Chapter 48 Mastering Biology

b. K+

13. Resting neurons are most permeable to which of the following ions? a. Na+ b. K+ c. O-- d. Cl--

d. dendrites

1. The "information receiving" section of a neuron is its _____. a. Schwann cells b. Glia c. Axon terminal d. Dendrites

a. sodium ions out of the cell and potassium ions into the cell

10. The operation of the sodium-potassium "pump" moves _____. a. sodium ions out of the cell and potassium ions into the cell b. sodium and potassium ions out of the cell c. sodium ions into the cell and potassium ions out of the cell d. sodium and potassium ions into the cell

c. hyperpolarization of the neuron

11. For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the _____. a. replacement of potassium ions with calcium ions b. depolarization of the neuron c. hyperpolarization of the neuron d. replacement of potassium ions with sodium ions

c. Membrane potential

12. Which term describes the difference in electrical charge across a membrane? a. Electrical current b. Resting potential c. Membrane potential d. Electrical potential

False

14. True or false? The potential energy of a membrane potential comes solely from the difference in electrical charge across the membrane.

a. Potassium leak channel

15. Which channel is mainly responsible for the resting potential of a neuron? a. Potassium leak channel b. Chloride leak channel c. Voltage-gated sodium channel d. Voltage-gated potassium channel

c. Action potential

16. Which term describes an electrical signal generated by neurons? a. Equilibrium potential b. Resting potential c. Action potential d. Membrane potential

b. The sodium-potassium pump moving Na+ ions out and K+ ions in

17. Which channel maintains the concentration gradients of ions across a neuronal membrane? a. The potassium leak channel allowing K+ ions out b. The sodium-potassium pump moving Na+ ions out and K+ ions in c. The sodium-potassium pump moving Na+ ions in and K+ ions out d. The sodium leak channel allowing Na+ ions out

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

18. What behavior is observed if the voltage across a neuronal membrane is set to -20 mV? a. The potassium channel opens, and K+ ions flow in. b. The sodium channel opens, and Na+ ions flow in. c. The voltage-gated sodium and potassium channels both remain closed. d. The sodium channel opens, and Na+ ions flow out.

look at image

19. Drag the labels to their appropriate locations on the diagram of the neurons below. Use only the pink labels for the pink targets (which indicate the locations of gated ion channels).

a. Cell body

2. A neuron's nucleus is located in its _____. a. Cell body b. Axon c. Myelin sheath d. Dendrite e. Synaptic terminals

look at image

20. The diagram below shows the five main transport proteins that control the distribution of Na+ and K+ ions across the plasma membrane of an axon. Assume that the membrane is at resting potential---the membrane potential of the axon remains constant at about -70 mV. Drag the arrows onto the diagram to show the direction of Na+ (gray arrows) and K+ (red arrows) movement through each transport protein at resting potential. If no ions move through a transport protein at resting potential, leave that target blank.

look at image

21. Suppose that an artificial non-gated K+ channel could be inserted into the plasma membrane of an axon at resting potential (membrane potential = -70 mV). Assume that the axon has not recently produced an action potential. What would happen when an artificial K+ channel is inserted into an axon membrane at resting potential? Answer questions 1-4 by selecting only from the three answer choices to the left of each question. Drag the correct answer to the right of each question.

look at image

22. Drag the labels onto the flowchart to show the sequence of events that occurs once the membrane potential reaches threshold. You may use a label once or not at all.

look at image

23. The fixed pattern of changes in membrane potential during an action potential is coordinated by the sequential opening and closing of voltage-gated ion channels. Can you identify the status (open/closed) of the voltage-gated Na+ and K+ channels during each phase of an action potential? Drag the appropriate labels onto the graph to indicate the status (open or closed) of the voltage-gated Na+ and K+ channels during each phase of an action potential. Labels may be used once, more than once, or not at all.

c. how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential

24. Which of the following characteristics determines when the refractory period ends? a. how long it takes for the membrane potential to return to resting potential after the undershoot phase b. how long it takes for the voltage-gated Na+ channels to close at the end of an action potential c. how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential d. how long it takes for the voltage-gated K+ channels to close during the undershoot phase e. how low the membrane potential drops below resting potential during the undershoot phase

e. After the first channel opens, the movement of many types of ions (both inside and outside the cell) alters the distribution of charges near the second channel, causing it to open.

25. Which statement correctly describes what causes the second voltage-gated Na+ channel to open? a. As Na+ ions enter the cell through the first channel, they spread out from the channel. When these Na+ ions reach the second channel, it opens. b. As Na+ ions enter the cell through the first channel, Na+ ions outside the cell move toward the open Na+ channel. c. When the concentration of Na+ ions near the second channel becomes low enough, the second channel opens. d. After the first channel opens, the movement of Na+ ions (both inside and outside the cell) alters the Na+ ion distribution across the membrane near the second channel, causing it to open. e. After the first channel opens, the movement of many types of ions (both inside and outside the cell) alters the distribution of charges near the second channel, causing it to open.

look at image

26. Match the letter of each location along the axon with the correct description of what is occurring at that position.

b,a,c

27. Enter the sequence in which the action potential would pass through the points. Enter the letters in the correct order separated by commas. For example if the order is point (c), then (b), then (a), enter c, b, a. If the action potential would not pass though a point, do not include that point in your answer.

look at image

28. Rank the axons from slowest to fastest conduction speed. If two axons have the same conduction speed, place one on top of the other.

a. a ligand-gated sodium channel

29. Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it. This is an example of _____. a. a ligand-gated sodium channel b. a chemical that inhibits action potentials c. a voltage-gated potassium channel d. a second-messenger-gated sodium channel

a. dendrites

3. A nerve impulse moves toward a neuron's cell body along _____. a. dendrites b. synaptic terminals c. oligodendrocytes d. axons e. nodes of Ranvier

look at image

30. Drag the labels onto the table to indicate which type(s) of gated ion channels are found in each membrane associated with a chemical synapse. (The letters in the table refer to the lettered structures in the image above.) Labels can be used once, more than once, or not at all.

look at image

31. Drag the labels onto the flowchart to indicate the sequence of events that occurs in the presynaptic cell (orange background) and the postsynaptic cell (blue background) after an action potential reaches a chemical synapse.

d. axon

4. A nerve impulse moves away from a neuron's cell body along _____. a. dendrites b. Nissl bodies c. synapses d. axon e. glia

c. node of Ranvier ... node of Ranvier

5. An impulse relayed along a myelinated axon "jumps" from _____ to _____. a. oligodendrocyte ... Schwann cell b. node of Ranvier ... Schwann cell c. node of Ranvier ... node of Ranvier d. Schwann cell ... Schwann cell e. Schwann cell ... node of Ranvier

c. myelin sheath

6. Axons insulated by a(n) _____ are able to conduct impulses faster than those not so insulated. a. node of Ranvier b. synaptic terminal c. myelin sheath d. layer of asbestos e. astrocytes

e. Schwann cells

7. What type of cell makes up the myelin sheath of a motor neuron? a. astrocytes b. microglial cells c. Ranvier cells d. ependymal cells e. Schwann cells

c. synaptic terminal

8. What part of a neuron relays signals from one neuron to another neuron or to an effector? a. dendrite b. axon hillock c. synaptic terminal d. axon e. node of Ranvier

a. potassium ions and proteins

9. Choose the set that includes the most charged compounds that are more abundant inside neurons, in the cytosol, than outside the neurons, in the extracellular fluid. a. potassium ions and proteins b. sodium and chloride ions c. sodium and potassium ions d. chloride ions and proteins e. proteins and sodium ions