Neurons, Synapses, and Signaling

1. Chapter 48 Neurons, Synapses, and Signaling Questions prepared by Christopher GreggLouisiana State University John LepriUniversity of North Carolina, Greensboro

2. Choose the correct pathway of information flow through neurons while taking a test, starting with reading a question and ending with marking an answer. • interneurons  motor neurons  sensory neurons  effectors • effectors  sensory neurons  interneurons  motor neurons • sensory neurons  interneurons  motor neurons  effectors • interneurons  sensory neurons  motor neurons  effectors

3. Adding a poison that specifically disables the Na+/K+ pumps to a culture of neurons will cause • the resting membrane potential to drop to 0 mV. • the inside of the neuron to become more negative relative to the outside. • the inside of the neuron to become positively charged relative to the outside. • sodium to diffuse out of the cell and potassium to diffuse into the cell.

4. For a nerve cell at its resting potential, the forces acting on potassium ions (K+) are a) none: K+ ions do not move at the resting potential. b) an electrical gradient, pulling K+ inward, and a chemical gradient, pushing K+ outward. c) an electrical gradient, pushing K+ outward, and a chemical gradient, pulling K+ inward. d) an electrical gradient, pulling K+ inward, and a chemical gradient, pushing K+ outward. e) an electrical gradient, pushing K+ outward, and a chemical gradient, pushing K+ outward.

5. A(n) ___ in Na+ permeability and/or a(n) ___ in K+ permeability across a neuron’s plasma membrane could shift membrane potential from −70 mV to −80 mV. • increase; increase • increase; decrease • decrease; increase • decrease; decrease

6. At time ZERO msec on the graph, it is likely that there was • a localized opening of K+ channels. • a localized opening of some Na+ channels. • a rapid opening of most K+ channels. • a rapid opening of most Na+ channels.

7. At step four in the graph, it is likely that • most Cl− channels closed. • most Na+ channels opened. • most K+ channels closed. • most K+ channels opened. • Na/K pumps were inactivated.

8. Of the following choices, the slowestconduction velocity for moving action potentials is likely seen in • a large-diameter, nonmyelinated axon. • a small-diameter, nonmyelinated axon. • A myelinated axon. • any of the above, as all neurons conduct action potentials at the same speed.

9. Injecting ethylene glycol tetraacetic acid (EGTA), a chelating agent that prevents calcium ions from moving across membranes, to a synaptic region would likely • increase the release of neurotransmitters by the presynaptic neuron. • decrease the release of neurotransmitters by the presynaptic neuron. • result in neurotransmitters being released, but could not bind to its receptors on the post synaptic neuron. • result in the lack of calcium ions keeping the ligand-gated ion channels open on the post synaptic neurons.

10. The use of organophosphate pesticides that inhibit acetylcholinesterase, an enzyme that breaks down acetylcholine, could cause skeletal muscle cells to • undergo more graded depolarizations, because acetylcholine would remain in the synaptic cleft longer. • undergo more graded hyperpolarizations, because acetylcholine would remain in the synaptic cleft longer. • undergo more graded depolarizations, because acetylcholine would prevent ligand-gated ion channels from opening. • undergo more graded hyperpolarizations, because excess acetylcholine opens Cl− channels.

11. Adderall, an amphetamine stimulant, works on the CNS by • increasing the release of GABA and decreasing its catabolism/reuptake. • increasing the release of serotonin and decreasing its catabolism/reuptake. • increasing the release of endorphins and decreasing their catabolism/reuptake. • increasing the release of dopamine and norepinephrine and decreasing their catabolism/reuptake.