BIOL 336 Quiz 6
When the membrane is repolarized to negative voltages, K+ channels are (slower/faster) to close
Slower
The Na+/K+-ATPase pump maintains Na+ and K+ concentrations at stable levels in a resting cell. The contribution of the Na+/K+ ATPase pump to creating an electrical gradient is (small/large), however, it maintains the concentration gradients down which the ions diffuse to produce the charge separation.
Small
In living system, electrical gradient are measured on a _____________, not an absolute scale.
relative
A ________________ scale measures the difference in charge between two points using a voltmeter
relative scale
In an excitable cell, the critical value of the membrane potential to which the cell must be depolarized to trigger an action potential is the _______________ ______________(often ~ -55mV in neurons).
threshold potential
Review Slide 27 - 30
Wuv
Neuron and muscle cells typically have resting potential of ______ to ______
-40 to -90mV
Given an extracellular Cl- concentration of 100 mM and an intracellular Cl- concentration of 10 mM, what is the equilibrium potential of a plasma membrane permeable only to Cl- ? (Hint - you do not need a calculator to solve this question.) A. - 61 mV B. - 30.5 mV C. 0 mV D. + 30.5 mV E. + 61 mV
A. - 61 mV
In a cell that is permeable to only one ion, the equilibrium potential (Eion): A. All of the answers are correct B. Is the membrane potential at which the ion has no movement across the membrane. C. Can be calculated using the Nernst equation D. Refers to the membrane potential exactly opposes the concentration gradient of the ion. E. Is the membrane potential at which the ion's chemical and electrical gradients are equal in magnitude and opposite in direction
A. All of the answers are correct
The loss of positive ions from the cell creates an __________________ gradient A. Chemical B. Concentration c. Electrochemical
A. Chemical
The principle extracellular cation is: A.Sodium (Na+) B.Chloride (Cl- ) C.Potassium (K+) D.Calcium (Ca2+)
A.Sodium (Na+)
The membrane is (polarized/depolarized) when its potential becomes less negative (closer to 0).
Depolarized
What would happen to a negatively charged protein in a cell if K+ ions continuously leak out the cell? Would negative charge increase or decrease?
Increase
Unmyelinated axons have (high/low) resistance to current leak because the entire axon membrane is in contact with the extracellular fluid and has ion channels through which current can leak.
Low
A ___________________ can record membrane potential over time. A. Voltmeter B. Recorder
Recorder
In many neurons, the summation of graded potentials is required to initiate action potentials. Is this a true statement?
True
What does the z in the nernst equation represent?
Valence of the ion
An _____________ ____________________ involves counting the number of ions on either side of the plasma membrane.
absolute scale
Voltage-gated ion channels allow excitable membranes to conduct large, rapid changes in membrane potential called ___________ ____________.
action potentials
When the membrane repolarizes, the channel (opens/closes), forcing the inactivation gate back out of the pore and allowing the channel to return to the closed state with no Na+ flux occurring.
closes
Transient changes in the membrane potential from the resting level produce electrical signals and occur in the form of (i) __________ and (ii) _________ __________________.
graded, and action potentials
Na+ channels uniquely have an ________________ ____________ that limits Na+ flux by blocking the channel shortly after depolarization opens it.
inactivation gate
Membrane potentials are generated mainly by the diffusion of ______ and are determined by both the ionic ________________ differences across the membrane and the membrane's relative __________________ to different ions
ions, concentration, and permeability
In myelinated axons, the conduction process is similar to that described previously for an unmyelinated axon, except that it occurs only at the ________ _____ _______________
node of Ranvier
The resting membrane potential is close to the K+ equilibrium potential because there are more (open/close) K+ channels than Na+ channels. Note that these leak channels are distinct from the voltage-gated channels.
open
A __________________ electrode is inserted through the cell membrane into the cytoplasm
recording
A _________________________ electrode is placed in the external bath, which represents the extracellular fluid, and is given a value of 0 millivolts
reference electrode
In living systems, a ______________ is used to measure the difference in charge between two points, that is, using a relative scale.
voltmeter
Separated electrical charges create the potential to do __________, as occurs when charged particles produce an electrical current as they flow down a potential gradient.
work
The fact that a cell has an electrical potential difference across its membrane makes the makes that cell A. Polarized B. Repolarized C. Hyperpolarized D. Polar E. Depolarized
A. Polarized
Write out the nernst equation.
61 [ion]out E = ---------- log --------- z [ion]in
Action potential propagation is faster in myelinated axons. True or False?
True
Both Na+ and K+ channels reversibly change shape in response to membrane potential changes. True or False?
True
In resting cells, the plasma membrane is much (more/less) permeable to K+ than to Na+, so the membrane potential is (close/away) to the K+ equilibrium potential—that is, the inside is negative relative to the outside.
more, close
In reality, an average value for resting potential of a neuron is _______mV. This means that ions other than K+ contribute to the resting potential.
-70mV
Which principle of the four principles you should remember when dealing with electricity in physiological systems is this referring to? The net amount of electrical charge produced in any process is zero. Overall, the human body is electrically neutral.
1. Law of conservation of electrical charges
What are the four principles you should remember when dealing with electricity in physiological systems:
1. Law of conservation of electrical charges 2. Opposite charges attract; like charges repel each other 3. Separating positive charges from negative charges requires energy 4. Conductor versus insulator
The Na+/K+-ATPase pump maintains Na+ and K+ concentrations at stable levels in a resting cell. The Na+/K+ ATPase pump helps to directly establish the membrane potential by moving ___ Na+ out of the cell for every ___ K+ pumped in. Unequal transport of positive ions makes the inside of the cell more negative.
3 and 2
Which principle of the four principles you should remember when dealing with electricity in physiological systems is this referring to? When separated positive and negative charges can move freely toward each other, the material through which they move is called a conductor (egwater). Separated charges cannot move through an insulator (egphospholipid bilayer).
4. Conductor versus insulator
Which of the following statements about the Na+/K+ is FALSE? A. It transports Na+ and K+ in a 1:1 ratio. B. Its activity requires the expenditure of metabolic (cellular) energy C. It is present in neurons. D. It transports Na+ out of the cell and K+ into the cell.
A. It transports Na+ and K+ in a 1:1 ratio.
When potassium exits a neuron during an action potential: A. The inside of the cell loses positive ions and produces a negative charge inside B. The inside of the cell loses positive ions and produces a positive charge inside C. The inside of the cell loses negative ions and produces a negative charge inside D. The inside of the cell loses negative ions and produces a negative charge inside
A. The inside of the cell loses positive ions and produces a negative charge inside
When a neuron is at rest, the K+ ________ gradient favors K+ diffusion out of the cell while the ________ gradient favors K+ diffusion into the cell . A. concentration; electrical B. concentration; concentration C. electrical; electrical D. electrical; concentration
A. concentration; electrical
Eventually, the electrical force attracting K+ into the cell becomes _____________ in magnitude to the chemical concentration gradient driving K+ out of the cell. At that point, the net movement of K+ across the membrane stops A. equal B. Lower C. Zero D. Higher
A. equal
If the sole force acting upon K+ were the concentration gradient, K+ would diffuse out of the cell until the K+ concentration inside and outside the cell was ________ A. equal B. Lower C. Zero D. Higher
A. equal
By convention, when measuring the difference in charge across a plasma membrane, the extracellular fluid is designated as the ground and is assigned a charge of ___ mV A.) 0 B.) -70 mV C.) +60 mV D.) -60 mV
A.) 0
The ______________ refractory period occurs when voltage-gated Na+ channels are already open or have proceeded to the inactivated state. The inactivation gate has blocked these channels and must be removed by membrane repolarization, closing the pore before channels can reopen to the second stimulus. A.) Absolute B.) Relative
A.) Absolute
The _______________ potential (Eion) is the membrane potential that exactly opposes the concentration gradient of a given ion. The ______________________ potential for a cell permeable to only one ion can be calculated using the Nernst equation, given the concentration of that ion inside and outside the cell. A.) Equilibrium potential B.) Membrane potential C.) Shepard's potential D.) Nernst potential
A.) Equilibrium potential
The membrane potential that exactly opposes the concentration gradient of the ion is known as the _________________ _________________ (Eion) A.) Equilibrium potential B.) Concentration potential C.) Shepard's potential D.) Beck's potential
A.) Equilibrium potential
When a depolarized membrane returns toward the resting value, it is _______________. A.) Repolarization B.) Overshoot C.) Depolarization D.) Hyperpolarization
A.) Repolarization
The membrane depolarization at the trigger zone opens voltage-gated Na+ channels to allow Na+ to enter the axon, causing further membrane _______________________2. A.) depolarization B.) repolarization C.) hyperpolarization D.) overshoot
A.) depolarization
An action potential is generated in the neuronal trigger zone by the summation of ___________________ graded potentials, generated in the cell body and dendrites, that raises the membrane potential above the threshold value (typically -55mV). A.) depolarizing B.) repolarizing C.) hyperpolarizing D.) overshoot
A.) depolarizing
In response to a stimulus, if the membrane potential becomes more negative than the resting potential, we say the membrane is _______. A.hyperpolarized B.depolarized C.unpolarized D.none of the above
A.hyperpolarized
While (all/many/some) cells can conduct graded potentials, only the excitable membranes of neurons, muscle cells, and some endocrine, immune, and reproductive cells have membranes capable of producing action potentials.
ALL
A second stimulus will not produce a second action potential during the _________________ refractory period. A.) Absolute B.) Relative
Absolute
Changes in membrane potential begin in the neuronal trigger zone and are propagated along the axon. Is this a graded or action potential?
Action Potential
An (action/threshold) potential is a rapid change in the membrane potential during which the membrane rapidly depolarizes and repolarizes. Action potentials provide long-distance transmission of information through the nervous system
Action potential
Hyperkalemia is a condition where extracellular potassium is higher than normal. A. Hyperkalemia increases the probability that an action potential will be triggered because the Action Potential threshold is more negative. B. Hyperkalemia causes the resisting membrane potential to be more positive because the driving force on the movement of potassium through leak channels is shifted C. Hyperkalemia causes the resting membrane potential to be more negative the equilibrium potential for potassium is more negative D. Hyperkalemia causes the resisting membrane potential to be more negative because more voltage-gated potassium channels are open.
B. Hyperkalemia causes the resisting membrane potential to be more positive because the driving force on the movement of potassium through leak channels is shifted
In response to a stimulus, if the membrane potential becomes more negative than the resting potential, we say the membrane is _______________. A. None of these are correct B. Hyperpolarized C. Depolarized D. Unpolarized
B. Hyperpolarized
Imagine an artificial cell with a plasma membrane permeable only to Na+ due to the presence of a Na+ leak channel in the plasma membrane. The artificial cell rests in a buffer with a [Na+] of 150 mM. If intracellular [Na+] of this cell is 15 mM, what is the net direction of Na+ cation movement when the electrical potential of the plasma membrane is at the equilibrium membrane is at the equilibrium potential (ENa+) A. Na+ net movement will alternate between a large amount of flow from the inside to the outside of the cell, to a large amount of flow from the outside to the inside of the cell. B. There will be no net direction of Na+ cation movement C. The net direction of Na+ movement will flow from the outside to the inside of the cell. D. The net direction of Na+ movement will flow from the inside to the outside of the cell. E. Na+ net movement will alternate between a large amount of flow from the outside to the inside of the cell, to a large amount of flow from the inside to the outside of the cell.
B. There will be no net direction of Na+ cation movement
An action potential does not re-stimulate the adjacent membrane that was previously depolarized because: A. it is impossible for an action potential to be propagated along an axon toward the neuronal cell body. B. that area of the plasma membrane is in the absolute refractory period. C. the resting membrane potential of the axon is too positive. D. the resting membrane potential of the axon is too negative
B. that area of the plasma membrane is in the absolute refractory period.
The puffer fish, an expensive gourmet delicacy in Japanese cuisine, produces a potent neurotoxin called Tetrodotoxin (TTX). A chef must remove the tissues that produce TTX carefully before serving. TTX blocks the channel openings of voltage-gated Na+ channels. Which of the following is directly inhibited by TTX when ingested? A. the membrane hyperpolarization at the end of an action potential. B. the rapid membrane depolarization of an action potential caused by Na+ entry. C. the outward K+ current of an action potential repolarizing the membrane. D. the entry of Na+ through ligand-gated channels that generate excitatory graded potentials.
B. the rapid membrane depolarization of an action potential caused by Na+ entry.
Given an extracellular Cl- concentration of 100 mM and an intracellular Cl- concentration of 10 mM, what is the net direction of movement of Cl- across a membrane permeable only to Cl- when the membrane is at the equilibrium potential? At the equilibrium potential: A. there is a net outward flow of Cl- across the plasma membrane. B. there is no net direction of movement of Cl- across the plasma membrane. C. there is a net inward flow of Cl- across the plasma membrane. D. an initial net outward flow of Cl- is followed by a net inward flow of Cl-
B. there is no net direction of movement of Cl- across the plasma membrane.
If a motor neuron was stimulated by a current injection electrode to the threshold value about midway along the length of the axon: A. no action potential would be initiated. B. two action potentials would be initiated, one propagated toward the axon terminal and one propagated back toward the axon hillock. C. a single action potential would be initiated and be propagated back toward the axon hillock. D. a single action potential would be initiated but would die out before reaching the axon terminal. E. a single action potential would be initiated and be propagated toward the axon termina
B. two action potentials would be initiated, one propagated toward the axon terminal and one propagated back toward the axon hillock.
Action potential propagation along a myelinated axon. Each node has a high concentration of voltage-gated _______ channels, that open with depolarization and allow Na+ into the axon A.) cAMP B.) Na+ C.) K+ D.) Cl-
B.) Na+
Which of the following terms refers to a reversal of the membrane potential resulting in the inside of a cell becoming positive relative to the outside? A.) Polarization B.) Overshoot C.) Depolarization D.) Hyperpolarization
B.) Overshoot
Depolarization of excitable membranes triggers an action potential only when the membrane potential exceeds a(n) _____________ potential. A.) Action B.) Threshold
B.) Threshold
When a neuronal membrane potential changes from a positive to a negative value, the cell membrane is undergoing: A.depolarization B.repolarization C.overshoot D.none of the above
B.repolarization
The falling phase of the action potential is due primarily to: A) Na+ flow into the cell. B) Na+ flow out of the cell. C) K+ flow out of the cell. D) K+ flow into the cell E) B and D
C) K+ flow out of the cell.
Which body fluid compartment contains high levels of K+, large anions, and proteins? A) plasma B) interstitial fluid C) intracellular fluid D) A and C E) A and B
C) intracellular fluid
Which is the correctly written Nernst equation? A. log 61/z x [ion]in/[ion]out B. log 61/z x [ion]out/[ion]in C. 61/z x [ion]out/[ion]in D. 61/z x [ion]in/[ion]out
C. 61/z x [ion]out/[ion]in
A cell has a membrane potential of -100mV (more negative inside than outside) and has 1000 times more calcium ions outside the cell than inside. Which of the following describes the electrical and chemical gradients that influence the movement of calcium across the plasma membrane of this cell that is permeable to calcium? A. The chemical gradient favors and the electrical gradient opposes the entry of calcium into the cell. B. The electrical gradient favors and the chemical gradient opposes the entry of calcium into the cell. C. Both the chemical and the electrical gradients favor calcium entry into the cell. D. Both the chemical and the electrical gradients oppose calcium entry into the cell.
C. Both the chemical and the electrical gradients favor calcium entry into the cell.
Which of the following statements about the resisting membrane potential is TRUE? A. The inside of the membrane is positively charged compared to the outside. B. It is due in part to the presence of extracellular proteins C. It results, in part, from the concentration gradients for Na+ and K+ D. It is normally equal to 0 mV.
C. It results, in part, from the concentration gradients for Na+ and K+
Which of the following is FALSE about the refractory period? A. Voltage-gated Na+ channel inactivation is responsible for the absolute refractory period. B. The refractory period is important in preventing the overlap of succeeding action potentials. C. The absolute refractory period refers to that time during which a stronger stimulus will lead to the generation of a new action potential. D. The relative refractory period refers to that time during which a stronger stimulus will lead to the generation of a new action potential. E. The relative refractory period coincides with the hyperpolarization phase of the action potential.
C. The absolute refractory period refers to that time during which a stronger stimulus will lead to the generation of a new action potential.
When the membrane is at a negative potential (for e.g. at the resting membrane potential), both types of channels tend to close, whereas membrane _____________________ tends to open them. A.) polarization B.) repolarization C.) depolarization D. hyperpolarization
C.) depolarization
Which of the following statements regarding the equilibrium potential for potassium is TRUE? When the plasma membrane of a cell reaches the potassium equilibrium potential, A.all diffusion of K+ stops. B.there are equal amounts of K+ ion on both sides of the cell membrane. C.K+ outward diffusion is balanced by electrical attraction inward. D.the membrane potential is about +60 mV.
C.K+ outward diffusion is balanced by electrical attraction inward.
Solutions A and B are separated by membrane permeable to K+ but not to Cl- . Solution A is 100mM KCl and solution B is 1mM KCl. Which of the following statements about solutions A and B is TRUE? A.K+ ions will diffuse from solution A to solution B until the [K+] of both solutions is 50.5 mM. B.K+ ions will diffuse from solution B to solution A until the [K+] of both solutions is 50.5 mM. C.K+ will diffuse from solution A to solution B until a negative charge develops that opposes the movement of K+. D.KCl will diffuse from solution A to solution B until the [KCl] of both solutions is 50.5 mM
C.K+ will diffuse from solution A to solution B until a negative charge develops that opposes the movement of K+.
What part of a neuron is a region with a high density of voltage-gated sodium channels, at which action potentials initiate? A.Dendrite B.Cell body C.Trigger zone D.Axon terminal
C.Trigger zone
The active transport of a ion in or out of the cell also creates a ________________ _________________,
Concentration gradient
What does the Goldman-Hodgkin-Katz equation take into account that the Nernst equation does NOT? A. The sizes of the ions B. The solubilities of the ions C. The temperature D. The permeabilities of the ions E. The electrical charges of the ions
D. The permeabilities of the ions
Which of the following statements concerning action potential propagation velocity is CORRECT? Action potential velocity is: A. fastest in unmyelinated axons. B. unaffected if the axon becomes demyelinated, as occurs in the pathophysiological state of multiple sclerosis (MS). C. increased by myelination that increases the ability of current to leak out of the axon. D. increased by concentrating voltage-gated ion channels at specific points along the axon, called nodes of Ranvier. E. increased by insulating the entire axonal surface with myelin.
D. increased by concentrating voltage-gated ion channels at specific points along the axon, called nodes of Ranvier.
• Voltage-gated channels open or close in response to changes in membrane potential and vary by the ion they can conduct. In this class we will be discussing which ion(s) A.) Sodium B.) Potassium C.) Chlorine D.) Both A and B
D.) Both A and B
The membrane is ____________________ when the potential is more negative than the resting level. A.) Repolarization B.) Overshoot C.) Depolarization D.) Hyperpolarization
D.) Hyperpolarization
Given an extracellular Na+ concentration of 150 mM and an intracellular Na+ concentration of 15 mM, what is the equilibrium potential of a plasma membrane permeable only to Na+? (Hint - you do not need a calculator to solve this question.) A. - 61 mV B. - 30.5 mV C. 0 mV D. +30.5 mV E. + 61 mV
E. + 61 mV
Which of the following statements regarding graded potentials is FALSE? Graded potentials: A. diminish in strength over distance. B. can add up (summate) to produce greater depolarizations. C. can vary in strength and can even hyperpolarize a membrane. D. are generated in the dendrites and cell body of a neuronal cell. E. are always of equal magnitude and travel over long distances along axons.
E. are always of equal magnitude and travel over long distances along axons.
The energy used to transport a cation across the membrane has created an ______________ ___________________, that is, a difference in the net charge between two regions.
Electrical gradient
The combination of electrical and concentration gradients is called an ________________________ _________________________.
Electrochemical gradient
What are created from hollow glass tubes drawn to fine points, filled with a liquid that conducts electricity and then connected to a voltmeter, which measures the electrical difference between two points?
Electrodes
A transporter uses _____________ to move a positive ion out of the cell against its concentration gradient
Energy (ATP)
A membrane is refractory for a long time following an action potential.
False. A membrane is refractory for a brief time following an action potential.
Positive charge from the depolarized trigger zone spreads by local current flow to adjacent sections of the membrane, attracted by the Na+ that entered the cytoplasm and repelled by the negative charge of the resting membrane potential. True or False statement?
False. Positive charge from the depolarized trigger zone spreads by local current flow to adjacent sections of membrane, repelled by the Na+ that entered the cytoplasm and attracted by the negative charge of the resting membrane potential.
(Graded/Action) potentials are changes in membrane potential confined to a relatively small region of the plasma membrane.
Graded Potential
Transient changes in membrane potential that occur in neuronal dendrites or cell body. Is this a graded or action potential?
Graded Potential
Neurons signal information by ______________ potentials and ______________ potentials.
Graded potential and action potentials.
For a given concentration gradient, the greater the membrane permeability to an ion species, the (greater/lower) the contribution that ion species will make to the membrane potential.
Greater
The relative refractory period follows the absolute refractory period and is an interval during which a second action potential can be produced, but only if the stimulus strength is considerably (greater/lower) than usual.
Greater
What is the major cation found in the intracellular fluid?
K+
Graded potentials are called "graded" because the magnitude of the potential change can vary. In addition to the movement of ions on the inside and outside of the cell, charge is (lost/gained) across the membrane because the membrane is permeable to ions through open membrane channels. If additional stimuli occur before the graded potential has died away, these can be added to the depolarization from the first stimulus—a process called ______________________.
Lost, summation
At depolarizations less than the threshold (called subthreshold potentials caused by subthreshold stimuli), the positive feedback cycle cannot get started. In such cases, the membrane will return to its resting level as soon as the stimulus is removed and no action potentials are generated. Action potentials either occur _____________ or they do not occur at all, that is, action potentials occur in an all-or-none manner.
Maximally
As an action potential passes down the myelinated axon, from trigger zone to axon terminal, it passes through alternating regions of (unmyelinated/myelinated) axon and node of Ranvier.
Myelinated axons
In an actual neuron at rest, there are more open K+ channels than Na+ channels, with Cl- permeability falling in between. The resting membrane potential is not equal to the K+ equilibrium potential because a small number of _______ channels are open in the resting state—some _______ ions move into the cell canceling the effect of K+ moving out.
Na+
What are the major cations found in the extracellular fluid?
Na+ and Cl-
Most neuronal action potentials are generated by ______ and _________ channels.
Na+ and K+
Action potentials occur in non- excitable membranes (such as in neuronal and muscle cells) because these membranes contain many voltage-gated Na+ and K+ channels. Is this a true statement?
No, it is false. Action potentials occur in excitable membranes
The resting membrane potential at -70mV, is (polarized/depolarized) meaning that the outside and inside of the cell have a different net charge—changes in charge can occur in either direction from the resting membrane potential.
Polarized
Na+ channels (quickly/slowly) respond to changes in membrane voltage and open well before K+ channels during depolarization.
Quickly
Graded potentials are membrane potential changes of variable amplitude and duration that are conducted decrementally. Unlike action potentials, graded potentials have no threshold or refractory period. Is this a true statement?
True - Mocha Bear
Regardless of the size of the stimulus, if the membrane reaches threshold, the action potential generated is always the same size (action potentials are all or none). Is this a true statement?
True!
The _______________________________ measures the membrane potential when recording electrode is placed in the cell A. Voltmeter B. Recorder
Voltmeter
In an Action Potential, transient changes in membrane permeability allow Na+ and K+ to move down their electrochemical gradients. Review Slide 11 - 14 to go over Step 1 through Step 6
Wuv wuv
During the relative refractory period, some but not all of the voltage-gated Na+ channels have returned to a resting state and some of the K+ channels are still open. Can a new stimulus depolarize the membrane above the threshold?
Yes, a new stimulus can depolarize the membrane above threshold, but only if the stimulus is large or outlasts the absolute refractory period
Plasma membrane Na+/K+-ATPase pumps maintain _________ intracellular Na+ concentration and ________ intracellular K+ concentration, directly contributing a __________ component of the membrane potential.
low, high, and small
Myelinated axons limit the amount of membrane in contact with the extracellular fluid. In these axons, small sections of bare membrane—the _________ _____ _______________—alternate with longer segments wrapped in multiple layers of membrane (the myelin sheath). The myelin sheath creates a high-resistance wall that prevents ion flow out of the cytoplasm.
nodes of Ranvier
Whenever a graded potential occurs, charge flows from the place _____ ____________ ______ ____________________ __________________ __________ _________ _________________________ ______________________, which are still at the resting potential.
of origin to adjacent regions of the plasma membrane
In an actual neuron at rest, there are more open K+ channels than Na+ channels, with Cl- permeability falling in between. The resting membrane potential is largely due to the movement of K+ (out/in) of the cell down its concentration gradient through open K+ leak channels (so the inside of the cell becomes more negative than the outside).
out
An electrical gradient between the extracellular fluid and the intracellular fluid is known as the _________________ _______________ _____________ _____________ or resting membrane potential for short
resting membrane potential difference
Action potential propagation along a myelinated axon. Sodium ions entering a node reinforce the depolarization and restore the amplitude of the action potential as it passes from node to node. The apparent "jump" of the action potential as it passes from node to node is called ________________ conduction.
saltatory
The lipid barrier of the plasma membrane is a high-resistance insulator that keeps charged ions (separated/together), whereas ionic current flows readily in the aqueous intracellular and extracellular fluids.
separated
A distinguishing characteristic of action potentials is that they can travel over long distances of a meter or more without losing amplitude. That is, the action potential that reaches the end of an axon is identical to the action potential that started at the ______________ _________.
trigger zone
