Quiz Canvas: Chapter 2 to 5 of Purves Flashcards
Which of the following best describes nerve cells?
- Nerve cells are exceptionally good conductors of electricity (much better than copper wires).
- Nerve cells are similar in their electrical conduction properties to copper wires.
- Nerve cells are electron sinks: they absorb many electrons, but no electricity comes out of them.
- Nerve cells are unable to conduct electricity under any circumstances.
- In comparison to copper wires, nerve cells are relatively poor conductors of electricity.
In comparison to copper wires, nerve cells are relatively poor conductors of electricity.
Typically, neurons firing action potentials encode a signal’s intensity by:
- changing the frequency of their action potentials.
- All of the options
- firing at precise moments so as to signal different sized signals.
- changing the size of their action potentials
- sending signals of different sizes down different axonal branches.
changing the frequency of their action potentials.
The different electrical signals occurring in nerve cells are caused by __ the cell membrane.
- negative charges bound to the inner and outer faces of
- fluxes of ions across
- positive charges bound to the inner and outer faces of
- movements of charged proteins within the plane of
fluxes of ions across
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
- Use of active transporters to create ionic gradients
- Selective permeability of the cell membrane via different kinds of ion channels
- Consumption of metabolic energy
- Changes in membrane potential caused by the movement of ions across the cell membrane
Separation of large amounts of electrical charge, with excess positive charges stored inside the cell
Which of the following statements about the ionic permeability of cell membranes is false?
- In resting nerve cells, the membrane is quite permeable to potassium.
- The permeability of some ions can change over time.
- The permeability of some ions can be very low.
- In resting nerve cells, the membrane is quite permeable to sodium.
- All of the statements are true.
In resting nerve cells, the membrane is quite permeable to sodium.
Which of the following statements about ionic distributions in nerve cells is false?
- The total concentration of all ionic species is approximately the same for all nerve cells in all animals.
- Potassium is higher inside cells than outside cells.
- Calcium is higher outside cells than inside cells.
- Sodium is higher outside cells than inside cells
The total concentration of all ionic species is approximately the same for all nerve cells in all animals.
The proteins that establish ionic gradients are called
- voltage-gated ion channels.
- active transporters.
- passive transporters.
- ligand-gated ion channels.
- ligand-gated ion channels.
active transporters.
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.
- sodium ions can move more quickly than other ionic species.
- sodium ions are the only ions that can flow into the nerve cell body.
- the membrane potential approaches the Na+ Nernst potential during the falling phase.
- the sodium gradient explains the rising phase, falling phase, and overshoot of the action potential.
the membrane potential approaches the Na+ Nernst potential during the rising phase.
Which of the following is not integral to the action potential waveform?
- An initial decrease in the potassium current
- A “self-activating” aspect to the rise in the sodium current
- A transient increase in the sodium current
- A change in permeability of the membrane to sodium
- A change in permeability of the membrane to potassium
An initial decrease in the potassium current
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.
Sodium and potassium currents are activated in non-overlapping voltage regimes.
Voltage changes in the cell cannot be seen without voltage clamp.
Ionic conductances can be activated only in cells that have been voltage clamped.
All of the options
Voltage clamping allows simultaneous control of membrane potential and measurement of permeability changes.
Which of the following was shown to eliminate the early inward current in squid giant axons?
Removal of external potassium
Removal of external sodium
Doubling of external sodium
Removal of all external cations
Doubling of external potassium
Removal of external sodium
Which of the following does not stem from the application of Ohm’s law to ionic conductances?
The calculations stemming from Ohm’s law can be used to derive a mathematical description of the action potential.
All permeant ions experience an identical driving force at each time point during the course of an action potential.
The driving force on the ionic current is the difference between the membrane potential and the ion’s Nernst potential.
The conductance for an ion is inversely proportional to the resistance of the membrane to the passage of that ion.
The conductance for each ion can be calculated based on the measured ionic currents and the calculated driving force.
All permeant ions experience an identical driving force at each time point during the course of an action potential.
Which of the following statements on either the rising or overshoot phase of the action potential is false?
The degree of depolarization is limited in part by the activation time course of the potassium current.
The time from threshold to maximum depolarization is essentially instantaneous (i.e., too fast to be measured accurately with current electronics).
The degree of depolarization is limited in part by the declining driving force on sodium entry.
A positive feedback loop leads to a regenerative depolarization that would increase continuously if unchecked.
The degree of depolarization is limited in part by the inactivation time course for the sodium current.
The time from threshold to maximum depolarization is essentially instantaneous (i.e., too fast to be measured accurately with current electronics).
When current is injected into an axon,
the current will spread passively only if it is a depolarizing current.
the current will decay exponentially with increasing distance from the injection site (if no action potential is present).
the current will propagate as an oscillating wave independently of its polarity.
an action potential is evoked before the current has spread any distance from the point of injection.
the current will spread only in one direction.
the current will decay exponentially with increasing distance from the injection site (if no action potential is present).
Which of the following explains the unidirectional propagation of action potentials?
The polarized orientation of microtubules within the axon
The presence of a refractory period at a location where an action potential has just passed
The voltage dependence of the sodium channels
The voltage dependence of the potassium channels
Sufficient “leakiness” of the axons, such that backward propagation of action potentials is prevented
The presence of a refractory period at a location where an action potential has just passed
