Deck 48: Electrical Signals in Animals

Question 1

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates the falling phase of the action potential?

A) I
B) II
C) III
D) IV

Answer 1

C

Question 2

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates the minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels?

A) I
B) II
C) IV
D) V

Answer 2

A

Question 3

What type of neurons is responsible for the interpretation of sensory input?

A) sensory neurons
B) motor neurons
C) interneurons
D) peripheral neurons

Answer 3

C

Question 4

What do we call a membrane potential in which there is no net movement of an ion across a membrane?

A) a graded potential
B) a threshold potential
C) an equilibrium potential
D) an action potential

Question 5

A nerve is a collection of ________.

A) dendrites
B) nerve cell bodies
C) synapses
D) axons

Question 6

Which of these ions is more abundant in the interior of a resting neuron than in the fluid surrounding the neuron?

A) Cl-
B) Ca++
C) Na+
D) K+

Question 7

A researcher uses the chemical inhibitor cyanide to reduce ATP production in a neuron. What would be one effect of preventing ATP production?

A) The sodium and potassium channels would all be closed.
B) The membrane would become more permeable to sodium.
C) The "resting" distribution of potassium and sodium ions would be altered.
D) The physical structure of the plasma membrane would break down.

Question 8

Which of the following describes the ion channels of a resting neuron?

A) The channels are always open, but the concentration gradients of ions frequently change.
B) The channels are always closed, but ions move closer to the channels during excitation.
C) The channels are open or closed depending on their type, and are specific as to which ion can traverse them.
D) The channels are open in response to stimuli, and then they close simultaneously.

Question 9

If you treat a neuron with a drug that increases membrane permeability to Na+, how would you expect the equilibrium potential for Na+ to change?

A) increase
B) decrease
C) repolarize
D) remain unchanged

Question 10

Which of the following best explains the observation that a resting neuron membrane, while highly permeable to potassium ions, is not at the equilibrium potential for potassium?

A) The membrane is also slightly permeable to sodium ions.
B) The membrane is also fully permeable to calcium ions.
C) The membrane is also impermeable to sodium ions.
D) The membrane is also highly permeable to chloride ions.

Question 11

Which of the following is expected in a neuron that is receiving input through tens of thousands of synapses?

A) highly branched dendrites
B) highly branched axons
C) a highly branched cell body
D) thousands of axons

Question 12

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 become more negative.
B) The membrane potential would become less negative.
C) The membrane potential would be unaffected.
D) The membrane potential would become positive.

Question 13

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

A) hydrostatic pressure
B) the ion concentration gradient
C) the osmotic gradient
D) the temperature (thermal) gradient

Question 14

In a chemical synapse, where would we find an ionotropic receptor?

A) the presynaptic cell
B) the postsynaptic cell
C) axon hillocks
D) cell bodies

Question 15

In which of the following locations would we expect to find the release of neurotransmitter molecules?

A) inside of an axon hillock
B) along the length of a dendrite
C) in a chemical synapse
D) in the cell body of a neuron

Question 16

The concentrations of sodium and potassium ions are very different inside and outside a neuron. What contributes to these differences?

A) osmosis
B) diffusion of chloride ions
C) sodium-potassium pumps
D) exocytosis and endocytosis

Question 17

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates the point when the membrane potential is closest to the equilibrium potential for potassium?

A) I
B) II
C) III
D) IV

Question 18

The activity of the sodium-potassium pump results in the movement of which ions across the plasma membrane?

A) It pumps sodium and potassium ions into the cell.
B) It pumps sodium and potassium ions out of the cell.
C) It pumps sodium ions into the cell and potassium ions out of the cell.
D) It pumps sodium ions out of the cell and potassium ions into the cell.

Question 19

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates the point when the membrane's permeability to sodium ions is greatest?

A) I
B) II
C) IV
D) V

Question 20

You feel something touch your arm, think it might be a fly, and you extend your arm to scare it away. In which order is the information about the touch processed?

A) integration, sensory input, motor output
B) motor output, integration, sensory input
C) sensory input, motor output, integration
D) sensory input, integration, and motor output

Question 21

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates when the neuronal membrane is at its resting potential?

A) I
B) II
C) IV
D) V

Question 22

Which of the following would most likely occur if you experimentally depolarize the middle of an axon to threshold using an electronic probe?

A) no action potential will be initiated
B) an action potential will be initiated and proceed only in the normal direction toward the axon terminal
C) an action potential will be initiated and proceed only back toward the axon hillock
D) two action potentials will be initiated and will proceed in opposite directions

Question 23

Which of the following would produce the fastest possible conduction velocity of action potentials?

A) thin, unmyelinated axons
B) thin, myelinated axons
C) thick, unmyelinated axons
D) thick, myelinated axons

Question 24

Which of the following will induce a graded hyperpolarization of a membrane under normal resting conditions?

A) increasing its permeability to Na+
B) decreasing its permeability to Cl-
C) increasing its permeability to Ca++
D) increasing its permeability to K+

Question 25

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.
D) The membrane potential would first become more negative and then less negative.

Question 26

Why are action potentials conducted usually in one direction along an axon?

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

Question 27

For a neuron with an initial membrane potential at -70 mV, what would be the result of an increase in the movement of potassium ions out of that neuron's cytoplasm?

A) depolarization of the neuron
B) hyperpolarization of the neuron
C) replacement of potassium ions with sodium ions
D) replacement of potassium ions with calcium ions

Question 28

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 shift of resting potential
C) slow decrease of resting potential and action potential amplitudes
D) No effect; the substances counteract each other.

Question 29

Which of the following statements about action potentials is correct?

A) Action potentials for a given neuron vary in magnitude.
B) Action potentials for a given neuron vary in duration.
C) Action potentials propagate towards the synaptic terminal of an axon.
D) Movement of ions during the action potential occurs mostly through the sodium pump.

Question 30

After the depolarization phase of an action potential, the resting potential is restored by ________.

A) voltage-gated potassium channels opening and sodium channels inactivating
B) a decrease in the membrane's permeability to potassium and chloride ions
C) a brief inhibition of the sodium-potassium pump
D) the opening of more voltage-gated sodium channels

Question 31

Conduction and refractory periods are typical of ________.

A) action potentials
B) graded hyperpolarizations
C) excitatory postsynaptic potentials
D) threshold potentials

Question 32

Pyrethroid insecticides prevent the voltage-gated sodium channels of insects from inactivating. Neurons that were exposed to pyrethroids would ________.

A) become hyperpolarized during an action potential
B) not repolarize during an action potential
C) not be able to open potassium channels
D) not release neurotransmitter molecules

Question 33

What is the best indicator of the strength of a signal in a neuron?

A) the rate at which action potentials are produced
B) the type of neurotransmitter involved in the signal
C) the types of ions involved in conveying the action potential
D) the degree of depolarization and repolarization of the membrane

Question 34

Which of the following describes the cause of the undershoot phase of hyperpolarization?

A) the slow opening of voltage-gated sodium channels
B) the sustained opening of voltage-gated potassium channels
C) the rapid opening of voltage-gated calcium channels
D) the slow restorative actions of the sodium-potassium ATPase

Question 35

Which answer explains why Na+ ions enter the cell when voltage-gated Na+ channels are opened in neurons?

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

Question 36

A neurophysiologist is investigating 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 a likely explanation?

A) The fish's axons are smaller in diameter than the axons in the crab.
B) The fish's axons are myelinated. The crab's axons are not myelinated.
C) The fish's axons are not myelinated. The crab's axons are myelinated.
D) There is a higher percentage of ion channels in the axons of the crab compared with the percentage of ion channels in fish axons.

Question 37

At a neuromuscular junction, what process releases acetylcholine into the synaptic cleft?

A) osmosis
B) active transport
C) diffusion
D) exocytosis

Question 38

Action potentials move along axons ________.

A) more slowly in axons of large diameter than in axons of small diameter
B) by activating the sodium-potassium "pump" at each point along the axonal membrane
C) more rapidly in myelinated than in unmyelinated axons
D) by reversing the concentration gradients for sodium and potassium ions

Question 39

If a pebble is tossed into a pond, it generates small ripples that decrease in size as the ripples move away from the point where the pebble struck the water. The decreasing size of the ripples as they move away from the initial splash is most like the way that signals spread ________.

A) in a graded potential
B) in an action potential
C) during hyperpolarization
D) during depolarization

Question 40

In multiple sclerosis, the myelin sheaths around the axons of the brain and spinal cord are damaged and demyelination results. How does multiple sclerosis manifest at the level of the action potential?

A) Action potentials move in the opposite direction on the axon.
B) Action potentials move more slowly along the axon.
C) No action potentials are transmitted.
D) Action potentials grow stronger as they move down an axon.

Question 41

What chemical affects neuronal function but is not stored in presynaptic vesicles?

A) acetylcholine
B) epinephrine
C) nitric oxide
D) GABA

Question 42

The botulinum toxin, which causes botulism, inhibits ________.

A) presynaptic release of acetylcholine
B) absorption of acetylcholine
C) binding of acetylcholine on the postsynaptic membrane
D) synthesis of acetylcholine receptors

Question 43

Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of ________.

A) a voltage-gated channel
B) a ligand-gated channel
C) a second-messenger-gated channel
D) a chemical that inhibits action potentials

Question 44

The following are events in the transmission of a signal at a chemical synapse.
1) Neurotransmitter binds with receptors associated with the postsynaptic membrane.
2) Calcium ions rush into neuron's cytoplasm.
3) An action potential depolarizes the membrane of the presynaptic axon terminal.
4) The ligand-gated ion channels open.
5) The synaptic vesicles release neurotransmitter into the synaptic cleft.
Which sequence of events is correct?

A) 1 → 2 → 3 → 4 → 5
B) 2 → 3 → 5 → 4 → 1
C) 3 → 2 → 5 → 1 → 4
D) 4 → 3 → 1 → 2 → 5

Question 45

Which of the following is an amino acid that functions as a neurotransmitter at most inhibitory synapses in the brain?

A) acetylcholine
B) endorphin
C) nitric oxide
D) GABA

Question 46

Which of the following is an example of a ligand-gated channel?

A) electrical synapses in a vertebrate heart
B) acetylcholine receptors at a neuromuscular junction
C) the breakdown of acetylcholine in a neuromuscular synapse
D) the action of NO on smooth muscle

Question 47

Which of the following will decrease the heart rate of a vertebrate?

A) acetylcholine
B) endorphin
C) nitric oxide
D) GABA

Question 48

Where are neurotransmitters released in a synapse?

A) the presynaptic membrane
B) axon hillocks
C) cell bodies
D) the smooth endoplasmic reticulum

Question 49

What happens when a resting neuron's membrane depolarizes?

A) There is a net diffusion of Na+ out of the cell.
B) The equilibrium potential for K+(Ek) becomes more positive.
C) The neuron's membrane voltage becomes more positive.
D) The cell's inside becomes more negative than the outside.

Question 50

Which of the following is the most likely effect of applying the naturally occurring acetylcholinesterase inhibitor onchidal (produced by the mollusc Onchidella binneyi) to a neuromuscular junction?

A) the muscle cell would not be able to contract
B) the muscle cell would receive constant stimulation
C) there would be a decrease in the frequency of action potentials
D) there would be no effect on the muscle cell function

Question 51

What part of a neuron functions as the integrating center, where the membrane potential reflects the summed effect of all EPSPs and IPSPs?

A) the nuclear membrane
B) region of the cell body where dendrites converge
C) the presynaptic terminals of the longest axon
D) the axon hillock

Question 52

Where are neurotransmitter receptors located?

A) the nuclear membrane
B) the nodes of Ranvier
C) the postsynaptic membrane
D) synaptic vesicle membranes

Question 53

Excitatory postsynaptic potentials (EPSPs) occurring at multiple synapses on the same postsynaptic neuron can add together through ________.

A) temporal summation
B) spatial summation
C) highly branched dendrites
D) the generation of substance P

Question 54

A common feature of action potentials is that they ________.

A) cause the membrane to hyperpolarize and then depolarize
B) can undergo temporal and spatial summation
C) are triggered by a depolarization that reaches threshold
D) move at the same speed along all axons

Question 55

Neurotransmitters categorized as inhibitory are expected to ________.

A) activate G proteins
B) close potassium channels
C) open sodium channels
D) hyperpolarize the membrane

Question 56

Which of the following is a characteristic of an electrical synapse?

A) gap junctions
B) acetylcholine
C) G protein-coupled receptors
D) summation

Question 57

What would most likely happen if twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive in close proximity at a postsynaptic neuron?

A) a stronger action potential
B) a weaker action potential
C) no action potential
D) many action potentials

Question 58

Which of the following explains why one-way synaptic transmission occurs?

A) Only dendrites can respond to electrical signals.
B) The postsynaptic cell contains most of the synaptic vesicles.
C) Receptors for neurotransmitters are mostly found on the postsynaptic membrane.
D) Myelination prevents two-way transmission of signals.

Question 59

Why are action potentials usually conducted in one direction?

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

Question 60

An inhibitory postsynaptic potential (IPSP) will occur if a membrane is made more permeable to ________.

A) potassium ions
B) sodium ions
C) ATP
D) all neurotransmitter molecules

Question 61

Which of the following is the most direct result of depolarizing the presynaptic membrane of an axon terminal?

A) Voltage-gated calcium channels in the membrane open.
B) Synaptic vesicles fuse with the membrane.
C) Ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft.
D) An EPSP or IPSP is generated in the postsynaptic cell.

Question 62

Suppose a particular neurotransmitter causes an IPSP in postsynaptic cell X and an EPSP in postsynaptic cell Y. A likely explanation is that ________.

A) the threshold value in the postsynaptic membrane for cell X is different from that for cell Y
B) the axon of cell X is myelinated, but that of cell Y is not
C) only cell Y produces an enzyme that terminates the activity of the neurotransmitter
D) cells X and Y express different receptor molecules for this particular neurotransmitter