Deck 5: Neuron Structure and Function

Question 1

Which of the following statements is true of graded potentials?

A)They travel over long distances.
B)They have different amplitudes.
C)They are typically found in axons.
D)They travel without decrement.

Answer 1

B

Question 2

When considering spatial summation of graded potentials,it is important to keep in mind

A)how far the potential may have traveled.
B)the initial amplitude of the potential.
C)the polarity of the potential.
D)all of the above

Answer 2

D

Question 3

What is the correct relationship between graded potentials and action potentials?

A)Graded potentials are used to generate action potentials.
B)Action potentials are used to generate graded potentials.
C)Graded potentials and action potentials are two terms for the same phenomenon.
D)All graded potentials increase the likelihood of an action potential.

Answer 3

A

Question 4

Which of the following properties of action potentials is unique to animals?

A)They are a type of electrical signal.
B)They travel at very rapid speeds.
C)They may travel via intracellular connections.
D)They allow the organism's cells to communicate with each other.

Question 5

The squid served as an ideal model system to study neurophysiology because

A)squids are invertebrates and invertebrates have a simpler nervous system than vertebrates.
B)the large diameter of the squid's neurons enabled researchers to make recordings from inside of a nerve cell.
C)fast electrical communication is a unique feature of squids.
D)squids are active predators and therefore have many nerves that can be easily studied.

Question 6

The Goldman equation can be used to determine the resting membrane potential.It accounts for all the following factors EXCEPT

A)concentration of an ion outside the cell.
B)concentration of an ion inside the cell.
C)concentration of all ion channels in the membrane.
D)permeability of the membrane for the ions.

Question 7

The relative concentrations of Na⁺ and K⁺ remain constant during a single action potential,despite movement of these ions across the membrane,because

A)they cross back immediately through recovery channels.
B)they are pumped back across using the Na⁺/K⁺ ATPase pump.
C)they are forced back across the membrane as the action potential moves away.
D)the refractory periods do not end until all ions have been returned to their original areas.

Question 8

Which of the following statements is true about voltage-gated K⁺ channels?

A)They are triggered to open at voltages near the Na⁺ equilibrium potential.
B)They are triggered to open at voltages near the resting membrane potential.
C)They are triggered to open at voltages near the threshold potential.
D)They are triggered to open at voltages below the resting membrane potential.

Question 9

Axons are found in the __________ region of a neuron.

A)signal reception
B)signal integration
C)signal conduction
D)signal transmission

Question 10

If the sodium-potassium pump was inhibited by a drug,such as digitalis,what would happen to the membrane potential of the cell?

A)The membrane potential would slowly decrease.
B)There would be an instant loss of membrane potential.
C)There would be an instant decrease followed by an increase in membrane potential.
D)The leak channels would be disrupted.

Question 11

A cell will most likely hyperpolarize when __________ enters it.

A)Cl⁻
B)Na⁺
C)Ca²⁺
D)both B and C

Question 12

Action potentials are able to travel over long distances without decaying because

A)the axons are perfectly insulated,so no current is able to leak out.
B)the action potential uses completely different ions than graded potentials.
C)once the electrical signal has passed threshold,it is impossible for the signal to decay.
D)one action potential generates the next one in an adjacent area of membrane.

Question 13

If a cell is at rest (-70 mV)and ligand-gated Na+ channels open,there will be a net movement of Na+ into the cell until

A) there are no more Na+ in the extracellular fluid.
B) the Na+ channels close.
C)the membrane potential reaches the equilibrium potential for Na+.
D)either B or C

Question 14

Which of the following conditions could allow a cell to become depolarized?

A)[X⁺]ᵢ > [X⁺]ₒ
B)change in permeability to [X⁺]
C)membrane potential = equilibrium potential
D)all of the above

Question 15

Which of the following statements is true of nerves?

A)They are composed of groups of neurons.
B)Neurons are composed of groups of nerves.
C)They act as pipes in the body,transporting fluid.
D)Signals generated in nerves can travel only short distances.

Question 16

Conduction of action potentials along an axon is termed saltatory conduction because the action potential

A)is dependent on the ions Na⁺ and K⁺,portions of salts.
B)appears to leap or jump from node to node.
C)is named after Johan Saltare,who first discovered it.
D)moves very rapidly down the axon.

Question 17

Which of the following statements correctly describes the nodes of Ranvier?

A)They are areas of myelin-covered axonal membrane.
B)They are surrounded by lipid-rich Schwann cells.
C)They are often referred to as internodes of the axons.
D)They contain a high density of voltage-gated channels.

Question 18

Movement of Na⁺ through its channels is primarily responsible for the __________ of an action potential.

A)depolarization phase
B)repolarization phase
C)hyperpolarization phase
D)after-hyperpolarization phase

Question 19

What mechanism causes the voltage-gated Na⁺ channels to close during an action potential?

A)The activation gate is voltage sensitive and closes close to the equilibrium potential for Na⁺.
B)The activation gate is sensitive to K⁺ and closes when its intracellular concentrations drop.
C)The inactivation gate has a time-dependent closure.
D)The inactivation gate is voltage sensitive and closes close to the equilibrium potential for Na⁺.

Question 20

Which of the following graded potentials will be most likely to generate an action potential?

A)a subthreshold potential
B)a suprathreshold potential
C)a hyperpolarizing potential
D)an inhibitory potential

Question 21

During the absolute refractory period,what is the state of the gates of the sodium channel?

A)Both activation and inactivation gates are closed.
B)Both activation and inactivation gates are open.
C)The activation gate is open and the inactivation gate is closed.
D)The activation gate is closed and the inactivation gate is open.

Question 22

The strongest postsynaptic signal would be achieved by which of the following combinations?

A)Low concentrations of neurotransmitter and postsynaptic receptors.
B)High concentrations of neurotransmitter and degrading enzymes.
C)Low concentrations of postsynaptic receptors and high concentrations of degrading enzymes.
D)High concentrations of neurotransmitter and low concentrations of degrading enzymes.

Question 23

All the choices below are examples of glial cells,but which one is NOT associated with the central nervous system?

A)microglia
B)astrocytes
C)schwann cells
D)oligodendrocytes

Question 24

Squid benefit from having axons of multiple sizes that innervate their muscle fibers in the mantle because

A)squid need larger diameter axons to innervate larger groups of fibers.
B)the larger diameter axons innervate fibers that are farther away because the signals are conducted more rapidly through them.
C)smaller fibers are not energetically efficient.
D)larger fibers generate larger action potentials,which allows for more neurotransmitter release.

Question 25

Increasing axon diameter decreases membrane and intracellular resistance,so it seems the two might cancel each other out in terms of their effect on the conduction speed.Yet,conduction speed is increased by increasing diameter size.Why?

A)Membrane resistance doesn't really affect conduction speed that much.
B)Intracellular resistance doesn't really affect conduction speed that much.
C)Membrane resistance decreases linearly while intracellular resistance decreases by the square of the radius.
D)Intracellular resistance decreases linearly while membrane resistance decreases by the square of the radius.

Question 26

Given the information below,the neuron with the characteristics listed in choice __________ would have the fastest conduction velocity.

A)myelinated,50 μm diameter
B)myelinated,10 μm diameter
C)unmyelinated,50 μm diameter
D)unmyelinated,10 μm diameter

Question 27

A voltage-gated K⁺ channel that is also a delayed rectifier will

A)open very quickly in response to changes in membrane potential.
B)make it very difficult to start an action potential.
C)delay the start of an action potential.
D)open slowly,increasing the length of the action potential.

Question 28

Neurons are capable of detecting and transducing incoming signals such as

A)light.
B)pressure.
C)environmental chemicals.
D)all of the above

Question 29

Myelination increases the speed of conduction by decreasing the time constant and increasing the length constant.It achieves this by

A)increasing membrane resistance and decreasing capacitance.
B)increasing both membrane resistance and capacitance.
C)decreasing membrane resistance and increasing capacitance.
D)decreasing both membrane resistance and capacitance.

Question 30

Which of the following combinations of voltage-gated channel densities would most easily allow an action potential to be generated?

A)high density of K⁺,low density of Na⁺
B)low density of K⁺,high density of Na⁺
C)high density of K⁺ and Na⁺
D)low density of K⁺ and Na⁺

Question 31

Which of the following statements is correct concerning the variation of voltage-gated ion channels?

A)Na⁺ channels have much greater diversity than K⁺ channels.
B)Typically,a more complex nervous system also contains a greater diversity of channels.
C)There is a great diversity of channels,but within a single organism,only one isoform of a channel can exist.
D)There is a large diversity of channels,but they show no physiological significance.

Question 32

A motor neuron is an example of a type of

A)afferent neuron.
B)efferent neuron.
C)interneuron.
D)sensory neuron.

Question 33

During synaptic transmission,

A)the frequency of the action potential is directly correlated with neurotransmitter release.
B)the frequency of the action potential is inversely correlated with neurotransmitter release.
C)the intracellular concentration of Ca²⁺ remains stable because of intracellular buffers.
D)the concentration of Ca²⁺ is inversely related to the amount of neurotransmitter released.

Question 34

A capacitor can store more change when it has a

A)large surface area and thick insulating layer.
B)small surface area and thin insulating layer.
C)large surface area and thin insulating layer.
D)small surface area and thick insulating layer.

Question 35

A membrane's length constant will be greatest when

A)Rm is low.
B)Rᵢ is low.
C)Rm is high.
D)both B and C

Question 36

What is the benefit of using action potentials for conductance of electrical signals,rather than simply using electrotonic spread?

A)Action potentials have a greater speed.
B)Action potentials can vary in amplitude to convey more information.
C)Action potentials can travel over longer distances.
D)both A and C

Question 37

In a neuromuscular junction,the muscle is the

A)presynaptic cell.
B)postsynaptic cell.
C)synaptic cell.
D)synapse.

Question 38

When looking at a small patch of axonal membrane,the __________ and __________ are arranged in parallel with each other,allowing current to flow through both of them if possible.

A)Rm;Rᵢ
B)Rᵢ;Cm
C)Rm;Cm
D)Cm;Rₑ

Question 39

What role does Ca²⁺ play in synaptic transmission?

A)Ca²⁺ is released into the synapse,transmitting a signal to the postsynaptic cell.
B)Ca²⁺ causes the release of vesicles from the readily releasable pool.
C)Ca²⁺ causes vesicles to move from the storage pool to docking proteins.
D)both B and C

Question 40

__________ neurons have many dendrites,but only one axon.

A)Multipolar
B)Bipolar
C)Unipolar
D)Pseudo-unipolar

Question 41

Axodendritic synapses are composed of __________ for the presynaptic cell and __________ for the postsynaptic cell.

A)axons;axons
B)dendrites;axons
C)axons;dendrites
D)axons;cell somas

Question 42

The electrical signal produced by neurons,called an __________,is capable of traveling over long distances.

Question 43

When a graded potential arrives at the axon hillock before an earlier graded potential has died out,the two potentials can be added in a process known as __________ __________.

Question 44

The synapse formed by __________ in the peripheral nervous system are similar in morphology to the __________ in the central nervous system.

A)terminal boutons;axon varicosities
B)axon varicosities;en passant synapses
C)en passant synapses;spine synapse
D)spine synapse;terminal boutons

Question 45

Oligodendrocytes and Schwann cells wrap themselves around neuronal processes,forming __________,a substance that increases conduction rates and decreases current leak.

Question 46

Vesicles found in the axon terminals that contain neurotransmitter are called __________.

Question 47

Post-tetanic potentiation at a synapse is generated by a

A)high frequency of stimulation.
B)long period of time between stimuli.
C)high frequency of stimulation followed by a short break.
D)low frequency of stimulation followed by a short break.

Question 48

Which of the following neurotransmitters is typically NOT classified as a biogenic amine?

A)acetylcholine
B)serotonin
C)epinephrine
D)dopamine

Question 49

The channels that generate an action potential are triggered to open by a change in membrane potential because they are __________ channels.

Question 50

Neurotransmitters are composed of a variety of different chemicals,including

A)amino acids.
B)neuropeptides.
C)biogenic amines.
D)all of the above

Question 51

When ligand-gated receptors open channels in dendrites,the resulting electrical signal is called a __________.

Question 52

Which of the following is a true difference between electrical and chemical synapses?

A)Electrical synapses are found in the central nervous system.
B)Electrical synapses are the most common type of synapse.
C)Electrical synapses typically send information in one direction (presynaptic cell to postsynaptic cell).
D)Electrical synapses are much faster.

Question 53

When a cell __________,the charge difference between the intracellular and extracellular fluids decreases.

Question 54

The area of the axon covered with myelin and found between the nodes of Ranvier is known as an __________.

Question 55

The action potential of Chara,an algae species,is generated by

A)Cl⁻ efflux via voltage-gated channels.
B)Cl⁻ efflux via channels opened by second messenger pathways.
C)Ca²⁺ influx via channels opened by second messenger pathways.
D)Ca²⁺ efflux via voltage-gated channels.

Question 56

A __________ transmits signals from the central nervous system to skeletal muscles.

Question 57

Neurons can produce and release different neurotransmitters.It is hypothesized that the type of neurotransmitter released is determined by

A)the amplitude of the action potential.
B)the frequency of the action potential.
C)the neurotransmitter that is available.
D)random chance.

Question 58

Metabotropic receptors typically generate a response by

A)becoming an open channel as soon as the ligand binds.
B)activating gene transcription.
C)opening an ion channel via signaling from a second messenger cascade.
D)both B and C

Question 59

__________ is a type of synaptic plasticity that results in a decrease of neurotransmitter release after repeated action potentials.

A)Synaptic facilitation
B)Post-tetanic potentiation
C)Synaptic depression
D)Presynaptic depression

Question 60

Hodgkin and Huxley,who first showed electrical current was generated by selective permeability of the membrane to ions,used the __________ as a model system.

Question 61

The membrane of an axon acts as a resistor and a __________ because it resists the flow of current and can store an electrical charge.

Question 62

__________,or afferent neurons,are capable of sending information about the environment (internal and external)to the central nervous system.

Question 63

Synapses where pre- and postsynaptic cells are directly connected so that current can pass from one cell to another are called __________.

Question 64

Briefly state the importance of voltage-gated Na⁺ channels.Explain why the tetrodotoxin (TTX)found in California newts (Taricha torosa)does not kill the newts.Would you expect garter snakes (Thamnopis sirtalis),which are predators of newts,to die once they consume the toxic newts?

Question 65

__________ receptors bind both epinephrine and norepinephrine.

Question 66

Neurotransmitter is packaged in vesicles that are released in response to an action potential.This leads to a "steplike" increase in the amount of neurotransmitter being released (one step for each vesicle),termed __________.

Question 67

The distance a membrane potential can travel before reaching 37% of its original value is termed the __________.

Question 68

A decrease in neurotransmitter release with repeated action potentials is termed _________.

Question 69

A high speed of conduction along axons is very important for the survival of organisms,particularly when quicker response times allow escape from a predator.Many factors affect speed of conduction,including temperature,myelination,and the diameter of the axon.Discuss how myelination and diameter affect the cable properties of a neuron and affect conduction speeds.

Question 70

Neurotransmitters are synthesized in the cell body,then transported in vesicles to the axon terminals using __________.

Question 71

Neurons have four functional zones,and each performs a task required for communication.What are these four zones and what structural features found in each allow it to perform its function?

Question 72

Most neurons show __________,such that one end of the neuron receives a signal and the other sends a signal.The cnidarians are an exception to this principle.

Question 73

Glial cells were originally thought to play a very minor role in the nervous system.In fact,their name is derived from the Greek word for glue.However,recent findings have demonstrated a number of functions for these cells.Discuss these functions and their importance in allowing neurons to function.

Question 74

Neurons use both graded and action potentials to carry electrical signals from one point to another.Describe the similarities and differences between these two types of signals that could be seen within an individual neuron.

Question 75

Describe the differences between electrical and chemical synapses in terms of mechanisms and functional characteristics of transmission.

Question 76

Inhibitory neurotransmitters generally cause ________________,and the changes in membrane potential are referred to as inhibitory postsynaptic potential.

Question 77

Muscarinic ACh receptors are an example of a __________ receptor,which eventually lead to the opening of an ion channel.

Question 78

The absolute and relative refractory periods of an action potential determine other parameters of action potentials such as causing unidirectional conduction and limiting their frequency.Describe what is happening during each of the refractory periods.Then use this information to describe how the different periods affect conduction and frequency.

Question 79

You have isolated two neurons,joined by a synapse,in a Petri dish.You have stimulated the first neuron at the axon hillock and successfully generated an action potential.However,there is no response by the postsynaptic neuron.Describe possible malfunctions in synaptic transmission that would prevent the postsynaptic neuron from responding as it should.

Question 80

When membrane potential changes,we use the terms depolarization,hyperpolarization,and repolarization.Explain what is happening to the membrane potential in relation to the extracellular fluid during depolarization and hyperpolarization and how each phase could be achieved by negatively charged ions.Next,explain how it is possible for the membrane to be in both hyperpolarization and repolarization at the same time.