c. a postsynaptic cell secretes a signaling molecule that influences the sensitivity of
the presynaptic terminal.
d. enzymes responsible for the breakdown of the neurotransmitter at a synapse are
not produced in sufficient quantity.
e. none of these.
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a. inhibiting phosphodiesterase activity, allowing an accumulation of cAMP and
stimulation of PKA.
b. activating purinergic receptors.
c. inhibiting dopamine reuptake, resulting in prolonged activation of dopamine
receptors by endogenous dopamine.
d. none of these.
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means its primary effect is on which membrane?
a. presynaptic
b. postsynaptic
c. subsynaptic
d. suprasynaptic
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that lives in the deep sea would be expected to have ________ density of Na+-K+ pumps in
their neuronal membranes compared with animals living in shallow water.
a. a higher
b. an equal
c. a lower
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117
a. All cells contain voltage-gated sodium channels.
b. Voltage-gated sodium channels are integral membrane proteins.
c. Voltage-gated sodium channels have roughly equal permeability to Na+ and K+.
d. Voltage-gated sodium channels open in response to any change in membrane
potential.
e. Voltage-gated sodium channels open in response to binding of acetylcholine.
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a. They can be found in annelids and cockroaches.
b. They can be unicellular.
c. They are involved in the coordination of abrupt movements.
d. They were first identified and studied in squid.
e. They may arise as the result of fusion of smaller fibers.
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order for neurons to perform their function?
a. Neurons have to function in reception (e.g. sensory); therefore, they must be able
to switch channels in order to get the appropriate information.
b. The lipid bilayer is impermeable to ions and polar molecules, and ion flow
through the membrane is essential for nervous transmission of information.
c. Channels permit the flow of water through the membrane, and water is necessary
for hydrolysis reactions in the cytoplasm.
d. Channels are required in order to keep Ca2+ levels low inside the cytoplasm.
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symbiotic bacteria residing in them. Interestingly, the pufferfish themselves aren’t
affected by this neurotoxin. The most plausible explanation for the fish’s insensitivity to
TTX is
a. the fish lack neurons.
b. the fish have neurons, but with very short axons that enable them to rely entirely
on electrical conduction based on local passive current flow.
c. the fish lack voltage-gated sodium channels .
d. the fish have voltage-gated sodium channels, but they have a slightly different
sequence from voltage-gated sodium channels found in other organisms, and this
difference affects TTX’s ability to bind the channel.
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neurotransmitter; therefore, one would expect using fluoxetine to result in ___________ in
the post-synaptic neuron.
a. action potentials of greater amplitude to be conducted
b. an increase in the conduction velocity of action potentials
c. graded potentials of lesser amplitude
d. graded potentials of shorter duration
e. graded potentials of longer duration
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B. True and False
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132 delays of as much as 1-2 msec.
133 subsynaptic receipts always leads to the same chain in membrane permeability.
134
134 transmitted in both directions away from the motor end plate.
137 threshold.
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142
144 “closed and not capable” of opening configuration.
111 diffusion of signals to facilitate their movement.
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C. Matching (correct answers are aligned with each number; e.g., #1 matches with letter a)
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D. Essay
Page No.
establishment and conductance of an action potential if a nerve were in an
extracellular solution with a lower than normal level of extracellular potassium
(hypokalemia).
Describe these three synapses and the advantages associated with each.
to be myelinated or unmyelinated, large in diameter or small in diameter? Justify
your answer.
should include a definition of each and an explanation of the ion currents associated
with each.
carried by potassium ions. How must the potassium equilibrium potential compare
to the membrane potential for that to be true? Justify your answer.