Deck 18: Mechanisms of Extrasynaptic Communication

Question 1

The three regions into which neurotransmitters are released extrasynaptically are the neuropil, the CSF, and the

A) blood stream.
B) cytoplasm.
C) synaptic cleft.
D) choroid plexus.
E) vesicles.

Answer 1

A

Question 2

One result of the volume transmission method of extrasynaptic communication is that

A) extrasynaptic communication happens more quickly than synaptic communication.
B) the effects occur after a time-lag based on the distance to the receptors.
C) neurotransmitter reuptake is more efficient than in synaptic communication.
D) neurotransmitters are not packaged in vesicles prior to release.
E) extrasynaptic communication produces fast negative feedback.

Answer 2

B

Question 3

A fundamental role of glial cells in extrasynaptic communication is to

A) help transport dense-core vesicles from release sites to receptor sites.
B) put the 'brakes' on signaling by absorbing signaling molecules.
C) pass along messages by capturing and releasing signaling molecules.
D) help form electrical connections between one neuron and the next.
E) promote negative feedback by inhibiting neurons that release neurotransmitters.

Answer 3

C

Question 4

In extrasynaptic communication, glial cells

A) are the only cells capable of extrasynaptic neurotransmitter release.
B) work in coordination with neurons, with both capable of extrasynaptic neurotransmitter release.
C) provide the physical scaffolding needed for molecules to pass from one neuron to the next.
D) help construct a filter to prevent extrasynaptically released molecules from leaving the brain.
E) reduce the distance that signals can travel, by repackaging any molecules released outside of synapses.

Question 5

Neurons that release a neurotransmitter extrasynaptically

A) do not contain synaptic structures.
B) also release the same neurotransmitter synaptically.
C) may release the same or other neurotransmitters synaptically.
D) may have synaptic structures, which use a different neurotransmitter.
E) neurons do not communicate extrasynaptically - only glial cells do.

Question 6

In the lobster aggression system, the function of serotonin is such that serotonin

A) is not involved in aggressive behaviors in lobsters.
B) reduces the probability of any dominant or submissive behaviors.
C) increases the probability of a backward walking escape.
D) increases the strength and duration of dominant displays.
E) is required for any aggressive behaviors to be observed.

Question 7

The neurotransmitter responsible for 'tuning' the magnitude of aggressive displays in lobsters is

A) octopamine.
B) serotonin.
C) acetylcholine.
D) glutamate.
E) adrenaline.

Question 8

Experiments on extrasynaptic transmission using amperometry have demonstrated that

A) quantal packages of transmitter are released from the cell bodies of neurons.
B) neurotransmitters are released extrasynaptically without the use of vesicles.
C) vesicles at the soma are larger than those released at dendritic projections.
D) neurotransmitters are released from dendritic projections but not from the cell body.
E) only monoamines are released extrasynaptically.

Question 9

As a general rule, the mechanisms for extrasynaptic exocytosis

A) resemble exocytosis from gland cells in invertebrates, and resemble synaptic exocytosis in vertebrates.
B) have only been observed in vertebrates, and are similar to those of synaptic exocytosis.
C) are similar in invertebrates and vertebrates, and resemble exocytosis from gland cells.
D) resemble synaptic exocytosis in invertebrates, and resemble exocytosis from gland cells in vertebrates.
E) have only been observed in invertebrates, and are similar to exocytosis from gland cells.

Question 10

Which of the options below is not a method of extrasynaptic exocytosis?

A) Somato-dendritic exocytosis
B) Axonal exocytosis
C) Perisynaptic exocytosis
D) Perivascular exocytosis
E) Spillover

Question 11

Which of the options below is not a method of extrasynaptic exocytosis?

A) Fusion of large numbers of vesicles at the soma
B) Molecule release from clusters of vesicles from varicosities along non-myelinated axons
C) Molecules not stored in vesicles are gradually leaked from dendritic varicosities
D) Leak of excess transmitter from the synaptic cleft
E) Vesicles that are not part of the synaptic pool are released near presynaptic active zones

Question 12

Dense-core vesicles are often found

A) near somatic and perisynaptic release sites.
B) in the nucleus of dopaminergic neurons.
C) diffusing through the CSF.
D) in axon terminals of magnocellular neurons.
E) in retinal amacrine cells.

Question 13

Magnocellular hypothalamic neurons release _______ from the axons or dendrites.

A) either oxytocin or vasopressin
B) either dopamine or serotonin
C) acetylcholine
D) either epinephrine or norepinephrine
E) glutamate

Question 14

Tannic acid can be added to neurons in order to

A) produce fluorescence in peptides.
B) block the fusion of vesicles with the cell membrane.
C) count quanta of neurotransmitter released from different locations.
D) prevent reuptake of neurotransmitters.
E) visualize fusion of dense-core vesicles.

Question 15

Studies of hypothalamic magnocellular neurons have used radioimmunoassay to show that

A) vesicles may travel long distances from release sites to receptor sites.
B) magnocellular neurons are able to synthesize and release more than one peptide at once.
C) more vesicles are released at cell bodies than at dendrites.
D) trains of action potentials are needed to produce exocytosis.
E) extrasynaptic transmission uses dense-core, rather than clear, vesicles.

Question 16

In magnocellular neurons of the hypothalamus, oxytocin released from dendrites

A) mingles with synaptically released oxytocin to amplify its effects.
B) affects calcium release in neighboring neurons without altering electrical activity.
C) moves directly into the bloodstream for wide dissemination.
D) is sufficient to produce action potentials in neighboring neurons.
E) inhibits vesicle fusion at synaptic sites.

Question 17

One similarity between extrasynaptic transmission and synaptic transmission is that

A) both occur with a time lag of seconds to tens of seconds.
B) in both cases, vesicles are stored and docked adjacent to the cell membrane.
C) both may transmit molecules across short or long distances to receptor sites.
D) both release signaling molecules from vesicles by exocytosis.
E) both can be stimulated by a single action potential in the releasing neuron.

Question 18

In the somatic release sites of leech Retzius neurons, when exocytosis is not occurring,

A) dense-core vesicles are linked to the plasma membrane by microtubules.
B) clear vesicles are stored in the nucleus until they are needed for exocytosis.
C) both dense-core and clear vesicles are docked on structures along the cell membrane.
D) dense-core vesicles and mitochondria are clustered along the inside of the cell membrane.
E) multivesicular bodies are stored in the nucleus until they are needed for exocytosis.

Question 19

The fluorescent dye FM1-43 can be injected into the extracellular medium in order to visualize

A) the location where vesicles fuse to the plasma membrane.
B) microtubule transport systems.
C) monoamines in the extracellular space.
D) the location of mitochondria.
E) hormones in the blood stream.

Question 20

A measure of "FM1-43 fluorescent spots" can be used to indicate

A) ATP levels.
B) depolarization.
C) oxygen use of a neuron.
D) amount and location of exocytosis.
E) intracellular calcium levels.

Question 21

Electrical stimulation of leech Retzius neurons leads to

A) exocytosis, but only with low frequency stimulation (e.g., 1 Hz).
B) transport of vesicles to the plasma membrane, but only with high-frequency stimulation (e.g., 20 Hz).
C) exocytosis that is independent of the frequency of stimulation.
D) opening of calcium channels, but only with low frequency stimulation (e.g., 1 Hz).
E) inactivation of calcium channels that is independent of the frequency of stimulation.

Question 22

When measuring intracellular calcium levels of leech Retzius neurons, high-frequency stimulation (e.g. 20 Hz) of the neuron

A) leads to a later, slower peak than low-frequency stimulation.
B) produces a jagged, shark-tooth pattern with low peaks.
C) leads to a faster, higher peak concentration than low-frequency stimulation.
D) produces a gradual, roughly linear increase in concentration.
E) has no measurable effect on calcium concentration.

Question 23

L-type calcium channels, such as those found in the soma of leech Retzius neurons, are especially suitable for extrasynaptic signaling because they

A) open only after a lag of up to one second.
B) have a very high depolarization threshold for opening.
C) are permeable to magnesium as well as calcium.
D) inactivate rapidly after opening.
E) are not easily inactivated.

Question 24

In leech Retzius neurons, microtubules and kinesin motors function to

A) transport vesicles from the interior of the cell to the periphery.
B) transport vesicles from the nucleus to the axon terminals.
C) assist with reuptake and repackaging of vesicles.
D) dock vesicles to the cell membrane at release sites.
E) move receptors to active sites.

Question 25

Which of the sequences below best characterizes the sequence of events for somatic exocytosis in the leech Retzius neuron?

A) Transport of vesicles to plasma membrane; fast calcium transient; exocytosis; internal calcium release
B) Fast calcium transient; transport of vesicles to plasma membrane; internal calcium release; exocytosis
C) Internal calcium release; transport of vesicles to plasma membrane; exocytosis; fast calcium transient
D) Fast calcium transient; internal calcium release; transport of vesicles to plasma membrane; exocytosis
E) Internal calcium release; fast calcium transient; transport of vesicles to plasma membrane; exocytosis

Question 26

In the leech Retzius neuron, the direct effect of the fast calcium transient is to

A) open sodium channels.
B) inactivate potassium channels.
C) induce synthesis of ATP.
D) depolarize the neuron.
E) bind to NMDA receptors.

Question 27

Somatic exocytosis in the leech Retzius neuron is produced by intracellular calcium that is released in response to

A) dopamine.
B) acetylcholine.
C) octopamine.
D) serotonin.
E) oxytocin.

Question 28

The sequence of events by which serotonin produces somatic exocytosis in the leech Retzius neuron can best be characterized as

A) a negative feedback loop.
B) a positive feedback loop.
C) lateral inhibition.
D) a command center.
E) a central pattern generator.

Question 29

Unlike the recycling of vesicles at synapses, recycling of vesicles for somatic exocytosis

A) occurs in the Golgi apparatus.
B) occurs in the endoplasmic reticulum.
C) occurs in the extracellular space.
D) does not occur.
E) while docked at the plasma membrane.

Question 30

The main function of the Leech Retzius Neurons is to

A) initiate feeding behavior.
B) stimulate release of oxytocin and/or vasopressin.
C) synchronize motoneuron activity to command crawling behavior.
D) modulate aggressive behaviors.
E) inhibit release of octopamine.

Question 31

A scientist is studying leech behavioral neurobiology. If she injects serotonin into the leech, what is the scientist likely to observe?

A) The leech will not react appropriately to social cues.
B) The leech will produce a dominant display.
C) The leech will begin feeding.
D) The leech will contract (shorten) and become immobile.
E) The leech will begin crawling.

Question 32

An exosome is a

A) type of multivesicular body.
B) type of extracellular vesicle.
C) dense-core vesicle found in leech Retzius neurons.
D) tubulovesicular structure.
E) serotonin reuptake device.

Question 33

Transmitter spillover effects originate with

A) glial cells.
B) leakage of neurotransmitter from somatic exocytosis.
C) leakage of neurotransmitter from synaptic exocytosis.
D) disintegration of extracellular vesicles.
E) blockade of calcium channels.

Question 34

Dopamine is able to shift light sensitivity in the visual system by communicating with

A) optic nerve activity.
B) muscles regulating pupil constriction.
C) capillary dilation.
D) photoreceptors.
E) horizontal and amacrine cells.

Question 35

ATP acts on these cells in order to produce vasodilation in the retina.

A) Retzius neurons
B) Amacrine cells
C) Müller cells
D) Ependymal cells
E) Magnocellular neurons

Question 36

The structure of Müller cells is specialized in that

A) their end feet wrap around capillaries.
B) their cilia protrude into the CSF.
C) they contain photopigments.
D) they change in diameter in response to light.
E) they contain multivesicular bodies.

Question 37

When a Müller cell is stimulated with ATP, this leads to

A) influx of Na⁺ followed by an action potential.
B) the production of IP₃ and release of intracellular calcium.
C) phosphorylation and inactivation of potassium channels.
D) the release of dopamine into the CSF.
E) somatic exocytosis.

Question 38

The exchange of molecules across the ependymal cell layer is central to the process of

A) swimming behavior in leeches.
B) social dominance in lobsters.
C) light and dark adaptation.
D) long-distance communication via the CSF.
E) vasodilation in the retina.

Question 39

The movement of signaling molecules through the CSF represents one example of

A) volume transmission.
B) synaptic transmission.
C) retrograde messaging.
D) second messenger systems.
E) extrasynaptic potentiation.

Question 40

Ependymal cells are primarily found

A) lining the central canal of the spinal cord and the ventricles.
B) in the retina.
C) in the hypothalamus.
D) in the leech abdomen.
E) in the drosophila neuromuscular junction.

Question 41

Which of the options below is not a feature of one or more of the ependymal cell types?

A) Cilia that help drive movement of the CSF
B) Production of CSF
C) End feet that wrap around capillaries
D) Endocytosis of molecules from the CSF
E) Projections that release molecules into the neuropil

Question 42

The three processes contributing to the exchange of signaling molecules between the CSF and the CNS include: diffusion via perivascular pumping, selective uptake and release by neuronal structures, and

A) cilial beating by Müller cells.
B) release of molecules into the blood stream.
C) diffusion over short distances.
D) endocytosis of molecules from the CSF.
E) somatic exocytosis.

Question 43

A primary function of perivascular pumping is to

A) transmit ATP to Müller cells.
B) stimulate mechanosensory cilia on ependymal cells.
C) modulate the rate of blood flow in the retina.
D) increase the rate at which molecules can move through the CSF.
E) increase oxygen levels in the CSF.

Question 44

Briefly explain what volume transmission is.

Question 45

Describe the role of serotonin on aggressive displays by lobsters.

Question 46

Describe one method used by researchers to determine where extrasynaptic transmission occurs.

Question 47

What signaling molecules are released by magnocellular hypothalamic neurons, and from where are they released?

Question 48

What is the role of L-type calcium channels in the leech Retzius neuron?

Question 49

What are the three steps in the feedback loop that helps to maintain somatic exocytosis in leech Retzius neurons?

Question 50

What is one way in which recycling of dense core vesicles during extracellular exocytosis differs from recycling in standard synaptic transmission?

Question 51

What are "tripartite synapses" and how are they involved in extrasynaptic communication?

Question 52

Explain how spillover effects contribute to extrasynaptic communication.

Question 53

Briefly describe the function of extrasynaptic dopamine release in the retina.

Question 54

What is the function of Müller cells in the retina?

Question 55

Name two types of glial cells involved in extrasynaptic communication, and briefly explain what those cells do.

Question 56

What three components allow the CSF to enable long-distance signal transmission?

Question 57

What is the function of the ependymal cell layer?

Question 58

What are the three ways that the CNS and CSF exchange signaling molecules?