Action Potentials
Sample Exam Questions

Main Sample Questions List


1.    Which of the following statements concerning oligodendrocytes is FALSE?
  A. These glial cells within the central nervous system synthesize myelin, which has a relatively low protein to lipid ratio.
  B. These cells are unable to regenerate, thus accentuating conduction problems resulting from brain damage.
  C.  Each of these cells is responsible for completely myelinating a single axon.
  D. These cells wrap myelin around axons to form sheaths referred to as internodes.
  E. By producing myelin, these cells decrease the capacitance of axonal membranes.

2.    Which of the following would DECREASE the propagation velocity of an action potential down an axon?
  A. increase in distance between the axon hillock and axon terminal
  B. increase in diameter of axon
  C. increased myelination of internodes
  D. decreased myelination of internodes
  E. decrease in internal resistance of axonal cytosol to current flow

3.    Which of the following statements concerning delayed voltage-gated K+ channels is FALSE?
  A. Opening of these channels does not occur until the action potential is near its peak.
  B. Opening of these channels reduces the length of the refractory period.
  C. These channels are closed when the membrane potential returns to a value close to the K+ equilibrium potential.
  D. Without the opening of these channels, membrane repolarization would occur more slowly.
  E. These channels become fully activated when the membrane potential has shifted to -50mV.

4.    Which of the following statements concerning the voltage-gated K+ channel is FALSE?
  A. This selective channel is composed of four separate subunits, each containing six transmembrane a helices.
  B. The S4 helix of each subunit of this channel senses depolarization and causes a conformational change to open the channel pore.
  C. The nonhelical sequence of this channel between S5 and S6 dips into and lines the channel pore with hydrophilic amino acid residues.
  D. The extracellular domain of this channel functions as a "ball and chain" and is thus responsible for inactivation (closing) of the channel.
  E.  None of the above statements are false.

5.    Which of the following statements concerning a neuron is FALSE?
  A. Local potentials convey electrical signals along dendrites toward the cell body of the neuron.
  B. The axon hillock region expresses a high density of voltage-gated Na+ channels.
  C. The nodes of Ranvier have a high concentration of K+ leak channels and a low concentration of voltage-gated K+ channels.
  D. Action potentials move along the axon in the direction of the voltage-gated Na+ channels that are in the closed but activatable state.
  E. The internodes are wrapped in concentric layers of myelin.

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