Deck 7: Acetylcholine

Question 1

Which statement about acetylcholine (ACh) synthesis is true?

A) The key catalyzing enzyme is acetylcholinesterase.
B) Choline, which is synthesized into ACh, comes from the diet and the liver.
C) Acetyl coenzyme A limits synthesis, as it is not found in all cells.
D) Coenzyme A is an important precursor.

Answer 1

B

Question 2

Neurons that use ACh as their transmitter can be identified by the presence of _______ in the cytoplasm of the cell.

A) acetylcholinesterase
B) acetyl coenzyme A
C) choline acetyltransferase
D) choline

Answer 2

C

Question 3

Manipulating acetylcholine synthesis with pharmacological agents

A) is straightforward because of the pharmacological specificity of ChAT inhibitors.
B) has led to significant clinical improvements in disorders like Alzheimer's disease.
C) may yield unfortunate side effects, such as a fishy odor, due to peripheral metabolism.
D) is straightforward because it relies entirely on the availability of precursors.

Answer 3

C

Question 4

In a cholinergic neuron, if ACh remains in the cytoplasm but is not moving into synaptic vesicles in the nerve terminal for storage, which of the following scenarios might be true?

A) The choline transporter is blocked by the drug hemicholinium-3.
B) The vesicular transporter VAChT is blocked by the drug vesamicol.
C) The choline transporter is blocked by the drug pyridostigmine.
D) The vesicular transporter VAChT is blocked by the drug donepezil.

Question 5

The drug vesamicol

A) blocks acetylcholinesterase.
B) decreases the amount of acetylcholine in the cytoplasm.
C) increases the rate of choline acetyltransferase activity.
D) decreases the release of acetylcholine from the nerve terminal.

Question 6

Which of the following is the most severe toxin involving acetylcholine?

A) Botulinum
B) Prairie rattlesnake venom
C) Hemicholinium-3 (HC-3)
D) Black widow spider venom

Question 7

Black widow spider venom produces its effects by _______, while botulinum toxin causes its effects by _______.

A) increasing metabolism of ACh; preventing release of ACh
B) blocking ACh receptors in the PNS; blocking ACh receptors in the CNS
C) preventing metabolism of ACh; increasing synthesis of ACh
D) causing massive release of ACh; preventing release of ACh

Question 8

Botulinum toxin has been used for all of the following except

A) cosmetic purposes (treatment of "dynamic wrinkles").
B) the treatment of facial and eyelid spasms.
C) the treatment OCD and autism.
D) the treatment of dystonias (prolonged muscle contractions).

Question 9

Which statement regarding botulinum toxin is false?

A) The bacterium grows in anaerobic environments.
B) It prevents fusion of the synaptic vesicles containing ACh with the presynaptic terminal.
C) It is a mixture of seven related proteins.
D) It is taken up by cholinergic neurons of the CNS.

Question 10

Which of the following represents the correct order of events at the neuromuscular junction?

A) AChE secreted by muscle cell → ACh metabolized into choline + acetic acid → choline transported back into terminal
B) ACh metabolized into choline + acetic acid → AChE secreted by cholinergic neuron → choline transported back into terminal
C) AChE secreted by muscle cell → ACh metabolized into choline + acetic acid → choline and acetic acid transported back into terminal
D) Choline transported to neuromuscular junction → AChE secreted by muscle cell → ACh metabolized into choline + acetic acid

Question 11

The choline transporter can be blocked by

A) vesamicol.
B) hemicholinium-3.
C) physostigmine.
D) pyridostigmine.

Question 12

Mutant mice lacking the choline transporter die within an hour or so of birth because they

A) synthesize too much ACh.
B) synthesize too little ACh.
C) suffer from a buildup of acetic acid.
D) cannot release ACh properly.

Question 13

Which of the following is not an AChE inhibitor?

A) HC-3
B) Neostigmine
C) Sarin
D) Organophosphorus insecticides

Question 14

The most important difference between pyridostigmine and sarin is that

A) pyridostigmine is an irreversible AChE inhibitor; sarin is not.
B) Pyridostigmine does not cross the blood-brain barrier; sarin does.
C) sarin is an irreversible AChE inhibitor; pyridostigmine is not.
D) pyridostigmine is isolated from Calabar beans; sarin is not.

Question 15

Pyridostigmine can be used as an antidote to sarin because

A) pyridostigmine acts on ACh release, not on its breakdown by AChE.
B) temporary interactions between pyridostigmine and AChE prevent it from being permanently inactivated by sarin.
C) pyridostigmine inactivates sarin by interacting with its ACh binding site.
D) pyridostigmine prevents sarin from crossing the blood-brain barrier.

Question 16

Which drug/action pairing is incorrect?

A) Vesamicol: inhibits vesicular uptake of ACh
B) Atropine: muscarinic receptor antagonist
C) Physostigmine: inhibits choline reuptake
D) Sarin: irreversibly inhibits AChE

Question 17

Why would the A12 form of AChE be of particular interest to a researcher whose focus was on motor impairments?

A) A12 leads to ACh release in brain areas involved in motor control.
B) A12 leads to ACh inhibition in brain areas involved in motor control.
C) A12 occurs at the neuromuscular junction where ACh is released by motor neurons to stimulate muscular contraction.
D) A12 release the neuromuscular junction inhibits ACh is release and ceases muscular contraction.

Question 18

The mode of action of drugs such as such as donepezil, rivastigmine, or galantamine, which are used to treat patients with dementia, is to _______ activity in the brain.

A) inhibit AChE
B) promote AChE
C) inhibit VAChT
D) promote VAChT

Question 19

Long-term exposure to the insecticides known as _______, which produce a nearly irreversible inhibition of AChE activity, is harmful to non-target species, including humans.

A) scopolamine
B) sarin
C) neonicitinoids
D) organophosphorus compounds

Question 20

Myasthenia gravis

A) involves a low production of acetylcholine.
B) is best treated by chemicals such as soman.
C) involves an autoimmune process that blocks acetylcholine receptors.
D) should be treated by neostigmine because it crosses the blood-brain barrier.

Question 21

The symptoms seen in genetic myasthenic syndromes are caused by genetic mutations that result in _______ activity and _______ at the at the neuromuscular junction.

A) increased ChAT; excessive release of ACh
B) lowered ChAT; insufficient release of ACh
C) increased l-dopa; insufficient release of dopamine
D) lowered l-dopa; excessive release of dopamine

Question 22

An individual with overactive bladder or bruxism (teeth grinding) may be prescribed a low dose of

A) succinylcholine.
B) atropine.
C) curare.
D) purified botulinum toxin A.

Question 23

Which statement about curare is false?

A) It produces anesthesia.
B) It produces paralysis and stops respiration.
C) It is used on the tips of arrows by native tribes in South America.
D) By taking it themselves, scientists determined that it does not reduce consciousness.

Question 24

Which brain area(s) is/are not part of the basal forebrain cholinergic system (BFCS)?

A) Diagonal band nuclei
B) Substantia innominata
C) Locus coeruleus
D) Medial septal nucleus

Question 25

LDTg and PPTg cells

A) are cholinergic interneurons.
B) send cholinergic projections to many forebrain structures.
C) utilize dopaminergic signals to control cholinergic cell function.
D) send cholinergic projections to the basal ganglia and thalamus, lower brainstem and spinal cord.

Question 26

Which of the following is thought to play a role in the deficits seen in motor control in people with Parkinson's disease?

A) Loss of forebrain cholinergic neurons
B) An imbalance between striatal cholinergic interneuron activity and dopaminergic input to the striatum
C) Excitation of midbrain dopamine neurons by the pontine cholinergic cells
D) Damage to the BFCS

Question 27

The drugs Cogentin and Artane are used cautiously to treat Parkinson's disease because of the potential side effect of

A) blocking dopamine receptors
B) increasing both acetylcholine and dopamine.
C) preventing cell death in late stages of the disorder.
D) blocking cholinergic receptors.

Question 28

Which mechanism is responsible for the pleasurable and rewarding effects of some drugs, such as cocaine and opioids?

A) The excitation of midbrain dopamine neurons by the pontine cholinergic cells
B) ACh release from postganglionic fibers of the parasympathetic nervous system
C) Phasic release of ACh in the prefrontal cortex
D) Stimulation of K⁺ channel opening by muscarinic receptors

Question 29

Because cholinergic interneurons are clustered in the _______, changes in cholinergic function can affect _______.

A) striatum; movement
B) thalamus; temperature regulation
C) amygdala; emotional responses
D) striatum; emotional responses

Question 30

Which statement about ACh and cognitive function is false?

A) Atropine produces amnesic effects.
B) Scopolamine produces amnesic effects.
C) Acetylcholine release is inhibited in prefrontal cortex when animals are presented with a sensory stimulus.
D) Alzheimer's disease is associated with a loss of cholinergic neurons in the forebrain.

Question 31

Rats that perform poorly in the 5-choice serial reaction time task, which tests sustained attention, would likely have deficits in ACh in which brain area?

A) Hippocampus
B) Cerebral cortex
C) Cerebellum
D) Brainstem

Question 32

Muscle nicotinic receptors

A) are found on muscle cells at the neuromuscular junction.
B) are metabotropic receptors.
C) can be overly stimulated by the poison d-tubocurarine.
D) possess two protein subunits, one α subunit and one β subunit.

Question 33

Which statement does not accurately describe activity at the nicotinic receptor?

A) The channel opens rapidly and depolarization occurs.
B) Sodium and calcium ions enter the next cell.
C) Prolonged stimulation of receptors can lead to desensitization.
D) Nicotinic receptors are found only on specific neurons in the brain.

Question 34

Activation of _______ nAChRs enhances neurotransmitter release from the nerve terminal by depolarizing it, and does not affect firing of the receiving cell.

A) presynaptic brain
B) postsynaptic brain
C) presynaptic muscle cell
D) postsynaptic muscle cell

Question 35

With continuous exposure to _______, nicotinic receptors become _______.

A) antagonist; desensitized
B) agonist; desensitized
C) antagonist; resensitized
D) agonist; blocked to depolarization

Question 36

A drug that produces a depolarization block of muscle cells is

A) muscarine.
B) succinylcholine.
C) nicotine.
D) d-tubocurarine.

Question 37

Which statement regarding muscarinic receptors is false?

A) They are metabotropic.
B) They all inhibit the formation of cAMP.
C) They can open potassium channels, causing inhibitory effects.
D) They are widely distributed in the brain.

Question 38

Muscarinic receptors in the brain play a role in all of the following except

A) motor function.
B) cognition.
C) digestion.
D) dependence and addiction.

Question 39

Activation of M₁, M₃, or M₅ receptors leads to _______ of the _______ cell, while activation of M₂ or M₄ receptors leads _______of the _______ cell.

A) inhibition; excitation; presynaptic; presynaptic
B) excitation; inhibition; presynaptic; presynaptic
C) inhibition; excitation; postsynaptic; postsynaptic
D) excitation; inhibition; postsynaptic; postsynaptic

Question 40

A muscarinic receptor acts by inhibiting of cAMP synthesis, stimulating K⁺ channel opening, and inhibiting nerve terminal Ca²⁺ channel opening. Which subtypes have these characteristics?

A) M₂ and M₃
B) M₂ and M₄
C) M₁ and M₃
D) M₃ and M₅

Question 41

In an experiment on muscarinic receptors, strains of rats that were ethanol-preferring (iP) received an _______ negative allosteric modulator and afterward showed reduced _______ behaviors.

A) M₁; aggressive
B) M₃; fearful
C) M₄; sedated
D) M₅; addictive

Question 42

Ingestion of a parasympathomimetic agent, such as pilocarpine, can cause all of the following except

A) sweating.
B) pupillary dilation.
C) salivation.
D) diarrhea.

Question 43

Nicotinic receptors found on muscle cells require binding of _______ molecules of ACh and are composed of _______ subunits, a _______ subunit, one ?, and either a ? or an ? subunit.

A) two; two ?1; ?1
B) five; two ?2; ?2
C) two to five; two ?1; ?1
D) two; two ?7; ?4

Question 44

One important feature of the presence of multiple, different nAChR subunits is that the subunits

A) vary among different individuals.
B) can "fill in" for one another, for example if one fails to function.
C) similarly affect how selective the channel is to different ions.
D) differentially affect how selective the channel is to different ions.

Question 45

Some of the _______ functions of ACh are thought to be due to activation of (α4)₂ (β2)₃ and (α7)₅ nicotinic receptors.

A) reflex
B) motor
C) cognitive
D) rewarding

Question 46

Muscle nAChR receptors have two α subunits and thus two ACh binding sites. Both binding sites must be occupied in order for the receptor channel to

A) open.
B) be desensitized.
C) close.
D) be selective.

Question 47

Describe the synthesis and breakdown of acetylcholine. Identify several beneficial and several harmful drugs that affect the metabolism of acetylcholine.

Question 48

Describe how storage and release of acetylcholine is affected by the following: vesamicol, black widow spider venom, and botulinum toxin. How is botulinum toxin being used in therapeutic and cosmetic settings today?

Question 49

Explain how a reversible AChE inhibitor like pyridostigmine can be used as an antidote of sorts against an irreversible AChE inhibitor, such as the nerve gas sarin.

Question 50

Describe the structure and function of the three main forms of AChE of the brain and peripheral nervous system.

Question 51

Why is brain nicotinic ACh receptor subunit composition the focus of much research? List the different ways that subunit composition affects receptor behavior.

Question 52

Write an informative and coherent paragraph incorporating the following terms: myasthenia gravis, ACh, skeletal muscle, neuromuscular junction, autoimmune disorder, neostigmine.

Question 53

Describe the location of muscarinic receptors in the brain and periphery. List two central and two peripheral functions of these receptors. Finally, name a parasympathomimetic agent and a parasympatholytic agent.

Question 54

Identify the cholinergic circuits in the central nervous system that are most important in cognitive functioning. How did optogenetic experiments on mice support involvement of these circuits in sustained attention?

Question 55

Describe the location and characteristics of nicotinic receptors. Name one drug that acts as an agonist and one drug that acts as an antagonist at these receptors.

Question 56

Describe the mechanism of action of neonicotinoid insecticides and the current controversy surrounding their use.