Deck 43: Animal Nervous Systems

Question 1

Hyperpolarization of a membrane can be induced by ________.

A) increasing its membrane's permeability to Na+
B) decreasing its membrane's permeability to H+
C) decreasing its membrane's permeability to Cl−
D) increasing its membrane's permeability to Ca++
E) increasing its membrane's permeability to K+

Answer 1

E

Question 2

ATP hydrolysis directly powers the movement of ________.

A) K+ out of cells
B) Na+ out of cells
C) Na+ into cells
D) Ca2+ into cells
E) Cl− into cells

Answer 2

B

Question 3

Refer to the following graph of an action potential to answer the question(s) below.
The cell is not hyperpolarized; however, repolarization is in progress, as the sodium channels are closing or closed, and many potassium channels have opened at label ________.

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

Answer 3

C

Question 4

The point of connection between two communicating neurons is called the ________.

A) axon hillock
B) dendrite
C) synapse
D) cell body
E) glia

Question 5

Refer to the following graph of an action potential to answer the question(s) below.
The neuronal membrane is at its resting potential at label ________.

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

Question 6

The membrane potential in which there is no net movement of the ion across the membrane is called the ________.

A) graded potential
B) threshold potential
C) equilibrium potential
D) action potential
E) inhibitory postsynaptic potential

Question 7

Refer to the following graph of an action potential to answer the question(s) below.
The minimum depolarization needed to operate the voltage-gated sodium and potassium channels is indicated by the label ________.

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

Question 8

The operation of the sodium-potassium "pump" moves ________.

A) sodium 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 ions out of the cell and potassium ions into the cell
E) sodium and potassium ions into the mitochondria

Question 9

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels ________.

A) are always open, but the concentration gradients of ions frequently change
B) are always closed, but ions move closer to the channels during excitation
C) open and close depending on stimuli and are specific as to which ion can traverse them
D) open and close depending on chemical messengers and are nonspecific as to which ion can traverse them
E) open in response to stimuli and then close simultaneously, in unison

Question 10

Although the membrane of a "resting" neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also ________.

A) fully permeable to sodium ions
B) slightly permeable to sodium ions
C) fully permeable to calcium ions
D) impermeable to sodium ions
E) highly permeable to chloride ions

Question 11

Refer to the following graph of an action potential to answer the question(s) below.
The membrane's permeability to sodium ions is at its maximum at label ________.

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

Question 12

Most of the neurons in the human brain are ________.

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

Question 13

Refer to the following graph of an action potential to answer the question(s) below.
The membrane potential is hyperpolarized at label ________.

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

Question 14

In a resting potential, an example of a cation that is more abundant as a solute inside a neuron than it is in the interstitial fluid outside the neuron is ________.

A) HCO3−
B) Cl−
C) Ca++
D) Na+
E) K+

Question 15

Opening all of the sodium channels of a neuron at rest should move its membrane potential to ________.

A) −90 mV
B) −70 mV
C) 0 mV
D) +10 mV
E) +40 mV

Question 16

The "selectivity" of a particular ion channel refers to its ________.

A) permitting passage by positive but not negative ions
B) permitting passage by negative but not positive ions
C) ability to change its size depending on the ion needing transport
D) binding with only one type of neurotransmitter
E) permitting passage only to a specific ion

Question 17

For a neuron at rest with a membrane potential of −65 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the ________.

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
E) neuron switching on its sodium-potassium pump to restore the initial conditions

Question 18

The nucleus and most of the organelles in a neuron are located in the ________.

A) dendritic region
B) axon hillock
C) axon
D) cell body
E) axon terminals

Question 19

What type of neuron exists entirely within the central nervous system (CNS)?

A) interneuron
B) motor neuron
C) sensory neuron
D) interneuron and motor neuron
E) interneuron, sensory neuron, and motor neuron

Question 20

A basic nervous system ________.

A) must include chemical senses, mechanoreception, and vision
B) includes a minimum of 12 effector neurons
C) has information flow in only one direction: toward an integrating center
D) has information flow in only one direction: away from an integrating center
E) includes sensory information, an integrating center, and effectors

Question 21

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 the threshold potential
D) move at the same speed along all axons
E) require the diffusion of Na+ and K+ through ligand-gated channels to propagate

Question 22

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 first become more negative then rebound to be positive.
D) The membrane potential would remain the same.

Question 23

The fastest possible conduction velocity of action potentials is observed in ________.

A) small diameter, non-myelinated neurons
B) small diameter, myelinated neurons
C) large diameter, non-myelinated neurons
D) large diameter, myelinated neurons

Question 24

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

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

Question 25

Action potentials move along axons ________.

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

Question 26

Action potentials are normally carried in only one direction: from the axon hillock toward the axon terminals. If you experimentally depolarize the middle of the axon to threshold, using an electronic probe, then ________.

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, one going toward the axon terminal and one going back toward the hillock
E) an action potential will be initiated, but it will die out before it reaches the axon terminal

Question 27

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

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

Question 28

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 all be depolarized.
B) Neurons would not be able to undergo normal action potentials.
C) Action potentials would occur with greater frequency.
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 29

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

A) K+
B) Na+
C) Ca2+
D) Cl−
E) Mg2+

Question 30

Self-propagation and refractory periods (or refractory states) are typical of ________.

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

Question 31

Why are action potentials usually conducted in one direction?

A) The nodes of Ranvier conduct potentials in 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) Ions can flow along the axon in only one direction.
E) Voltage-gated channels for both Na+ and K+ open in only one direction.

Question 32

Immediately after an action potential passes along an axon, it is not possible to generate a second action potential. Thus, we state that the membrane is briefly ________.

A) hyperexcitable
B) refractory
C) fully depolarized
D) above threshold
E) at the equilibrium potential

Question 33

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 are propagated down the length of the axon.
D) Movement of ions during the action potential occurs mostly through the sodium pump.

Question 34

The "threshold" potential of a membrane is the ________.

A) point of separation from a living to a dead neuron
B) lowest frequency of action potentials a neuron can produce
C) minimum hyperpolarization needed to prevent the occurrence of action potentials
D) minimum depolarization needed to operate the voltage-gated sodium and potassium channels
E) peak amount of depolarization seen in an action potential

Question 35

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 neuron is less likely to generate an action potential.
E) The cell's inside is more negative than the outside.

Question 36

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) opening of Ca2+ channels in the membrane
D) a K+ concentration gradient across the membrane
E) a Ca2+ concentration gradient across the membrane

Question 37

In the sequence of permeability changes for a complete action potential, the first of these events that occurs is the ________.

A) activation of the sodium-potassium pump
B) inhibition of the sodium-potassium pump
C) opening of voltage-gated sodium channels
D) closing of voltage-gated potassium channels
E) opening of voltage-gated potassium channels

Question 38

The "undershoot" phase of after-hyperpolarization is due to ________.

A) slow opening of voltage-gated sodium channels
B) sustained opening of voltage-gated potassium channels
C) rapid opening of voltage-gated calcium channels
D) slow restorative actions of the sodium-potassium ATPase
E) ions that move away from their open ion channels

Question 39

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) prevent graded potentials
D) increase the release of neurotransmitter molecules
E) have most of its effects on the dendritic region of a neuron

Question 40

The organization of the nervous system with a large ganglion or brain at the anterior end of the organism is termed ________.

A) integration
B) a nerve net
C) cephalization
D) refraction
E) bilateral symmetry

Question 41

In a simple synapse, neurotransmitter chemicals are released by ________.

A) the dendritic membrane
B) the presynaptic membrane
C) axon hillocks
D) cell bodies
E) ducts on the smooth endoplasmic reticulum

Question 42

Which of the following will increase the speed of an action potential moving down an axon?
I) Action potentials move faster in larger-diameter axons.
II) Action potentials move faster in axons lacking potassium ion channels.
III) Action potentials move faster in myelinated axons.

A) only I and II
B) only II and III
C) only I and III
D) I, II, and III

Question 43

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; myelination increases the speed of action potential transmission.
C) There are more ion channels in the axons of the crab compared with fish axons.
D) Unlike the crab, the fish's axons are wrapped in myelin, and the fish's axons are smaller in diameter; small axons transmit action potentials faster than large axons do.

Question 44

In a simple synapse, neurotransmitter chemicals are received by ________.

A) the postsynaptic membrane
B) the presynaptic membrane
C) axon hillocks
D) cell bodies
E) ducts on the smooth endoplasmic reticulum

Question 45

Neural transmission across a mammalian synapse is accomplished by ________.

A) the movement of sodium and potassium ions from the presynaptic neuron into the postsynaptic neuron
B) impulses traveling as electrical currents across the synapse
C) impulses causing the release of a chemical signal and its diffusion across the synapse
D) impulses ricocheting back and forth across the synapse
E) the movement of calcium ions from the presynaptic into the postsynaptic neuron

Question 46

Which letter in the accompanying figure corresponds to a large influx of Na+ ions into the cell?

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

Question 47

Neurotransmitters are released from axon terminals via ________.

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

Question 48

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 insulate the axon, preventing K+ ions from exiting the neuron.
D) They cause action potentials to "jump" down the axon rather than travel in a continuous path along every site on the axon.

Question 49

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

Question 50

The release of acetylcholine from the terminal of a motor neuron is most directly linked to the ________.

A) entry of potassium into the axon terminal
B) exit of potassium from the axon terminal
C) entry of sodium into the axon terminal
D) exit of sodium from the axon terminal
E) entry of calcium into the axon terminal

Question 51

The activity of acetylcholine in a synapse is terminated by its ________.

A) active transport across the presynaptic membrane
B) diffusion across the presynaptic membrane
C) active transport across the postsynaptic membrane
D) diffusion across the postsynaptic membrane
E) degradation on the postsynaptic membrane

Question 52

The following steps refer to various stages in transmission at a chemical synapse.
1) Neurotransmitter binds with receptors associated with the postsynaptic membrane.
2) Calcium ions rush into the 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 a supply of 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
E) 5 → 1 → 2 → 4 → 3

Question 53

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

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

Question 54

The surface on a neuron that discharges the contents of synaptic vesicles is the ________.

A) dendrite
B) axon hillock
C) node of Ranvier
D) postsynaptic membrane
E) presynaptic membrane

Question 55

In multiple sclerosis the myelin sheaths around the axons of the brain and spinal cord are damaged and demyelination results. How does this disease manifest at the level of the action potential?
I) Action potentials move in the opposite direction on the axon.
II) Action potentials move more slowly along the axon.
III) No action potentials are transmitted.

A) only I
B) only II
C) only III
D) only II and III
E) only I and II

Question 56

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 57

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

A) because the Na+ concentration is much lower 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) because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ ions are attracted to the negatively charged interior
E) because 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 58

Which letter in the accompanying figure corresponds to closed voltage-gated sodium channels and closed voltage-gated potassium channels?

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

Question 59

An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to ________.

A) K+
B) Na+
C) Ca2+
D) ATP
E) acetylcholine

Question 60

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) The action potential would be propagated normally to the synapse.

Question 61

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 listed responses are correct.

Question 62

Which of the following manipulations would reduce the release of neurotransmitter from a presynaptic neuron terminal?
I) reduction in extracellular calcium ion concentration at the axon terminal
II) increase in extracellular sodium ion concentrations at the axon terminal
III) addition of tetrodotoxin to the extracellular fluid at the axon terminal

A) only I
B) only II
C) only III
D) only II and III
E) only I and II

Question 63

Neurotransmitters can affect postsynaptic cells by ________.
I) initiating signal transduction pathways in the cells
II) causing molecular changes in the cells
III) affecting ion-channel proteins
IV) altering the permeability of the cells

A) I and III
B) II and IV
C) II and III
D) III and IV
E) I, II, III, and IV

Question 64

An example of ligand-gated ion channels is ________.

A) the spreading of action potentials in the heart
B) acetylcholine receptors at the neuromuscular junction
C) K+ leakage channels
D) action potentials on the axon
E) second-messenger systems that activate postsynaptic neurons

Question 65

Which neurotransmitter excites muscle cells?

A) acetylcholine
B) epinephrine
C) endorphin
D) nitric oxide
E) gamma-aminobutyric acid (GABA)

Question 66

Neurotransmitters categorized as inhibitory are expected to ________.

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

Question 67

An important excitatory neurotransmitter in the central nervous system (CNS) is ________.

A) acetylcholine
B) epinephrine
C) glutamate
D) nitric oxide
E) gamma-aminobutyric acid (GABA)

Question 68

Receptors for neurotransmitters are of primary functional importance in assuring one-way synaptic transmission because they are mostly found on the ________.

A) axonal membrane
B) axon hillock
C) postsynaptic membrane
D) mitochondrial membrane
E) presynaptic membrane

Question 69

What happens if the correct ligand binds to ligand-gated sodium channel in a post-synaptic neuron?

A) An excitatory post-synaptic potential occurs.
B) A second-messenger ion channel opens.
C) A signal crosses an electrical synapses.
D) An inhibitory post-synaptic potential occurs,

Question 70

In a synapse, what initiates the release of neurotransmitter?

A) when an action potential depolarizes the presynaptic membrane
B) when threshold potential is reached
C) when enough voltage-gated sodium channels open to release calcium into the synapse
D) the presence of gap junctions joining the synaptic membranes

Question 71

Excitatory postsynaptic potentials (EPSPs) produced nearly simultaneously by different synapses on the same postsynaptic neuron can also add together, creating ________.

A) summation
B) interference
C) only action potentials
D) the refractory state

Question 72

Muscle cells are stimulated by neurotransmitters released from the synaptic terminals of ________.

A) T tubules
B) motor neuron axons
C) sensory neuron axons
D) motor neuron dendrites
E) sensory neuron dendrites

Question 73

Functionally, which cellular location is the neuron's "decision-making site" as to whether or not an action potential will be initiated?

A) axonal membranes
B) axon hillock
C) presynaptic membranes
D) mitochondrial membranes

Question 74

Which of the following is a 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) The postsynaptic cell produces an action potential.
D) Ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft.
E) An excitatory postsynaptic potential (EPSP) or inhibitory postsynaptic potential (IPSP) is generated in the postsynaptic cell.

Question 75

Which neurotransmitter is involved in reducing perceptions of pain?

A) acetylcholine
B) endorphin
C) epinephrine
D) nitric oxide
E) gamma-aminobutyric acid (GABA)

Question 76

When two excitatory postsynaptic potentials (EPSPs) occur at a single synapse so rapidly in succession that the postsynaptic neuron's membrane potential has not returned to the resting potential before the second EPSP arrives, the EPSPs add together, producing ________.

A) summation
B) inhibition
C) tetanus
D) the refractory state
E) an action potential with an abnormally high peak of depolarization

Question 77

What is the space between the presynaptic and postsynaptic membranes?

A) the axon hillock
B) the nodes of Ranvier
C) the synaptic cleft
D) synaptic vesicle membranes
E) the myelin sheath

Question 78

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

A) A stronger action potential results.
B) A weaker action potential results.
C) No action potential results.
D) A normal action potential results.

Question 79

The botulinum toxin, which causes botulism, reduces the synaptic release of ________.

A) acetylcholine
B) epinephrine
C) endorphin
D) nitric oxide
E) gamma-aminobutyric acid (GABA)

Question 80

An important inhibitory neurotransmitter of the human brain is ________.

A) acetylcholine
B) dopamine
C) glutamate
D) nitric oxide
E) gamma-aminobutyric acid (GABA)