Deck 15: Transmitter Synthesis, Storage, Transport, and Inactivation

Question 1

Unlike low-molecular-weight transmitters, neuropeptides are synthesized in

A) the cell body and packaged in dense-core vesicles for transport.
B) the axon terminals and not packaged into vesicles.
C) the cell body and not packaged into vesicles.
D) dendrites and somatic varicosities and packaged into small synaptic vesicles for transport.
E) the axon terminals and packaged in dense-core vesicles.

Answer 1

A

Question 2

Nictric oxide, carbon monoxide, and endocannabinoids are unusual among molecular messengers in that they are

A) not synthesized by the body but are ingested directly.
B) synthesized in terminals but are not packaged into vesicles.
C) synthesized in the cell body rather than in axon terminals.
D) packaged in dense-core vesicles rather than synaptic vesicles.
E) packaged into vesicles containing multiple messengers.

Answer 2

B

Question 3

Compared with the synthesis of low-molecular-weight neurotransmitters, the synthesis of peptides

A) is faster and more efficient.
B) occurs nearer to release sites.
C) occurs inside of vesicles.
D) is slower and quantities are more limited.
E) does not involve enzymes.

Answer 3

D

Question 4

Unlike low-molecular-weight neurotransmitters, peptides are synthesized

A) on ribosomes.
B) inside of vesicles.
C) in the axon terminals.
D) outside of the CNS.
E) in the extracellular space.

Question 5

If preganglionic neurons are stimulated such that ACh is released from ganglionic neurons at a high level, these neurons become depleted

A) after a few (3-7) seconds of stimulation.
B) after a few (3-7) minutes of stimulation.
C) after about 20-30 minutes of stimulation.
D) in less than an hour.
E) after more than an hour.

Question 6

ChAT and AChE are

A) two components of ACh receptors.
B) molecules that assist with docking vesicles to the cell membrane.
C) the two molecules from which ACh is synthesized.
D) enzymes responsible for the synthesis and the degradation of ACh.
E) molecules responsible for the packaging of ACh into vesicles.

Question 7

Acetylcholine is synthesized by _______ and degraded by _______.

A) choline; ChAT
B) AChE; AcCoA
C) HC-3; AChE
D) ChAT; AChE
E) AcCoA; ChAT

Question 8

The ingredients or precursors required for the synthesis of acetylcholine are sourced from

A) glial cells.
B) the cell body.
C) the extracellular fluid and the mitochondria.
D) they are synthesized in the synaptic terminal.
E) the diet.

Question 9

If ChAT in the cytoplasm is inhibited, the predicted effect would be

A) an accumulation of high levels of ACh.
B) a depletion in ACh levels.
C) the release of excessive levels of ACh from the synapse.
D) an accumulation of ACh outside of vesicles, but a decrease in ACh-packed vesicles.
E) an inability of vesicles containing ACh to fuse with the synaptic membrane.

Question 10

The accumulation of ACh levels in a synaptic terminal is limited or reduced by increasing activity of

A) ATP.
B) AcCoA.
C) AChE.
D) VAChT.
E) ChAT.

Question 11

Identification of the rate-limiting step in the synthesis of norepinephrine was achieved by measuring the

A) activity of dopamine -hydroxylase in the presence of varying levels of dopamine.
B) amount of DOPA produced after inhibition of tyrosine hydroxylase.
C) amount of each relevant enzyme in the cytoplasm.
D) amount of norepinephrine produced when the preparation was bathed in various precursors.
E) amount of norepinephrine produced when various enzymes were inhibited.

Question 12

Compared to other neurotransmitters, serotonin synthesis is especially dependent on the levels of precursors made available through

A) reuptake.
B) mitochondria.
C) the diet.
D) hydrolyzation.
E) synthesis in the cell body.

Question 13

GABA is synthesized from

A) glutamate by the enzyme GAD.
B) GAD by the enzyme -ketoglutarate.
C) glutamic acid by the enzyme decarboxylase.
D) ATP by the enzyme GABA hydroxylase.
E) GAD by the enzyme adenosine triphosphate.

Question 14

An experimental increase in the availability of glutamic acid decarboxylase (GAD) would be expected to produce a(n)

A) increase in GABA.
B) reduction in GABA.
C) increase in glutamate.
D) increase in glutamine.
E) reduction in glutamine.

Question 15

In the synthesis cycle of glutamate, an increase in the activity of glutaminase would be predicted to lead to a(n)

A) increase in glutamate and a reduction in glutamine.
B) increase in glutamine and a reduction in glutamate.
C) increase in both glutamine and glutamate.
D) reduction in both glutamine and glutamate.
E) reduction in glutamate and no change in glutamine.

Question 16

In the synthesis cycle of glutamate, it is generally the case that

A) neurons convert glutamate to glutamine, while glial cells convert glutamine to glutamate.
B) neurons convert glutamine to glutamate, while glial cells convert glutamate to glutamine.
C) neurons convert glutamine to glutamate, which is then hydrolyzed by glutaminase in the synaptic cleft.
D) glial cells convert glutamine to glutamate which is then recycled into the presynaptic neuron through reuptake.
E) glial cells convert glutamine to glutamate, which is then hydrolyzed by GAD before diffusing away.

Question 17

Imagine a hypothetical pathway in which precursor X and precursor Y are combined by enzyme Z in order to produce neurotransmitter XYZ. Which of the choices below would represent feedback inhibition?

A) Increasing levels of X or of Y lead to a reduction in activity of enzyme Z.
B) Increasing levels of enzyme Z lead to an increase in levels of XYZ.
C) Increasing levels of enzyme Z lead to a reduction in availability of X and Y.
D) Increasing levels of XYZ lead to an increase in the availability of X.
E) Increasing levels of XYZ lead to a reduction in the activity of enzyme Z.

Question 18

Imagine a hypothetical pathway in which precursor X and precursor Y are combined by enzyme Z in order to produce neurotransmitter XYZ. You observe that as levels of XYZ increase in the cytoplasm, the activity of enzyme Z slows down. This is an example of

A) positive feedback.
B) feedback inhibition.
C) retrograde transport.
D) anterograde synthesis.
E) a rate limiting step.

Question 19

Which of these correctly represents the sequence of norepinephrine synthesis?

A) AAD, dopamine, epinephrine, norepinephrine
B) DOPAC, dopamine, norepinephrine
C) Tyrosine, dopamine, epinephrine, norepinephrine
D) DOPA, epinephrine, norepinephrine
E) Tyrosine, DOPA, dopamine, norepinephrine

Question 20

Feedback inhibition can be observed in the synthesis of norepinephrine through the

A) inhibition of tyrosine hydroxylase by norepinephrine.
B) degradation of dopamine by DOPAC.
C) availability of dopamine -hydroxylase.
D) inhibition of AAAD by DOPA.
E) synthesis of norepinephrine by dopamine -hydroxylase.

Question 21

Imagine that a hypothetical neurotransmitter, neurotran-X (NTX), is synthesized from two ingredients, neuro-A and tran-B. An enzyme, neurotranoxylase (NTO), is responsible for producing neurotran-X from the two ingredients. If the rate of synthesis of NTX is controlled through feedback inhibition, you would expect to observe experimentally

A) increasing levels of NTO will lead to increased levels of NTX.
B) reducing levels of neuro-A will reduce levels of NTX.
C) increasing levels of NTX will lead to reduced activity of NTO.
D) reducing levels of neuro-A will lead to reduced activity of NTO.
E) reducing levels of NTX will lead to reduced activity of NTO.

Question 22

Scientists are attempting to characterize a novel neurotransmitter, neurotran-Y (NTY), which is synthesized by the enzyme neuro-y-oxidase (NYO) from a precursor, neuro-A. In an experiment they inject artificially high levels of NTY into the pre-synaptic terminal of a cell that releases NTY. Shortly thereafter, they measure the activity of NYO and observe that its activity has been suppressed. The scientists have found evidence for

A) reuptake.
B) hydrolyzation.
C) co-transmission.
D) feedback inhibition.
E) fast axonal transport.

Question 23

When animals are subjected to stress, prolonged activation of the sympathetic nervous system results in a(n)

A) increase in production of enzymes that degrade neurotransmitters, such as MAO.
B) reduction in the numbers of enzymes that degrade neurotransmitters, such as ADH.
C) increase in production of enzymes used for neurotransmitter synthesis, such as TH.
D) increase in the numbers of enzymes used for neurotransmitter synthesis, such as ATPase.
E) increase in the availability of precursors such as tryptophan.

Question 24

Long-term changes to the rate of neurotransmitter synthesis can be observed in response to

A) prolonged activation of the sympathetic nervous system due to stress.
B) availability of the neurotransmitter in the synaptic terminal.
C) availability of the neurotransmitter in the extracellular space.
D) chronic changes to glutamine availability in the diet.
E) changes in the composition of gut microbiota.

Question 25

One of the mechanisms through which long-term changes to the rate of neurotransmitter synthesis are achieved is

A) the production of new receptors for neurotransmitter reuptake.
B) the synthesis of new enzymes involved in neurotransmitter production.
C) the production of g-protein coupled receptors used for inhibitory feedback.
D) a reduction in the electrical excitability of neurons.
E) an increase the efficiency with which neurotransmitters are packed into vesicles.

Question 26

Relatively small quantities of neuropeptides are required for signaling, in part because

A) they have a much higher affinity for their receptors than low-molecular-weight transmitters.
B) they are synthesized so quickly that a continuous supply is available.
C) one molecule can typically bind to many receptors at a time.
D) the binding sites are extremely close to the release sites.
E) their metabotropic receptors can amplify the signal through intracellular pathways.

Question 27

Low-molecular-weight transmitters are packaged in _______, while neuropeptides are packaged in _______.

A) small, dense-core vesicles; large, clear vesicles
B) small, clear vesicles; large, clear vesicles
C) large vesicles in the cell body; small vesicles in the axon terminal
D) large vesicles in the cytoplasm; small vesicles in the soma
E) small, clear vesicles; large, dense-core vesicles

Question 28

The functions of proteins such as VAChTs, VGLUT1, and VIAAT is to

A) degrade neurotransmitters into simpler molecules.
B) transport vesicles along microtubules.
C) package neurotransmitters into vesicles.
D) synthesize neurotransmitters from precursors.
E) facilitate diffusion away from the synaptic cleft.

Question 29

One important feature of the transport proteins used to package neurotransmitters into vesicles is that

A) they often have low specificity and may transport more than one type of neurotransmitter.
B) one type of protein transports the low-molecular-weight transmitters, and a second type transports neuropeptides.
C) they are usually saturated and serve as the rate-limiting factor for the availability of vesicles.
D) they may also be present in the cell membrane and transport neurotransmitters directly into the extracellular space.
E) they are highly efficient so that little neurotransmitter can be found outside of vesicles.

Question 30

The concentration or quantity of a neurotransmitter in each vesicle

A) is constant across all neurons for a given neurotransmitter.
B) is constant for vesicles using a given transport protein.
C) may vary between neurons, but is constant within a neuron for a given neurotransmitter.
D) may vary based on availability of the transmitter and concentration of chloride ions.
E) may vary based on the availability of enzymes used in synthesis.

Question 31

Which best illustrates the concept of "co-transmission"?

A) A single vesicle contains both glycine and GABA, and releases both synchronously
B) A synaptic terminal contains some vesicles with dopamine, and some with norepinephrine, that are released simultaneously
C) A synaptic terminal contains some vesicles with dopamine, and some with norepinephrine, that are released at different times based on different patterns of activity
D) Both a and b
E) a.b and c

Question 32

A primary difference between axoplasmic flow and axonal transport is that axonal transport

A) is much faster than axoplasmic flow.
B) moves from the cell body to the axons.
C) primarily transports structural proteins.
D) is much slower than axoplasmic flow.
E) is difficult to observe through tracing or labeling.

Question 33

The movement of organelles and proteins toward the axon terminal is called _______ while the movement toward the cell body is called _______.

A) top-down transport; bottom-up transport
B) anterograde transport; retrograde transport
C) axoplasmic flow; somatoplasmic flow
D) retrograde transport; anterograde transport
E) axonal transport; somatic transport

Question 34

Fast axonal transport is powered by

A) kinesin and cytoplasmic dynein motors.
B) diffusion.
C) cilial beating.
D) electrical currents.
E) all of the above.

Question 35

When organelles such as mitochondria and vesicles bind to microtubules to travel toward axon terminals, they move at a rate

A) substantially slower than the background movement of cytoplasm.
B) about the same as the background movement of cytoplasm.
C) substantially faster than the background movement of cytoplasm.
D) substantially slower than transport to the cell body.
E) substantially faster than transport to the cell body.

Question 36

Anterograde axonal transport is powered by _______ while retrograde transport is powered by _______.

A) myosins; kinesin
B) axoplasmic flow; myosins
C) kinesin; cytoplasmic dynein
D) microtubules; myosins
E) cytoplasmic dynein; axoplasmic flow

Question 37

Microtubules play an essential role in

A) removing neurotransmitter from the synaptic cleft.
B) packaging neurotransmitters in vesicles.
C) axoplasmic flow.
D) fast axonal transport.
E) slow axonal transport.

Question 38

The functional outcome of a common class of drugs, monoamine oxidase (MAO) inhibitors, is to

A) reduce the availability of neurotransmitters such as acetylcholine and ATP in the brain.
B) increase the availability of neurotransmitters such as dopamine and norepinephrine in the brain.
C) reduce the availability of neurotransmitters such as dopamine and norepinephrine in the brain.
D) increase the availability of neurotransmitters such as GABA and glycine in the brain.
E) reduce the availability of serotonin in the brain.

Question 39

The duration of ACh activity at postsynaptic receptor sites is limited by

A) a high concentration of AChE in the synaptic cleft.
B) a high concentration of intracellular AChE in the presnaptic terminal.
C) a large number of reuptake receptors on the pre-synaptic membrane.
D) the proximity of glial cells that absorb the ACh .
E) the size of vesicles released from the presynaptic terminal.

Question 40

The action of peptide transmitters appears to be terminated primarily through

A) enzymatic degradation.
B) synthesis into new molecules.
C) uptake into neighboring glial cells.
D) reuptake into the pre-synaptic terminals.
E) diffusion.

Question 41

Inhibition of acetylcholinesterase in the synaptic cleft of a neuromuscular junction results in a(n)

A) reduction in the ACh available at the postsynaptic receptor.
B) substantial increase in the duration of the postsynaptic potential.
C) increase in choline available for synthesis inside the neuron.
D) substantial reduction in the amplitude of the postsynaptic potential.
E) significant delay in the latency of the postsynaptic response.

Question 42

Describe two differences between the synthesis and packaging of peptides compared to low-molecular-weight neurotransmitters.

Question 43

Given what you know about the synthesis of acetylcholine, name two ingredients that could be added to a neuron in order to increase acetylcholine availability in the cell.

Question 44

Predict what would happen if you experimentally increase levels of GAD in a brain slice preparation.

Question 45

Give one example of feedback inhibition in the synthesis of neurotransmitters, and explain why the example illustrates this effect.

Question 46

Give one example of long-term regulation of neurotransmitter synthesis.

Question 47

Why is it that only a small quantity of a peptide is needed to produce activity in a target cell?

Question 48

Some of the proteins that are responsible for packaging neurotransmitters into vesicles bind to more type of molecule. Give an example of an effect of this nonspecificity.

Question 49

What is one way in which synaptic plasticity could be accomplished through co-transmission?

Question 50

What is the difference between anterograde transport and retrograde transport, and what do the two have in common?

Question 51

Describe a major difference between slow axonal transport and fast axonal transport.

Question 52

What are three mechanisms used to remove transmitter from the synaptic cleft?

Question 53

Imagine that you are a scientist working to develop a drug that will increase acetylcholine signaling - specifically, your plan is to make more acetylcholine available at post-synaptic receptor sites. Based on your knowledge of neurotransmitter synthesis, storage, and degradation, provide one target mechanism that you could use to accomplish this goal.

Question 54

Given what you know about how the actions of neurotransmitters can be terminated, give two examples of how the effects of norepinephrine could be reduced at a synaptic receptor.

Question 55

Give two examples of how the synthesis, transport, and/or inactivation of peptides differs from that of typical low molecular weight neurotransmitters.

Question 56

What is the mechanism by which ATP and ACh are most often inactivated?