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When the membrane potential becomes less negative (more positive) then it is said to be _______.
Depolarized
Hyperpolarized
Prepolarized
Unpolarized
Repolarized
depolarized
The _____ gradient, also called the ______ force of an ion depends on the membrane potential and the concentration gradient and valence of that ion.
Chemiosmotic, ionic
Equilibrium, Nernst
Voltage, electromotive
Electrochemical, driving
Membrane, potential
electrochemical, driving
The electrochemical gradient/driving force of an ion equals the _______.
Membrane potential (Vm) times the Nernst potential (Ex)
Combined Nernst potentials (Ex) of all the ions
Membrane potential divided by the Nernst potential (Ex)
Membrane potential (Vm) minus the Nernst potential (Ex)
Membrane potential (Vm) plus the Nernst potential (Ex)
membrane potential (Vm) minus the Nernst potential (Ex)
The driving force on an ion _______ electrical signaling in a neuron.
Stays constant during
Always decreases during
Can increase or decrease depending on the ion and
Always increases during
Cannot be determined during
can increase or decrease depending on the ion and
In a healthy neuron, because the _____ of an ion stays constant, the driving force only changes as the _____ changes.
Charge, concentration gradient
Nernst potential, membrane potential
Electrochemical gradient, ion concentration
All of these answers
Conductance, valence
Nernst potential, membrane potential
Calculate the driving force for Na+ and K+ at the following membrane potentials.
The Ex for Na+ = +60 mV and the Ex for K+ = -84 mV
The resting membrane potential = -67 mV
Remember, driving force equals membrane potential (Vm) minus the Nernst potential (Ex)
==========================================
a) DF for Na+ at membrane potential = 0 mV
b) DF for K+ at resting membrane potential
c) DF for K+ at membrane potential = +60 mV
d) DF for Na+ at membrane potential = -84 mV
e) DF for Na+ at membrane potential = +60 mV
f) DF for Na+ at resting membrane potential
g) DF for K+ at membrane potential = +40 mV
h) DF for K+ at membrane potential = -84 mV
i) DF for Na+ at membrane potential = +40 mV
j) DF for K+ at membrane potential = 0 mV
a) -60 mV (Driving force = membrane potential (0 mV) - Ex of Na+ (+60) = 0 - (+60) = 0 - 60 = -60 mV
b) +17 mV (Driving force = membrane potential (-67 mV) - Ex of K+ (-84) = -67 - (-84) = -67 + 84 = +17 mV
c) +144 mV (Driving force = membrane potential (+60 mV) - Ex of K+ (-84) = +60 - (-84) = +60 + 84 = +144 mV
d) -144 mV (Driving force = membrane potential (-84 mV) - Ex of Na+ (+60) = -84 - (+60) = - 84 - 60 = -144 mV
e) 0 mV (Driving force = membrane potential (+60 mV) - Ex of Na+ (+60) = +60 - (+60) = +60 - 60 = 0 mV
f) -127 mV (Driving force = membrane potential (-67 mV) - Ex of Na+ (+60) = -67 - (+60) = -67 - 60 = -127 mV
g) +124 mV (Driving force = membrane potential (+40 mV) - Ex of K+ (-84) = +40 - (-84) = +40 + 84 = +124 mV
h) 0 mV (Driving force = membrane potential (-84 mV) - Ex of K+ (-84) = -84 - (-84) = -84 + 84 = 0 mV
i) -20 mV (Driving force = membrane potential (+40 mV) - Ex of Na+ (+60) = +40 - (+60) = +40 - 60 = -20 mV
j) +84 mV (Driving force = membrane potential (0 mV) - Ex of K+ (-84) = 0 - (-84) = 0 + 84 = 84 mV
Ions will move across the membrane only if there is a(n) _______ for that ion.
Leak and gated ion channel
Electrochemical gradient/driving force and membrane potential
Concentration gradient and conductance
Chemical gradient and permeability
Electrochemical gradient/driving force and open ion channel
electrochemical gradient/driving force and open ion channel
In signaling, neurons typically rapidly change their membrane potential by ______.
All of these answers
Increasing or decreasing the number of leak channels
Changing their ionic gradients
Opening gated ion channels
Activating active transporters
Opening gated ion channels
____ is the movement of charge across a certain point over time.
Conductance
Current
Electric potential
All of these answers
Resistance
Current
When current flows across a biological membrane, the most significant and rapid effect it produces will be a change in the _______.
Nernst/equilibrium potential
Membrane potential
Concentration gradient
All of these answers
Ionic concentration in the cytoplasm
Membrane potential
Interneurons produce _____ potentials at synapses called EPSPs and IPSPs.
Graded/electrotonic
End plate
Action
Resting membrane
Receptor/generator
Graded/Electrotonic
Which of the following BEST DESCRIBES the equivalent electrical circuit (EEC) of the neuron?
The resistor/conductor is the plasma membrane and ion channels
The current is the movement of water
The wires are the metal ions
The battery is the ion gradient
All of these answers
The resistor/conductor is the plasma membrane and ion channels
Applying Ohm's law (V=iR or i=V/R) to the EEC of the neuron, _______.
All of these answers
R is the resistance and depends on the lipid bilayer and ion channels
V is the driving force
Current = driving force x conductance (g) where g=1/R
i is the current, which is the movement of ions
All of these answers
In neurons, currents can involve the movement of _____.
Anions, cations and electrons
Only cations
Cations and anions
Only electrons
Only anions
Cations and anions (really only ions)
The concentration gradients remain stable even when there is current flow across the membrane because_____.
The number of ions needed to change the membrane potential is only a tiny fraction of the ions in the bulk solution
All of these answers
The number of ions that flow across ion channels is a tiny percentage of the ions in the bulk solution
The active transporters are constantly working
All of these answers
The movement of ions across the membrane can be _____.
All of these answers
Positive (the movement of positive ions out of the cell or the movement of negative ions into the cell)
Out of the cell
Into the cell
Negative (the movement of positive ions into the cell or movement of negative ions out of the cell)
all of these answers
In the EEC of the neuron, the resistor (conductor) is said to be variable because _____.
All of these answers
The membrane is permeable to oxygen
The membrane also acts as a capacitor
Ion channels can be closed or open
The resistance is a variable in Ohm's law
ion channels can be closed or open
In the EEC of the neuron, according to Ohm's law, the current can be changed by changing the ______.
Driving force
Conductance
Membrane potential
All of these answers
Resistance
all of these answers
If a gated Na+ channel was opened at the RMP, the Na+ would _____ the neuron and produce _____ current.
Flow into, negative
Flow out of, positive
Flow into, positive
Be unable to flow into or out of the, no
Flow out of, negative
flow into, negative
RMP is negative, look at the chart
If the driving force for K+ is positive, and a gated K+ channel is opened, the current will be _____.
0
Positive or negative, depending on the ion
Positive and outward
Neutral and balanced
Negative and inward
positive and outward
An electrophysiologist changes the membrane potential, making it very negative (hyperpolarized) to -100 mV. If the Ex for K+ is -84 mV, the driving force for K+ would be -16 mV. If you opened a gated K+ channel at this membrane potential (-100 mV), K+ would flow ___ and produce a ____ current. In this situation, K+ would actually flow against its concentration gradient.
Out, positive
In, positive
Out, negative
In; negative
in; negative
Two important types of currents in the neuron are ______.
Ionic and electronic
Extracellular and intracellular
All of these answers
Transverse and inverse
Transmembrane and axial/internal
transmembrane and axial/internal
In a neuron, the movement of an ion is affected by _____.
The force of chemical diffusion
The electrical (Coulomb) force
All of these answers
Its chemical gradient
The electric field of the membrane potential
all of these answers
When electrical signaling ceases, the membrane potential decreases/decays back to the resting membrane potential with time and distance because ______,
All of these answers
Ions move in solution and along the membrane
The ionic gradients change rapidly in a neuron
The intracellular and extracellular solutions are balanced
The ionic gradients change slowly in a neuron
ions move in solution and along the membrane
For graded potentials, the rate of decay of the membrane potential depends on the _____ constants.
Time and length
Rate and kinetic
Nernst and equilibrium
All of these answers
Ohm and Coulomb
time and length
For long distance signaling, the ______ potential evolved to overcome the decay of passive, graded membrane potentials.
Receptor
Electrochemical
Resting membrane
Action
action
Which of the following is the important reaction for the Ag/AgCl electrode containing KCl to be useful in electrophysiology?
e- = electron
Ag+ + Cl- + e- <----> AgCl + e-
Ag+ + Cl- <----> AgCl
Ag+ + K+ + e- <----> Ag + K+
K+ + Cl- + e- <----> KCl + e-
Ag + Cl- <----> AgCl + e-
Ag + Cl- <----> AgCl + e-
For the Ag/AgCl electrode, in the forward reaction the ____ is oxidized while in the reverse reaction, the ___ is reduced.
Ag+, Ag
Ag, AgCl
Ag, Ag+
Ag, Cl-
Cl-, Ag+
Ag, Ag+
An electrode transforms ___________ (in a wire) into
________ (in solution), and vice versa.
electrons; ions
An intracellular Ag/AgCl two electrode system can be used to _______.
Clamp the membrane potential at a command voltage
Measure the membrane potential
Inject positive or negative current into the cell
Manipulate/change the membrane potential
All of these answers
all of these answers
In the two electrode voltage clamp mode, the membrane potential ______.
Varies as the current varies
Is always depolarized
Is similar to the current
Is unstable
Is held constant (at the command potential) by injecting positive or negative current
is held constant (at the command potential) by injecting positive or negative current
In the two electrode current clamp mode, the membrane potential ______.
Cannot be measured
Always depolarizes
Is free to vary with injected current
Is measured with the stimulating electrode
Is clamped at the command potential
is free to vary with injected current
Ag/AgCl electrodes are used in ______.
All of these answers
Electroencephalograms (EEGs) to measure brain waves
Electrocardiograms to measure heart electrical activity
Intact neurons to measure the membrane potential
all of these answers
The “electrochemical gradient” for an ion is also called the ________.
Electrochemical potential
Steady state gradient
Driving Force
Equilibrium Potential
Membrane Potential
Driving Force
Which of the following is NOT TRUE about the “electrochemical gradient” for an ion? It _______________.
Depends on the charge of the ion and it is always the same sign (positive or negative) as the charge of the ion
Depends on the concentration gradient
Depends on the Nernst/equilibrium potential for the ion
Depends on the electrochemical potential of the ion
Depends on the membrane potential
Depends on the charge of the ion and it is always the same sign (positive or negative) as the charge of the ion
The Nernst potential for Na+ is +60 mV. At the following membrane potentials below, what would be the driving force for Na+ (right)?
-67 mV (RMP)
-30 mV
0 mV
+30 mV
+60 mV
-127 mV (Driving force = membrane potential (-67 mV) - Ex of Na+ (+60) = -67 - (+60) = -67 - 60 = -127 mV
-90 mV (Driving force = membrane potential (-30 mV) - Ex of Na+ (+60) = -30 - (+60) = -30 - 60 = -90 mV
-60 mV (Driving force = membrane potential (0 mV) - Ex of Na+ (+60) = 0 - (+60) = 0 - 60 = -60 mV
+30 mV (Driving force = membrane potential (+30 mV) - Ex of Na+ (+60) = +30 - (+60) = +30 - 60 = -30 mV
0 mV (Driving force = membrane potential (+60 mV) - Ex of Na+ (+60) = +60 - (+60) = +60 - 60 = 0 mV
The Nernst potential for K+ is -84 mV. At the following membrane potentials below, what would be the driving force for K+?
-84 mV
-67 mV (RMP)
-30 mV
0 mV
+30 mV
0 mV (Driving force = membrane potential (-84 mV) - Ex of K+ (-84) = -84 - (-84) = -84 + 84 = 0 mV
+17 mV (Driving force = membrane potential (-67 mV) - Ex of K+ (-84) = -67 - (-84) = - + 84 = +17 mV
+54 mV (Driving force = membrane potential (-30 mV) - Ex of K+ (-84) = -30 - (-84) = -30 + 84 = +54 mV
+84 mV (Driving force = membrane potential (0 mV) - Ex of K+ (-84) = 0 - (-84) = 0 + 84 = +84 mV
+114 mV (Driving force = membrane potential (+30 mV) - Ex of K+ (-84) = +30 - (-84) = +30 + 84 = +114 mV
The Nernst potential for Cl- is -60 mV. At the following membrane potentials below, what would be the driving force for Cl-?
-84 mV
-67 mV
-30 mV
0 mV
+30 mV
-24 mV (Driving force = membrane potential (-84 mV) - Ex of Cl- (-60) = -84 - (-60) = -84 + 60 = -24 mV
-7 mV (Driving force = membrane potential (-67 mV) - Ex of Cl- (-60) = -67 - (-60) = -67 + 60 = -7 mV
+30 mV (Driving force = membrane potential (-30 mV) - Ex of Cl- (-60) = -30 - (-60) = -30 + 60 = +30 mV
+60 mV (Driving force = membrane potential (0 mV) - Ex of Cl- (-60) = 0 - (-60) = 0 + 60 = +60 mV
+90 mV (Driving force = membrane potential (+30 mV) - Ex of Cl- (-60) = +30 - (-84) = +30 + 60 = +90 mV
Ions will always move across the membrane down/along their electrochemical gradient if there is a/an ________________ for that ion.
Leak and gated ion channel
Concentration gradient and Conductance
Primary active transporter
Electrochemical and membrane potential
Driving force and open ion channel
Driving force and open ion channel
Which of the following information do you need to know to determine whether an ion will move into or out of a neuron through an open channel?
The membrane potential
The concentration gradient of the ion
All of these answers
The charge/valence of the ion
The driving force of the ion
All of these answers
At -30 mV, opening a gated Na+ channel, Na+ would flow ________ the neuron and this would be called a _________ current.
Into; negative
Out of; negative
Into; positive
Slowly; 0
Out of; Positive
Into; negative
At -30 mV, opening a gated K+ channel, K+ would flow ______ the neuron and this would be called a ________ current.
Out of; negative
Out of; Positive
Into; positive
Slowly; 0
Into; negative
Out of; Positive
At -30 mV, opening a gated Cl- channel, Cl- would flow ______ the neuron and this would be called a ________ current.
Out of; negative
Into; negative
Slowly; 0
Into; positive
Out of; Positive
Into; positive
In a neuron, if the membrane potential becomes more positive than the Nernst potential for Na+ or more negative than the Nernst potential for K+, and if their ion channels are open, then __________.
The neuron will be at equilibrium
The membrane potential will not affect the driving force
Ions will flow against their chemical/concentration gradients
Ions will not be able to flow across the membrane
The membrane potential will be unstable
Ions will flow against their chemical/concentration gradients
Current is the ______________.
Sum of the voltage, resistance and capacitance
Inverse of conductance
Difference in electrochemical potential between 2 points in a circuit
Movement of charge across a certain point over time
All of these answers
Movement of charge across a certain point over time
Which of the following is NOT TRUE about transmembrane currents? Transmembrane currents ________________________
Involve the movement of cations or anions
Can be negative or positive
Are typically produced by activating the Na+/K+ ATPase
Directly affect the membrane potential
Can be inward or outward
Are typically produced by activating the Na+/K+ ATPase
When current flows across a biological membrane, the most significant and rapid effect it produces will be a change in the _______________.
Membrane potential
Concentration gradient
Nernst/equilibrium potential
Ionic concentration in the cytoplasm
All of these answers
Membrane potential
The bulk concentration gradients in a neuron remain stable, even when the membrane potential changes. Which of the following IS NOT a basis or feature of this?
When ion channels open, only a small fraction of total ions move across the membrane
Gated channels contribute to maintaining the concentration gradients
Movement of only a small fraction of the total ions across the membrane is required to change the membrane potential
The Nernst potentials remain constant
Active transporters work continuously
Gated channels contribute to maintaining the concentration gradients
How does a healthy neuron change its membrane potential?
By activating and increasing the Nernst potentials
By activating and opening gated ion channels
By activating the active transporters
All of these answers
By activating and modulating the driving forces
By activating and opening gated ion channels
Match each component in a typical RC circuit with its analogous component in the equivalent electrical circuit (EEC) of the neuron.
Voltage
Current
Resistor
Wires
Capacitor
Driving Force
Movement of cations and anions
Plasma membrane plus ion channels
Extracellular and intracellular solutions
Plasma membrane
Applying Ohm’s Law to the Equivalent Electrical Circuit of the neuron, current equals ________________
Open ion channels (conductance) divided by the driving force (V)
The plasma membrane resistance (R) divided by the driving force (V)
The driving force (V) divided by open ion channels (conductance)
The driving force (V) times open ion channels (conductance)
The driving force (V) times the plasma membrane resistance (R)
The driving force (V) times open ion channels (conductance)
In the EEC of the neuron, according to Ohm’s Law, the current can be changed (increased or decreased) by changing all of the following EXCEPT the ________.
Resistance
Driving Force
Membrane Potential
Capacitance
Conductance
Capacitance
In the EEC of the neuron, the resistor (or conductor) can change and is said to be variable. This is because ____________.
Active transporters work variably
The permeability of the lipid bilayer can change
All of these answers
The concentration gradients are variable during signaling
Ion channels can be closed or open
Ion channels can be closed or open
In a neuron, in addition to the transmembrane Na+ and K+ currents, there are also _____________ currents when ions flow within the cytoplasm.
Action
Coulomb
Axial/internal
Potential
Electrotonic
Axial/internal
The Ag/AgCl intracellular electrode interconverts ____________ in the solution to ____________ in the wires.
Cl- ions; Cl- ions
Electrons; Cl- ions
Cl- ions; electrons
All of these answers
Electrons; electrons
Cl- ions; electrons
Which of the following is the important reaction for the Ag/Agcl electrode containing [KCl] to be useful in electrophysiology?
e- = electron
Ag + Cl- <——> AgCl + e-
Ag+ + Cl- + e- <——>AgCl + e-
Ag+ + K+ + e- <——> Ag + K+
Ag+ + Cl- <——> AgCl
K+ + Cl- + e- <——> KCl + e-
Ag + Cl- <——> AgCl + e-
For the Ag/AgCl electrode, in the forward reaction, the _______ is oxidized while in the reverse reaction, the _________ is reduced.
Ag, Cl-
Ag, Ag+
Ag, AgCl
Ag+, Ag
Cl-, Ag+
Ag, Ag+
The two electrode Ag/AgCl intracellular electrode system can be used to do all of the following EXCEPT ________________.
Depolarize or hyperpolarize the membrane potential by injecting current
Manipulate/change the membrane potential
Directly measure the membrane current across the membrane
Control and Clamp the membrane potential
Directly measure the membrane potential
Directly measure the membrane current across the membrane
In current clamp mode, a specific amount of __________ is/are injected into the cell and the _____________.
Ions; membrane potential remains closed/clamped
Current; membrane potential is free to vary
All of these answers
Electrons; Membrane potential hyperpolarizes
Potential; current is free to vary
Current; membrane potential is free to vary
In the two electrode voltage clamp mode, the membrane potential ______________.
Is similar to the current
Is held constant (at the command potential) by injecting positive or negative current
Varies as the current and voltage vary
Can become depolarized or hyperpolarized
Is unstable and can’t be measured
Is held constant (at the command potential) by injecting positive or negative current
Neurons can produce graded/electrotonic potentials called _____________.
EPSPs
IPSPs
Receptor potentials
All of these answers
End plate potentials
All of these answers
Inside a neuron, the movement of an ion is affected by all of the following EXCEPT ______________.
The force of chemical diffusion
The electric field of the membrane potential
The electric (Coulomb) force
Its chemical/concentration gradient
The force of Hydrogen-bonding (Hydration)
The force of Hydrogen-bonding (Hydration)
After synaptic signaling stops, the membrane potential rapidly decays/decreases back to the RMP. All of the following are responsible for the decay of the membrane potential EXCEPT the __________.
Coulomb forces between ions
Movement of ions in aqueous solution
Force of osmotic pressure
Force of chemical diffusion
Movement of ions along the membrane
Force of osmotic pressure
For graded potentials, when signaling stops, the rate of decay of the graded membrane potentials depends mainly on the ___________.
All of these answers
Time and length constants
Overall changes in the cytoplasm
Size of the graded potential
RMP
Time and length constants
For long distance signaling, neurons evolved ________ to overcome the passive decay of graded membrane potentials?
Graded potentials
Action Potentials
All of these answers
Larger ion gradients
Leak ion channels
Action Potentials
Ag/AgCl electrodes are used in _______
Electrocardiograms to measure heart electrical activity
Electroencephalograms to measure brain waves
All of these answers
Intact neurons to measure the membrane potential
All of these answers
In addition to being involved in electrical signaling in neurons, the membrane potential has also been implicated in ________ during development
All of these answers
Neuronal differentiation
Neurogenesis and gliogenesis
Neurulation
Gastrulation
Neuronal differentiation
In a neuron, if the membrane potential becomes less positive than the Nernst potential for Na+ or less negative than the Nernst potential for K+, and if their ion channels are open, then __________.
The neuron will be at equilibrium
The membrane potential will not affect the driving force
Ions will flow against their chemical/concentration gradients
Ions will flow with their chemical/concentration gradients
The membrane potential will be unstable
Ions will flow with their chemical/concentration gradients
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