Chapter 7: Nerve Cells & Electrical Signalling Flashcards
Which of the following correctly lists the components of the central nervous system?
brain and spinal cord
Which of the following is located in the autonomic nervous system?
both sympathetic and parasympathetic nervous systems
Which of the following accurately describes afferent neurons?
They transmit information from the periphery to the CNS.
What is the functional unit of the nervous system?
neurons
On what portion of the neuron do action potentials propagate?
axon
Information is transmitted from cell to cell across the chemical synapse via a(n) ________.
neurotransmitter
An action potential originates at the ________ and travels along the axon until it reaches the ________.
axon hillock : axon terminal
What type of ion channels in the membrane of neurons allow ions to move across the membrane at rest and thereby contribute to resting membrane potential?
leak channels
What type of ion channels in the membrane of neurons open or close in response to a neurotransmitter binding to its receptor?
ligand-gated channels
In a neuron, where is the greatest concentration of voltage-gated sodium and voltage-gated potassium channels?
axon hillock
In a neuron, where are voltage-gated calcium channels located?
axon terminal
What is the structural classification of a neuron composed of a single axon and a number of dendritic projections from the nerve cell body?
multipolar
Which of the following is a functional classification of neurons that, for the most part, are bipolar in structure and carry information from the peripheral axon to the central axon?
afferent neurons
Which of the following terms is NOT used to describe a bundle of axons in the central or peripheral nervous system?
ganglia
Which of the following cells is NOT classified as a glial cell?
ventricular cell
What type of cell enhances the velocity of electrical transmission of an action potential along an axon in the central nervous system?
oligodendrocyte
Which of the following best describes the function of the myelin sheath?
reduce a membraneʹs ion permeability
Which of the following is the correct term for the movement of an electrical charge across a membrane?
current
Which of the following determines the resistance to an ionʹs movement across a membrane?
ion channels within the membrane
What is the inverse of resistance?
conductance
Which of the following is NOT a factor involved in the determination of resting membrane potential?
concentration of sodium receptors
Which of the following statements about sodium is FALSE?
At the potassium equilibrium potential, there is an electrical force driving sodium ions out of the cell.
Which of the following best describes the electrochemical forces acting on sodium and potassium ions at the resting membrane potential?
The force on sodium ions is to move into the cell, and the force on potassium ions is to move out of the cell.
Given a cation with an equilibrium potential of -55 mV, if the plasma membrane of the cell is permeable only to this ion, then which of the following best describes the resting membrane potential?
-55 mV
At the resting membrane potential, the membrane is most permeable to ________, which moves ________ the cell due to its electrochemical gradient.
potassium : out of
At the resting membrane potential, the electrochemical gradient for sodium across the membrane is such that the net flux for sodium movement is directed ________, thereby causing the cellʹs membrane potential to become more ________.
inward : positive
The membrane potential at which there is no net flux of an ion across the membrane is called that ionʹs ________.
equilibrium potential
The presence of the ________ prevents the dissipation of the concentration gradient for Na +.
Na+/K+ pump
The Na+/K+ pump is called an electrogenic pump because the imbalance between ________.
Na+ out to K+ in leaves the inside of the cell with a net negative charge
Why is the electrical potential of a membrane at rest closest to potassiumʹs equilibrium potential than to sodiumʹs equilibrium potential?
more potassium channels are open, allowing more potassium to move out of the cell
If, under resting conditions, the membrane is much more permeable to sodium than potassium, what would happen to the resting membrane potential?
approach sodiumʹs equilibrium potential
As a membraneʹs permeability to a particular ion increases, membrane potential will move ________ that ionʹs ________.
closer to : equilibrium potential
What equation is used to calculate the membrane potential based on ion concentration gradients and permeabilities?
GHK equation
Membrane permeability is altered in the short term (milliseconds to seconds) by changes in the ________ of ion channels.
gating
The opening of an ion channel increases a cell membraneʹs ________, whereas ________ will decrease.
conductance : resistance
The fact that a cell has an electrical potential difference across its membrane makes that cell ________.
polarized
A change in a cellʹs membrane potential, such that it becomes more positive, is referred to as a ________.
depolarization
A change in a cellʹs membrane potential, such that it becomes more negative, is referred to as a ________.
hyperpolarization
A ________ is a subthreshold change in membrane potential within the cell body that decays as it travels away from its point of origin.
graded potential
The direction of change in membrane potential, in response to a stimulus that initiates a graded potential, is dependent upon ________.
the ion channels that are opened or closed
Which of the following does NOT produce graded potentials?
arrival of a suprathreshold stimulus at the axon hillock
Which of the following statements is FALSE? (graded potentials)
Graded potentials and action potentials are all-or-none.
The ________ in graded potential that occurs as current spreads along the membrane happens as a consequence of the ________ of current across the membrane.
decrement : leakage
Which of the following is an example of spatial summation?
Two stimuli from two sources produce graded potentials on the same neuron at the same
time such that the two potentials sum.
Which of the following changes in membrane potential is considered excitatory?
depolarization only
The spread of voltage by passive charge movement is called ________.
electrotonic conduction
If the graded potential remains above threshold once it reaches the ________, an action potential will be generated.
axon hillock
Which of the following characteristics does NOT describe an action potential?
rapid increase in potassium permeability
The opening of sodium channels causes a rapid ________ of sodium that ________ the neuronʹs membrane.
influx : depolarizes
The depolarization phase of the action potential is generated by a rapid ________.
opening of sodium channels
The repolarization phase of the action potential in a neuron is driven by the ________.
closure of sodium channels and opening of potassium channels
The patterns of change in ion channel permeability that occur during an action potential are due to ________ gating of voltage-sensitive potassium and sodium channels.
time-dependent
For the sodium channel to open and allow sodium into the cell, ________.
the activation and inactivation gates must both be open
Which of the structures below lacks voltage-gated ion channels responsible for the production of action potentials?
epithelial cell membrane
Which of the following events is fastest?
opening sodium activation gates
Stimuli A and B are both suprathreshold stimuli that last for one second, but stimulus A is stronger. Which of the following statements is TRUE?
Stimulus A will cause a higher frequency of action potentials.
The repolarization phase of action potentials in neurons is due primarily to ________.
potassium flow out of the cell
During which of the following states are the majority of voltage-gated sodium channels closed and incapable of opening?
during the absolute refractory period
The regenerative nature of a sodium channelʹs activation gate refers to the situation where an activation gate opens causing a depolarization that triggers which of the following?
opening of other sodium channelsʹ activation gates
The stimulation of an inadequate number of sodium channels for the generation of a positive sodium channel feedback loop is considered a ________ stimulus.
subthreshold
In order to generate an action potential, the magnitude of the inward sodium current must be large enough to overcome which of the following?
outward potassium current
What terminates the positive feedback loop that is involved in the generation of an action potential?
closure of inactivation gates on sodium channels
Why will the magnitude of an action potential never reach sodiumʹs equilibrium potential?
the inward movement of sodium is countered by the outward movement of potassium
The all-or-none principle, associated with the action potential, states that ________.
once membrane potential reaches threshold, an action potential will be generated and
that action potential will always be the same magnitude
In order for a neuron to move from the absolute to the relative refractory period, a majority of that neuronʹs sodium channels must have their ________.
inactivation gates open
Toward the end of the relative refractory period, the continued decrease in stimulus intensity required to initiate an action potential is caused by ________.
decreased potassium permeability
The stimulus intensity required to initiate an action potential is ________ through the course of the relative refractory period.
progressively reduced
Which of the following characteristics of an action potential does NOT result directly from the refractory period?
the peak level of depolarization reached
The time between action potentials is directly determined by the ________ the graded potential at the axon hillock.
amplitude of
For an unmyelinated axon, conduction velocity is primarily determined by the ________.
diameter of the axon
As an action potential is propagated away from the axon hillock, why does propagation continue in one direction?
the region just behind the action potential is in the absolute refractory period
In myelinated nerve fibers, where do action potentials occur?
nodes of Ranvier
The jumping of an action potential from node-to-node is called ________.
saltatory conduction
Which of the following axons would have the fastest conduction velocity?
diameter = 20 microns, myelinated
What percentage of people with diabetes develop peripheral neuropathy?
30
What percentage of people with neuropathy have it secondary to diabetes?
30
Why do the distributions of sodium and potassium ions across the plasma membrane of neurons not change appreciably, even following hundreds of action potentials?
The movement of sodium and potassium ions that occurs during an action potential is
countered by the active transport of these ions by the Na+/K+ pump.
Effector organs act as receptors that detect information about the external environment and transmit that information to the central nervous system.
FALSE
Excitable cells are capable of producing action potentials.
TRUE
Axons can branch.
TRUE
Leak channels are most concentrated in the soma of neurons.
FALSE
Afferent neurons are generally bipolar neurons.
TRUE
Oligodendrocytes are located in the peripheral nervous system, providing the myelin sheath that forms the nodes of Ranvier.
FALSE
Schwann cells are the only glial cells in the peripheral nervous system.
TRUE
The number of ions whose movement across the membrane creates the resting membrane potential are so few that their movement does not affect that ionʹs concentration gradient.
TRUE
The membrane potential of a cell is determined exclusively by that cellʹs sodium and potassium permeability.
FALSE
At the resting membrane potential, a cell is at equilibrium.
FALSE
The Na+/K+ pump is electrogenic.
TRUE
An ionʹs net electrochemical force will tend to move that ion across the membrane in a direction that will cause membrane potential to move toward that ionʹs equilibrium potential.
TRUE
The Nernst equation is used to calculate the resting membrane potential.
FALSE
The GHK equation is used to calculate the equilibrium potential for a specific ion.
FALSE
In temporal summation, stimuli from different sources are applied at the same time such that they overlap and sum.
FALSE
Excitatory graded potentials are those where the stimulus initiates a hyperpolarization of the cell.
FALSE
Under resting conditions, the sodium channel responsible for generating an action potential is closed and incapable of opening.
FALSE
Both activation and inactivation gates of a sodium channel are stimulated at the same time by a depolarization with the inactivation gate acting more slowly than the activation gate, thereby allowing sodium to enter the cell.
TRUE
The magnitude of the action potential is dependent upon the extent to which the change in membrane potential is above threshold.
FALSE
During the relative refractory period, the stimulus intensity required to initiate an action potential is elevated.
TRUE
Once an action potential is generated, it will always depolarize the neighboring membrane above threshold, ensuring the action potential will travel along the axon without interruption.
TRUE
Tingling can be a sign of diabetic neuropathy.
TRUE
Diabetic neuropathy can affect nerves of the autonomic nervous system.
TRUE
autonomic nervous system
The portion of the efferent branch of the nervous system that communicates to glands and cardiac muscle.
efferent nervous system
The portion of the peripheral nervous system that communicates to effector organs.
somatic nervous system
Portion of the efferent nervous system that communicates with skeletal muscle.
afferent nervous system
The portion of the peripheral nervous system that transmits information from sensory receptors to the central nervous system.
central nervous system
The brain and spinal cord.
peripheral nervous system
Provides communication between peripheral organs and the brain and spinal cord.
enteric nervous system
Nervous system of the intestinal tract.
Information gathered about our internal environment (i.e., fullness of the stomach, blood pressure, etc.) is called ________ information.
visceral
What is the most common neuronal cell type?
interneuron
What is the only glial cell found outside of the central nervous system?
Schwann cell
Each ________ provides the myelin sheath for many axons in the central nervous system.
oligodendrocyte
Once a membrane potential has been developed, the force that drives a particular ion across the membrane is its ________.
electrochemical gradient
When they are not at equilbrium, an ion will move across the membrane in a direction that moves membrane potential toward that ionʹs ________.
equilibrium potential
What is the passive spread of current along a membrane called?
electrotonic conduction
Following the opening of the activation gate of the sodium channel, the ________ gate closes shortly thereafter.
inactivation
The inactivation gate is opened by ________
repolarization of the membrane to resting membrane potential
The fact that the opening of some sodium channels can induce several other sodium channels to open describes the ________ property of these channels.
regenerative
What is the level of membrane depolarization required to induce the sodium channelʹs positive feedback loop called?
threshold
The type of ion channels located along the axon is (ligand-gated channels / voltage-gated channels).
voltage-gated channels
In the peripheral nervous system, myelin is formed by ________. In the central nervous system, myelin is formed by ________. Gaps in the myelin are called ________. Propagation of action potentials in myelinated axons is called ________.
Schwann cells : oligodendrocytes : nodes of Ranvier : saltatory conduction
At rest, the plasma membrane is more permeable to (sodium / potassium).
potassium
The resting membrane potential is close to the (sodium / potassium) equilibrium potential.
potassium
Which is larger, an action potential or a graded potential? Which lasts longer, an action potential or a graded potential?
action potential : graded potential
During the rapid depolarization phase of an action potential, the plasma membrane is more permeable to (sodium / potassium).
sodium
The sodium inactivation gate (opens / closes) with depolarization.
closes
Increased permeability to what ion is responsible for the relative refractory period?
potassium
As the membrane potential moves further away from the equilibrium potential for a certain ion, the electrochemical force acting on that ion (increases / decreases).
increases
At the peak of an action potential, the electrochemical force is greater for (sodium / potassium).
potassium
The current produced by a specific ion moving across the plasma membrane increases as conductance (increases / decreases).
increases
