An inhibitory postsynaptic potential:
A. is produced by simultaneous increases in permeability to both Na+ and K+.
B. occurs when a ligand-gated ion channel increases its permeability to K+.
C. is a small depolarization in a postsynaptic cell.
D. can be summed with other IPSPs to trigger an action potential in the postsynaptic cell.
E. is produced by an increase in permeability to only Na+.
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Question 2) The main role of calcium ions at chemical synapses is to
A. depolarize the axon terminal of the presynaptic cell.
B. bind to neurotransmitter receptors on the postsynaptic cell.
C. cause fusion of synaptic vesicles with the plasma membrane of the axon terminal.
D. interfere with IPSPs in the postsynaptic cell.
E. diffuse across the synaptic space and enter the postsynaptic cell.
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Question 3) At an excitatory chemical synapse between two neurons,
A. there is increased permeability of the postsynaptic cell to both Na+ and K+.
B. a small hyperpolarization of the postsynaptic membrane occurs when the synapse is activated.
C. an action potential in the presynaptic neuron always causes an action potential in the postsynaptic neuron.
D. excitation occurs because K+ enters the postsynaptic cell.
E. action potentials spread through gap junctions between cells.
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Question 4) Exocytosis of neurotransmitter into the synaptic cleft is triggered by an influx of ______ in response to the arrival of an action potential in the axon terminal.
A. K+
B. Na+
C. Ca2+
D. ATP
E. Cl-
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Question 5) The regions of axon membrane that lie between regions of myelin are the
A. ganglia.
B. nodes of Ranvier.
C. synaptic membranes.
D. glial cells.
E. pia mater.
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Question 6) An action potential does not re-stimulate the adjacent membrane that was previously depolarized because
A. stimulation is inhibited by the myelin sheath.
B. it is impossible for an action potential to be propagated along an axon toward the nerve cell body.
C. the resting membrane potential of the axon is too positive.
D. the resting membrane potential of the axon is too negative.
E. that area of the membrane is in the absolutely refractory period.
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Question 7) How is the strength of a stimulus encoded by neurons?
A. by the size of action potentials
B. by the frequency of action potentials
C. by the duration of action potentials
D. by whether the action potential peak is positive or negative
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Question 8) Which of the following statements concerning the rate of action potential propagation is TRUE?
A. It is faster in small-diameter axons than in large-diameter axons.
B. It is faster for a strong stimulus than for a weak one.
C. It is faster in myelinated axons than in nonmyelinated axons.
D. It is faster in the dendrites than in the axon.
E. It occurs at the same rate in all axons, regardless of their diameter.
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Question 9) The relative refractory period of an axon coincides with the period of
A. activation and inactivation of voltage-dependent Na+ channels.
B. Na+ permeability that is greater than that during the depolarization phase.
C. increased K+ flux into the cell.
D. increased K+ permeability of the cell.
E. Increased Na+ flux through K+ channels.
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Question 10) Which of the following statements concerning the properties of action potentials is TRUE?
A. The rate of propagation of an action potential down an axon is independent of stimulus strength.
B. Action potentials can undergo summation.
C. A supra-threshold stimulus can stimulate an action potential during the absolute refractory period.
D. Action potentials generally propagate from the axon terminal toward the initial segment.
E. Increasing the size of a stimulus will increase the amplitude of an action potential.
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