Nervous System

Which term describes the difference in electrical charge across a membrane?

• membrane potential

• resting potential

• electrical potential

• electrical current

Which term describes an electrical signal generated by neurons?

• Equilibrium potential.

• Action potential

• Membrane potential

• Resting potential

What behavior is observed if the voltage across a neuronal membrane is set to -20 mV?

• The sodium channel opens, and Na⁺ ions flow in.

• The voltage-gated sodium and potassium channels both remain closed

• The sodium channel opens, and Na⁺ ions flow out.

• The potassium channel opens, and K⁺ ions flow in.

The operation of the sodium-potassium "pump" moves

• sodium ions out of the cell and potassium ions into the cell

• sodium and potassium ions into the cell

• sodium ions into the cell and potassium ions out of the cell

• sodium and potassium ions out of the cell.

• sodium and potassium ions into the mitochondria.

The "selectivity" of a particular ion channel refers to its

• permitting passage by negative but not positive ions.

• permitting passage by positive but not negative ions

• ability to change its size depending on the ion needing transport

• binding with only one type of neurotransmitter.

• permitting passage only to a specific ion.

A "resting" motor neuron is expected to

• releases lots of acetylcholine.

• to have high permeability to sodium ions.

• to be equally permeable to sodium and potassium ions.

• have a higher concentration of sodium ions on the inside the cell than on the outside.

• exhibit a resting potential that is more negative than the "threshold" potential.

The "threshold" potential of a membrane

• is the minimum hyperpolarization needed to prevent the occurrence of action potentials.

• is the peak amount of depolarization seen in an action potential.

• is the lowest frequency of action potentials a neuron can produce.

• is the point of separation from a living from a dead neuron

• is the minimum depolarization needed to operate the voltage-gated sodium and potassium channels

Action potentials move along axons

• more rapidly in myelinated than in non-myelinated axons.

• by reversing the concentration gradients for sodium and potassium ions

• more slowly in axons of large than in small diameter

• by the direct action of acetylcholine on the axonal membrane

Which structure is not part of a neuron?

• axons

• myelin sheath

• cell body

• dendrite

Which of the following statements about action potentials in a given neuron is false?

• They occur after the threshold potential is reached

• They are identical in duration.

• They are identical in magnitude.

• They are propagated down the length of the dendrite.