Deck 45: Electrical Signals in Animals

Question 1

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

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

Answer 1

C

Question 2

Figure 45.1
Which letter in Figure 45.1 corresponds to a large efflux of K⁺ ions from the cell?

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

Answer 2

C

Question 3

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

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

Answer 3

C

Question 4

Figure 45.1
Which letter on Figure 45.1 corresponds to the action of the sodium-potassium pump and potassium leak channels?

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

Question 5

Which of the following statements about action potentials is FALSE?

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

Question 6

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 7

The Nernst equation specifies the equilibrium potential for a particular ion.This equilibrium potential is a function of

A)hydrostatic pressure.
B)ion concentration gradient.
C)osmotic gradient.
D)temperature (thermal)gradient.
E)both B and D

Question 8

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

Question 9

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

Question 10

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 11

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

A)The membrane potential would decrease.
B)The membrane potential would increase.
C)The membrane potential would be unaffected.
D)The answer depends on the thermodynamic potential.

Question 12

The axons of most neurons contain just one type of sodium channel,but several types of potassium channels.

A)true
B)false

Question 13

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

Question 14

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

A)K⁺
B)Na⁺
C)Ca⁺⁺
D)Cl⁻
E)Mg⁺⁺

Question 15

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 16

Figure 45.1
Which letter on Figure 45.1 corresponds to a large influx of Na⁺ ions into the cell?

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

Question 17

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 18

When your doctor triggers your patellar tendon reflex by tapping the front of your knee with a rubber hammer,what might she be assessing?

A)the healthy functioning of your cerebellum
B)the health of the nervous tissue between your knee and spinal cord
C)the health of the nervous tissue between your knee and your cerebral cortex
D)the health of the nervous tissue between your knee and your foot

Question 19

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 20

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

Question 21

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

Question 22

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

A)true
B)false

Question 23

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 taste
C)sense of sight
D)sense of hearing

Question 24

Neurotransmitter is released

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

Question 25

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 26

Motor neurons release the neurotransmitter acetylcholine (Ach).What would you expect to happen if the acetylcholine is released in high concentrations and is not properly degraded after it binds the receptor on the postsynaptic membrane?

A)paralysis of muscle tissue
B)gradual loss of resting potential
C)convulsions due to constant muscle stimulation
D)decrease in the frequency of action potentials
E)no effect

Question 27

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 28

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 29

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

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

Question 30

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

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

Question 31

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

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

Question 32

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 33

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

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

Question 34

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)digestive activity is stimulated
C)heartbeat is slowed
D)pupils dilate

Question 35

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

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

Question 36

The autonomic nervous system does NOT control

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

Question 37

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)communication between the hemispheres
C)transport of proteins between the hemispheres
D)source of nutrients for both hemispheres

Question 38

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

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

Question 39

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

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

Question 40

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