Deck 43: Animal Nervous Systems

Question 1

If the activity of the sodium-potassium pump was completely stopped, what would happen to the neuron's membrane potential?

A) no effect
B) slow rise in membrane potential
C) immediate loss of action potentials
D) immediate loss of resting potential

Answer 1

B

Question 2

Why are action potentials usually conducted in one direction?

A) The axon hillock has a higher membrane potential than the terminals of the axon.
B) Voltage- gated channels for both Na+ and K+ open in only one direction.
C) The brief refractory period prevents reopening of voltage- gated Na+ channels.
D) Ions can flow along the axon in only one direction.
E) The nodes of Ranvier conduct potentials in one direction.

Answer 2

C

Question 3

Which of the following types of ions are most likely to cross the plasma membrane of a resting neuron?

A) Na⁺
B) Mg⁺⁺
C) Cl^-
D) Ca⁺⁺
E) K⁺

Answer 3

K⁺

Question 4

Figure 43.1
Which letter on Figure 43.1 corresponds to a large influx of Na⁺ ions into the cell?

A) A
B) B
C) C
D) D
E) E

Question 5

If the sodium- potassium pump were inactivated by a drug, what would happen to the neuron's membrane potential?

A) slow decrease of resting potential
B) immediate loss of resting potential
C) immediate loss of action potentials
D) no effect

Question 6

The depolarization phase of an action potential requires

A) opening of K⁺ channels in the membrane.
B) opening of Na⁺ channels in the membrane.
C) a K⁺ concentration gradient across the membrane.
D) a Na⁺ concentration gradient across the membrane.
E) both B and D

Question 7

Tetrodotoxin blocks voltage- gated sodium channels and ouabain blocks sodium- potassium pumps. If you added both tetrodotoxin and ouabain to a solution containing neural tissue, what responses would you expect?

A) no effect; the substances counteract each other
B) slow decrease of resting potential and action potential amplitudes
C) immediate loss of action potential with gradual loss of resting potential
D) immediate loss of resting potential

Question 8

Figure 43.1

-How do myelin sheaths increase the speed with which action potentials are propagated along an axon?

A) They increase the permeability of Na⁺ ions in the plasma membrane.
B) They cause action potentials to "jump" down the axon rather than travel in a continuous path along every site on the axon.
C) They amplify the action potential by increasing sodium influx along the entire distance of the neuron.
D) All of the above answers apply.

Question 9

Figure 43.1
Which letter on Figure 43.1 corresponds to the action of the sodium- potassium pump and potassium leak channels?

A) A
B) B
C) C
D) D
E) E

Question 10

Which of the following statements about action potentials is FALSE?

A) Movement of ions during the action potential occurs mostly through the sodium pump.
B) The frequency of action potentials, not their size, is the meaningful signal.
C) Action potentials are propagated down the length of the axon.
D) All action potentials for a given neuron are identical in magnitude.
E) All action potentials for a given neuron are identical in duration.

Question 11

Figure 43.1
Which letter in Figure 43.1 corresponds to a large efflux of K⁺ ions from the cell?

A) A
B) B
C) C
D) D
E) E

Question 12

The squid giant axon is approximately 500 µm in diameter compared to 2µm for a typical human axon). Due to the size of the axon,

A) it can transmit action potentials much faster than small axons can.
B) it can transmit action potentials at a higher frequency i.e., fire faster) than small axons can.
C) It can generate larger amplitude action potentials than small axons can.
D) It can generate longer duration action potentials than small axons can.
E) Answers A and C are both correct.

Question 13

The concentrations of ions are very different inside and outside a nerve cell due to

A) sodium- potassium pumps.
B) osmosis.
C) diffusion.
D) symports and antiports.

Question 14

What would be a consequence of a person having Na⁺ levels in the blood and interstitial fluids that are well below normal?

A) Neurons would not be able to undergo normal action potentials.
B) Action potentials would occur with greater frequency.
C) Neurons would all be depolarized.
D) Neurons would remain refractory following closure of voltage- gated sodium channels.
E) K⁺ channels would open to compensate for changes in membrane potential.

Question 15

Why do Na⁺ ions enter the cell when voltage- gated Na⁺ channels are opened in neurons?

A) because the Na⁺ concentration is much higher outside the cell than it is inside
B) because the Na⁺ ions are attracted to the negatively charged interior
C) because the Na⁺ ions are actively transported by the sodium- potassium pump into the cell
D) both A and B
E) both A and C

Question 16

What type of neuron can exist entirely within the central nervous system CNS)?

A) interneuron
B) motor neuron
C) sensory neuron
D) A and B
E) all of the above

Question 17

If you experimentally increase the concentration of K⁺ inside a cell, while maintaining other ion concentrations as they were, what would happen to the cell's membrane potential?

A) The membrane potential would become more negative.
B) The membrane potential would remain the same.
C) The membrane potential would become less negative.

Question 18

A neurophysiologist is investigating nerve reflexes in two different animals-a crab and a fish. Action potentials are found to pass more rapidly along the fish's neurons. What is the most likely explanation?

A) The fish's axons are smaller in diameter; small axons transmit action potentials faster than large axons do.
B) Unlike the crab, the fish's axons are wrapped in myelin.
C) There are more ion channels in the axons of the crab compared with fish axons.
D) Answers A and B are both correct.

Question 19

What would probably happen if a long neuron had one continuous myelin sheath down the length of the axon with no nodes of Ranvier?

A) The signal would fade because it is not renewed by the opening of more sodium channels.
B) There could be no action potential generated at the axon hillock.
C) The action potential would be propagated nearly instantaneously to the synapse.
D) None of the above could happen.

Question 20

A toxin that binds specifically to voltage- gated sodium channels in axons would be expected to

A) prevent the hyperpolarization phase of the action potential.
B) prevent the depolarization phase of the action potential.
C) increase the release of neurotransmitter molecules.
D) have most of its effects on the dendritic region of a neuron.
E) prevent graded potentials.

Question 21

You are walking your dog at night in the forest. Your dog barks at a strange noise and you are startled. Which of the following physiological responses are most likely to occur?

A) the gallbladder is stimulated to release bile
B) pupils dilate
C) heartbeat is slowed
D) digestive activity is stimulated

Question 22

If twice as many inhibitory postsynaptic potentials IPSPs) as excitatory postsynaptic potentials EPSPs) arrive at a postsynaptic neuron in close proximity, is the integration of signals by the postsynaptic neuron likely to produce an action potential?

A) yes
B) no

Question 23

The corpus callosum is a network of axons that connects the two hemispheres of the cerebrum. What do you hypothesize the primary function of the corpus callosum is?

A) structural support for both hemispheres
B) transport of proteins between the hemispheres
C) source of nutrients for both hemispheres
D) communication between the hemispheres

Question 24

A large meal is likely to result in activity in which set of nerves?

A) parasympathetic nerves
B) somatic nerves
C) sympathetic nerves
D) both B and C

Question 25

If a disease or disorder interferes with learning and memory, which of the following should the mechanism of the disease should involve?

A) changes to the chemical structure of neurotransmitters
B) molecular and structural changes at synapses
C) changes in myelination of axons
D) structural changes to ion channels in axon
E) changes in the concentration of ions in the extracellular fluid surrounding neurons

Question 26

If an action potential is triggered in a neuron, what must have happened?

A) membrane potential was reached
B) threshold potential was reached
C) resting potential was reached

Question 27

Neurotransmitter is released

A) when enough voltage- gated sodium channels open.
B) when threshold potential is reached.
C) in response to an action potential depolarizing the presynaptic membrane.

Question 28

The autonomic nervous system does NOT control

A) stomach activity.
B) pupil dilation and constriction.
C) airway diameter.
D) heart rate.
E) contraction of skeletal muscle.

Question 29

How could you increase the magnitude of inhibitory postsynaptic potentials IPSPs) generated at a synapse?

A) Increase K⁺ permeability.
B) Increase the influx of calcium.
C) Increase sodium- potassium pump activity.
D) All of the above apply.

Question 30

Which of the following manipulations would reduce the release of neurotransmitter from a presynaptic neuron terminal?

A) addition of tetrodotoxin to the extracellular fluid at the axon terminal
B) increase in extracellular sodium and potassium ion concentrations at the axon terminal
C) reduction in extracellular calcium ion concentration at the axon terminal
D) All of the above manipulations would reduce the release of neurotransmitter.

Question 31

Most synapses found so far in the mammalian central nervous system CNS) are classified as chemical rather than electrical.

Question 32

Upon witnessing a robber hold up a convenience store at gunpoint, which of the following reactions would your nervous system initiate?

A) increased heartbeat
B) constriction of airways
C) dilation of pupils
D) all of the above
E) only A and C

Question 33

Where are the sodium channels that trigger an action potential located?

A) axon dendrite
B) axon hillock
C) axon terminal
D) axon cell body

Question 34

Stem cell transplants may someday be used to treat Parkinson's disease. Researchers are hopeful that these cells would alleviate the symptoms of Parkinson's disease by

A) replenishing missing ion channels.
B) preventing temporal lobe seizures.
C) repairing sites of traumatic brain injury.
D) secreting the neurotransmitter dopamine.
E) both A and D.

Question 35

Which nervous pathway does sensory information travel through to elicit a response in the effector cells?

A) PNS efferent division CNS interneuron PNS afferent division effector
B) CNS efferent division CNS interneuron PNS afferent division effector
C) CNS afferent division CNS interneuron PNS efferent division effector
D) PNS afferent division CNS interneuron PNS efferent division effector

Question 36

Functional studies of the human brain have involved

A) lesion studies of individuals with damage to particular brain regions.
B) direct electrical stimulation of regions of cerebral cortex.
C) recording from single neurons during memory tasks.
D) both A and B.
E) all of the above.

Question 37

Neurotransmitters can be either excitatory or inhibitory. Which of the following neurotransmitters usually have an inhibitory effect on the post- synaptic cell?

A) gamma- aminobutyric acid
B) dopamine
C) acetylcholine
D) glutamate

Question 38

Action potentials are normally generated at the axon hillock and propagated down the axon away from the cell body. If you experimentally depolarized an axon to the threshold level at a point halfway down the axon, what would happen?

A) An action potential would be generated that would travel to the synapse with the next neuron.
B) An action potential would be generated that would travel back towards the cell body.
C) No action potential could be generated at this location.
D) Answers A and B both apply.

Question 39

If a person were to have a stroke in the occipital lobe of the cerebrum, which of the following functions would
Most likely be affected?

A) sense of touch
B) sense of hearing
C) sense of taste
D) sense of sight

Question 40

Neurotransmitters categorized as inhibitory are expected to

A) close potassium channels.
B) close chloride channels.
C) act independently of their receptor proteins.
D) open sodium channels.
E) hyperpolarize the membrane.