37 Neurons, Synapses, and Signaling 37 Neurons, Synapses, and Signaling Questions prepared by Michael Dini, Texas Tech University

Which combination of axon features should lead an axon to communicate with downstream cells most slowly? An axon that is 1. long. 2. short. 3. wide. 4. thin. 5. myelinated. 6. nonmyelinated. 1, 3, and 5 1, 3, and 6 1, 4, and 6 2, 3, and 5 2, 4, and 6 Answer: C

Which combination of axon features should lead an axon to communicate with downstream cells most slowly? An axon that is 1. long. 2. short. 3. wide. 4. thin. 5. myelinated. 6. nonmyelinated. 1, 3, and 5 1, 3, and 6 1, 4, and 6 2, 3, and 5 2, 4, and 6 3

In a typical motor neuron, what is the correct sequence in which these structures usually become involved in transmitting an electrical current? 1. cell body 2. axon 3. axon hillock 4. dendrites 5. synaptic terminals 4, 1, 3, 2, 5 5, 4, 1, 3, 2 4, 3, 1, 2, 5 5, 4, 1, 2, 3 4, 1, 2, 3, 5 Answer: A 4

In a typical motor neuron, what is the correct sequence in which these structures usually become involved in transmitting an electrical current? 1. cell body 2. axon 3. axon hillock 4. dendrites 5. synaptic terminals 4, 1, 3, 2, 5 5, 4, 1, 3, 2 4, 3, 1, 2, 5 5, 4, 1, 2, 3 4, 1, 2, 3, 5 5

Which is not located in the CNS? Schwann cells glia interneurons oligodendrocytes spinal cord Answer: A 6

Which is not located in the CNS? Schwann cells glia interneurons oligodendrocytes spinal cord 7

Which gradient(s) is/are directly responsible for producing membrane potential? 1. concentration gradient 2. pressure gradient 3. partial pressure gradient 4. electrical gradient 1 only 1 and 4 2 and 3 1, 3, and 4 all four Answer: B 8

Which gradient(s) is/are directly responsible for producing membrane potential? 1. concentration gradient 2. pressure gradient 3. partial pressure gradient 4. electrical gradient 1 only 1 and 4 2 and 3 1, 3, and 4 all four 9

How many of these statements about hyperpolarization of a neuron is/are true? When hyperpolarization occurs, 1. membrane potential is more negative than during resting potential. 2. membrane potential is closer to EK than it is to ENa. 3. K and/or Cl channels are open. 4. if it occurs in a downstream neuron, IPSPs are more likely to be generated than are EPSPs. 5. generation of action potentials is less likely to occur. only one statement two statements three statements four statements all five statements Answer: E 10

How many of these statements about hyperpolarization of a neuron is/are true? When hyperpolarization occurs, 1. membrane potential is more negative than during resting potential. 2. membrane potential is closer to EK than it is to ENa. 3. K and/or Cl channels are open. 4. if it occurs in a downstream neuron, IPSPs are more likely to be generated than are EPSPs. 5. generation of action potentials is less likely to occur. only one statement two statements three statements four statements all five statements 11

Resting potential is mostly due to ion movements through which two of the following? 1. Na/K pumps 2. voltage-gated Na and K channels 3. ligand-gated Na and K channels 4. voltage-gated Ca2 channels 5. Na and K leak channels 1 and 2 1 and 3 1 and 5 2 and 3 4 and 5 Answer: C 12

Resting potential is mostly due to ion movements through which two of the following? 1. Na/K pumps 2. voltage-gated Na and K channels 3. ligand-gated Na and K channels 4. voltage-gated Ca2 channels 5. Na and K leak channels 1 and 2 1 and 3 1 and 5 2 and 3 4 and 5 13

What is the correct sequence in which the following events occur, leading to the cessation of acetylcholine (ACh) stimulation of downstream skeletal muscle cells? 1. migration of synaptic vesicles ceases 2. ACh release from presynaptic membrane ceases 3. hydrolysis of last ACh molecules in synaptic cleft and postsynaptic membrane 4. removal of Ca2 from synaptic terminals 5. action potentials along motor neuron cease 1, 5, 4, 2, 3 5, 1, 4, 2, 3 4, 2, 3, 5, 1 4, 1, 2, 3, 5 5, 4, 1, 2, 3 Answer: E 14

What is the correct sequence in which the following events occur, leading to the cessation of acetylcholine (ACh) stimulation of downstream skeletal muscle cells? 1. migration of synaptic vesicles ceases 2. ACh release from presynaptic membrane ceases 3. hydrolysis of last ACh molecules in synaptic cleft and postsynaptic membrane 4. removal of Ca2 from synaptic terminals 5. action potentials along motor neuron cease 1, 5, 4, 2, 3 5, 1, 4, 2, 3 4, 2, 3, 5, 1 4, 1, 2, 3, 5 5, 4, 1, 2, 3 15

It lacks an effective myelin sheath. If an axon cannot perform saltatory conduction, then what is probably true of this axon? It has fewer voltage-gated Na channels than an axon that can perform saltatory conduction. It lacks an effective myelin sheath. It is associated with either Schwann cells or oligodendrocytes. It has multiple nodes of Ranvier. It generates fewer action potentials, and requires less ATP, than an axon of equal length that can perform saltatory conduction. Answer: B 16

It lacks an effective myelin sheath. If an axon cannot perform saltatory conduction, then what is probably true of this axon? It has fewer voltage-gated Na channels than an axon that can perform saltatory conduction. It lacks an effective myelin sheath. It is associated with either Schwann cells or oligodendrocytes. It has multiple nodes of Ranvier. It generates fewer action potentials, and requires less ATP, than an axon of equal length that can perform saltatory conduction. 17

-conotoxin: blocks voltage-gated K+ channels The venom of cone snails is a cocktail of several different neurotoxins. Considering only a motor neuron, which one of these toxins should be able to cause the same ultimate effect of all of the others listed here, simply because it acts at a more upstream location, or at an earlier stage of transmission, than the others? -conotoxin: blocks voltage-gated K+ channels -conotoxin: blocks voltage-gated Ca2+ channels -conotoxin: blocks ACh receptors -conotoxin: blocks voltage-gated Na+ channels Answer: D 18

-conotoxin: blocks voltage-gated K+ channels The venom of cone snails is a cocktail of several different neurotoxins. Considering only a motor neuron, which one of these toxins should be able to cause the same ultimate effect of all of the others listed here, simply because it acts at a more upstream location, or at an earlier stage of transmission, than the others? -conotoxin: blocks voltage-gated K+ channels -conotoxin: blocks voltage-gated Ca2+ channels -conotoxin: blocks ACh receptors -conotoxin: blocks voltage-gated Na channels 19

large, proteinaceous anions Which is most directly involved in causing neurotransmitter release from the presynaptic membrane? Na K Cl Ca2 large, proteinaceous anions Answer: D 20

large, proteinaceous anions Which is most directly involved in causing neurotransmitter release from the presynaptic membrane? Na K Cl Ca2 large, proteinaceous anions 21

If a single type of neurotransmitter, released simultaneously by many different neurons onto the same downstream neuron, causes far more K channels than Na channels to open in this downstream neuron, then which of the following should occur as a result? 1. spatial summation 2. temporal summation 3. depolarization 4. hyperpolarization 5. IPSPs 6. EPSPs 1, 3, and 6 1, 4, and 5 1, 4, and 6 2, 4, and 6 2, 3, and 5 Answer: B 22

If a single type of neurotransmitter, released simultaneously by many different neurons onto the same downstream neuron, causes far more K channels than Na channels to open in this downstream neuron, then which of the following should occur as a result? 1. spatial summation 2. temporal summation 3. depolarization 4. hyperpolarization 5. IPSPs 6. EPSPs 1, 3, and 6 1, 4, and 5 1, 4, and 6 2, 4, and 6 2, 3, and 5 23