Quiz 1 The Structure of Neurons to Action Potential

Which of the following was NOT seen in the voltage-clamp study of squid action potentials?

A sustained outward current as a result of hyperpolarization

Which of the following does NOT stem from the application of Ohm's law to ionic conductances?

All permeant ions experience an identical driving force at each time point during the course of an action potential.

Which of the following is NOT integral to the action potential waveform?

An initial decrease in the potassium current

Typically, neurons firing action potentials encode a signal's intensity by

Changing the frequency of their action potentials

Which of the following is a feature that distinguishes the four model organisms from other animals that have been intensively studied by neuroscientists?

Ease of genetic analysis and manipulation

Which technique first produced unequivocal support for the neuron doctrine of the nervous system (as opposed to the reticular theory)?

Electron microscopy of nervous tissue

The set of neurons and small ganglia associated with the digestive tract is called the

Enteric nervous system

The different electrical signals occurring in nerve cells are caused by _____ the cell membrane.

Fluxes of ions across

The scientist who shared the Nobel Prize with Camillo Golgi for his anatomical studies of the CNS was

Santiago Ramon y Cajal

Which of the following is NOT an observation that helped to identify sodium as the early current of the action potential?

When the late current was blocked, the reversal potential of the inward current shifted to a negative membrane potential.

Which of the following is NOT considered to be a "model" organism?

The marine snail Aplysia

The resting membrane potential is not exactly equal to the Nernst potential for potassium because

The membrane has some resting permeability to species other than potassium

Hodgkin and Katz proposed that sodium was the predominant ion associated with the firing of an action potential because

The membrane potential approaches the Na+ Nernst potential during the rising phase

True/False: A center-surround receptive field can be mapped by electrophysiological recording techniques.

True

True/False: A center-surround receptive field can involve an excitatory response (e.g., to touch).

True

True/False: A center-surround receptive field can involve an inhibitory response (e.g., to touch).

True

True/False: A center-surround receptive field is characterized by a circular center and a donut-shaped surround.

True

True/False: A positive feedback loop leads to a regenerative depolarization that would increase continuously if unchecked.

True

True/False: Action potential propagation requires both current flow along the axon and ion fluxes across the axon membrane.

True

True/False: Action potentials are all-or-none.

True

True/False: Action potentials boost the spatial spread of electrical signals.

True

True/False: Action potentials can propagate for long distances without decrement.

True

True/False: Action potentials can transmit signals over long distances.

True

True/False: Action potentials occur at threshold.

True

True/False: Calcium is higher outside cells than inside cells.

True

True/False: Cases of multiple sclerosis (MS) vary considerably in terms of severity and progression of the illness.

True

True/False: Chloride is higher outside cells than inside cells.

True

True/False: Electrochemical equilibrium involves the movement of a relatively small number of ions.

True

True/False: Exocytosis and endocytosis are important for synaptic communication.

True

True/False: In resting nerve cells, the membrane is quite permeable to potassium.

True

True/False: Ionic gradients are necessary for the generation of the membrane potential.

True

True/False: Magnetic resonance imaging can help diagnose some cases of multiple sclerosis (MS).

True

True/False: Mitochondria are concentrated at presynaptic terminals.

True

True/False: Most of the genes in the human genome are expressed in the CNS.

True

True/False: Multiple layers of closely opposed glial membranes wrap the axon and serve as an electrical insulator.

True

True/False: Multiple sclerosis (MS) is characterized by demyelination of axons along with some axon loss.

True

True/False: Myelin is absent at the nodes of Ranvier.

True

True/False: Myelin sheaths are created by glial cells.

True

True/False: Potassium is higher inside cells than outside cells.

True

True/False: Sodium and potassium channels are clustered at the nodes of Ranvier.

True

True/False: Sodium is higher outside cells than inside cells.

True

True/False: Symptoms of multiple sclerosis (MS) may include weakness, paralysis, double vision, monocular blindness, and abnormal somatic sensations.

True

True/False: The degree of depolarization is limited in part by the activation time course of the potassium current.

True

True/False: The degree of depolarization is limited in part by the declining driving force on sodium entry.

True

True/False: The degree of depolarization is limited in part by the inactivation time course for the sodium current.

True

True/False: The direction of the ion gradient determines the polarity of the membrane potential.

True

True/False: The permeability of some ions can be very low.

True

True/False: The permeability of some ions can change over time.

True

True/False: The size of the potential is proportional to the size of the ion gradient.

True

True/False: The spread of a passive signal is limited by the leakage of current out of the axon.

True

True/False: The time course of passive signal spread slows with increasing leakiness of the axon.

True

A measured membrane potential of +58 mV would be consistent with _____ inside the cell and _____ outside the cell.

10 mM Na+, 100 mM Na+

Neurons exhibit a threshold above which an action potential is triggered because of

A positive feedback loop between depolarization and sodium current activation

Which of the following is NOT a cause of sensory receptor potentials?

Brain waves

The brain imaging technique that makes use of a narrow X-ray beam is called

CT

Studies of the ionic basis of the action potential in squid giant axon found that

Decreasing sodium outside the cell decreases the size of the action potential

Voltage clamp data, in which investigators analyzed membrane conductances during action potentials, showed all of the following EXCEPT

Depolarization leads to a time-dependent inactivation of the potassium current

The transmembrane potential is generated by

Diffusion of ions down a concentration gradient

True/False: A center-surround receptive field is found only in primary sensory cortex.

False

True/False: Action potentials are elicited by hyperpolarization.

False

True/False: Every gene in the human genome is expressed in the CNS.

False

True/False: For a given ion concentration gradient, the resulting potential is independent of the number of charges on the ion.

False

True/False: Glial cells rapidly transmit long-range electrical signals.

False

True/False: Humans have 100 times more genes than invertebrate animals such as Drosophila.

False

True/False: Humans have three to four times more genes than mice have.

False

True/False: In resting nerve cells, the membrane is quite permeable to sodium.

False

True/False: It was recently proven that all cases of multiple sclerosis (MS) are due to persistent infection by a tropical parasite.

False

True/False: Myelin serves to sharply increase the time constant of the axon.

False

True/False: The endoplasmic reticulum is concentrated in axons.

False

True/False: The membrane length constant describes how far an action potential can propagate along an axon.

False

True/False: The time from threshold to maximum depolarization is essentially instantaneous (i.e., too fast to be measured accurately with current electronics).

False

True/False: The total concentration of all ionic species is approximately the same for all nerve cells in all animals.

False

True/False: There are tens of thousands of neuron-specific genes (i.e., genes that are not expressed outside the CNS).

False

Which of the following is NOT a reason for the usefulness of the squid giant axon in neuronal studies?

Giant ion channels allow for the insertion of recording electrodes into the channels.

The equation used to calculate membrane potential when there are multiple permeant ions is called the

Goldman equation

Which of the following best describes nerve cells?

In comparison to copper wires, nerve cells are relatively poor conductors of electricity.

In their studies of the resting membrane potential of the squid giant axon, Hodgkin and Katz found that

Increasing potassium outside the axon depolarized the axon's potential

Which of the following is NOT an established role for glial cells?

Integrating information to assist neural computation

The inventor of voltage clamp was

Kenneth Cole

The structural brain imaging technique that relies on atoms behaving as small magnets is called

MRI

The synaptic potential

Makes communication between nerve cells possible

Cognitive neuroscience is concerned with

Mathematical ability, emotions, language, and abstract thought

The type of nerve cell that synapses upon muscles is called a(n)

Motor neuron (or motoneuron)

Action potentials are generated

Only when the cell reaches threshold

The mode of action potential propagation along myelinated axons is called

Salutatory

The _____ most directly affects the rate of information processing within the central nervous system.

Propagation speed of action potentials

Which of the following is NOT a usual kind of potential exhibited by nerve cells?

Reaction

Which of the following was shown to eliminate the early inward current in squid giant axons?

Removal of external sodium

A neuron that innervates (i.e., makes synaptic contact with) a large number of other neurons

Represents divergent neural signaling

Which of the following type of glial cell myelinates peripheral axons?

Schwann cells

Which of the following is NOT necessary for neurons to communicate electrically?

Separation of large amounts of electrical charge, with excess positive charges stored inside the cell

Which of the following is NOT part of the brain?

Spinal cord

The technique that first revealed the tremendous diversity of neuronal cell types (numbering in the hundreds or thousands in vertebrate animals) is called

The Golgi stain

Which of the following factors is important in determining the membrane potential when there are multiple permeant ions?

The concentration gradient of the individual ionic species and the permeability of the membrane to the individual ionic species

When current is injected into an axon,

The current will decay exponentially with increasing distance from the injection site (if no action potential is present)

In an experiment using a series of voltage steps to study the two different ionic currents associated with the action potential, it was found that

The early current increased initially, but then it decreased in size as the voltage step was increased

Which of the following explains the unidirectional propagation of action potentials?

The presence of a refractory period at a location where an action potential has just passed

Which of the following was NOT one of the features of Hodgkin and Huxley's mathematical model?

The undershoot can be accounted for by the time course of sodium current reactivation.

Representation of which of the following is best accomplished using a topographic map?

The visual world

Which of the following is an advantage that intracellular recordings have over extracellular recordings?

They can record synaptic and receptor potentials.

Antibody staining is used to

Visualize the distribution of specific proteins in the nervous system

For which of the following reasons was the development of the voltage clamp critical to investigations of the ionic basis of the action potential?

Voltage clamping allows simultaneous control of membrane potential and measurement of permeability changes.