Pre-topic 4 (Ch 2 - 4)

The synaptic potential

• makes communication between nerve cells possible.

• determines the cell's resting potential.

• propagates along axons.

• results in a long-term change in a cell's membrane potential.

• occurs only in response to external stimuli.

A dull probe stimulates a Pacinian corpuscle. An electrode is placed midway down the axon, and action potentials are recorded. After one second, the probe is pushed with greater force. What change will occur in the recording?

• The threshold potential level will increase.

• The frequency of action potentials will decrease.

• The resting membrane potential will increase.

• The height of action potentials will increase.

• The frequency of action potentials will increase.

Which statement best describes the electrical properties of nerve cells?

• They are similar in their electrical conduction properties to copper wires.

• In comparison to copper wires, they are relatively poor conductors of electricity.

• They are unable to conduct electricity under any circumstances.

• They are exceptionally good conductors of electricity (much better than copper wires).

• They are electron sinks; they absorb many electrons, but no electricity comes out of them.

Which statement best describes the action potential?

• An action potential is specialized to transmit signals over only very short distances.

• An action potential occurs when the cell's membrane potential reaches threshold.

• An action potential is elicited by hyperpolarization.

• An action potential is a brief change in membrane potential from positive to negative.

• The level of depolarization is graded in proportion to the magnitude of the stimulus.

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

• Selective permeability of the cell membrane via different kinds of ion channels

• Use of active transporters to create ionic gradients

• Changes in membrane potential caused by the movement of ions across the cell membrane

• Consumption of metabolic energy

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

What is the major determinant of the permeability of a membrane to a specific ion?

• Concentration of the ion outside the cell

• Size of the ion

• Concentration of the ion inside the cell

• Number of open ion channels specific for that ion

• Electrical charge of the ion

Refer to the figure, in which the horizontal line represents a membrane that is at present impermeable to the Y⁺ ions. What would happen if the membrane became permeable to the Y⁺ ions?

• The Y⁺ ions would not move.

• The Y⁺ ions would move into the bottom chamber, down their electrical gradient.

• The Y⁺ ions would move into the top chamber, down their concentration gradient.

• The Y⁺ ions would move into the bottom chamber, down their concentration gradient.

• The Y⁺ ions would move into the top chamber, down their electrical gradient.

Which statement about electrochemical equilibrium is true?

• For a given ion concentration gradient, the resulting potential is independent of the number of charges on the ion.

• It involves the movement of a relatively large number of ions, altering the concentrations of permeant ions.

• It occurs when the potential across the membrane exactly offsets the concentration gradient.

• The size of the potential is inversely proportional to the size of the ion gradient.

• The fluxes of ion that are required to generate the membrane potential disrupt chemical electroneutrality.

Which statement best describes the Nernst equation?

• It relates the equilibrium potentials of multiple ions to their intracellular concentrations.

• It relates the equilibrium potential of an ion to its extracellular concentration.

• It relates the equilibrium potential of an ion to its intracellular concentration.

• It relates the equilibrium potential of an ion to its intra- and extracellular concentrations.

• It relates the equilibrium potentials of multiple ions to their intra- and extracellular concentrations.

Which statement regarding membrane potential and equilibrium potential is true?

• Equilibrium potential is affected by the concentration and electrical gradients of one ion; membrane potential is affected by gradients of all ions.

• Both membrane and equilibrium potentials change during an action potential.

• Membrane potential is affected by ion concentration in- and outside of the cell; equilibrium potential is affected only by ions inside the cell.

• Equilibrium potentials are the same for all neurons; membrane potentials can be different depending on the neuron.

• Equilibrium potentials are affected by membrane permeability; membrane potentials are not.