Question 1

Which enzyme is responsible for the hydrolysis of acetylcholine in the synaptic cleft, terminating its action?

Accepted Answer

Acetylcholinesterase

Question 2

A patient is administered reserpine. What is the primary effect of this drug on noradrenergic transmission?

Accepted Answer

It blocks the transport of noradrenaline into vesicles for storage.

Question 3

Which of the following best describes the role of calcium ions ($$Ca^{2+}) in $$neurotransmitter release at the nerve terminal?

Accepted Answer

They trigger the fusion of synaptic vesicles with the terminal membrane, leading to exocytosis of neurotransmitter.

Question 4

Which drug increases neurotransmitter release by blocking $$K^+$$ channels at the nerve terminal?

Accepted Answer

4-aminopyridine (4-AP)

Question 5

What is the rate-limiting step in the synthesis of noradrenaline?

Accepted Answer

Conversion of tyrosine to DOPA by tyrosine hydroxylase

Question 6

A patient overdoses on cocaine. Which step in noradrenergic transmission is most directly affected?

Accepted Answer

Reuptake of noradrenaline into the presynaptic terminal (uptake 1)

Question 7

Which of the following is a correct sequence of events for acetylcholine (ACh) release at the neuromuscular junction?

Accepted Answer

Action potential → $$Ca^{2+}$$ influx → fusion of vesicles → exocytosis of ACh

Question 8

Which enzyme metabolizes noradrenaline in the axoplasm of the nerve terminal?

Accepted Answer

Monoamine oxidase (MAO)

Question 9

A drug blocks voltage-sensitive $$Ca^{2+}$$ channels at the nerve terminal. What is the expected effect on neurotransmitter release?

Accepted Answer

Decreased neurotransmitter release due to inhibition of vesicle fusion

Question 10

Which of the following drugs acts as a monoamine oxidase (MAO) inhibitor at the noradrenergic nerve terminal?

Accepted Answer

Tranylcypromine

Question 11

What is the fate of acetylcholine after it acts on postsynaptic receptors at the neuromuscular junction?

Accepted Answer

It is hydrolyzed by acetylcholinesterase into choline and acetate.

Question 12

Which of the following drugs blocks the synthesis of noradrenaline?

Accepted Answer

α-methyl-p-tyrosine

Question 13

Which process is directly responsible for the termination of noradrenaline action in the synaptic cleft?

Accepted Answer

Reuptake into the presynaptic terminal (uptake 1)

Question 14

A patient is given 4-aminopyridine (4-AP) to treat muscle weakness. What is the mechanism by which this drug increases neurotransmitter release?

Accepted Answer

It blocks $$K^+$$ channels, prolonging depolarization and increasing neurotransmitter release.

Question 15

Which of the following is a correct description of the role of $$K^+$$ channels in the nerve terminal during neurotransmission?

Accepted Answer

Opening of $$K^+$$ channels causes repolarization, restoring the resting membrane potential.

Question 16

Which of the following drugs stimulates the release of noradrenaline from nerve terminals?

Accepted Answer

Tyramine

Question 17

Which protein is responsible for packaging acetylcholine into synaptic vesicles?

Accepted Answer

Vesicular acetylcholine transporter (VAT)

Question 18

A patient is treated with tricyclic antidepressants. What is the effect of these drugs on noradrenergic transmission?

Accepted Answer

They block the reuptake of noradrenaline into the presynaptic terminal.

Question 19

Which of the following is a consequence of blocking $$Ca^{2+}$$ channels at the nerve terminal using cadmium ($$Cd^{2+}$$)?

Accepted Answer

Decreased neurotransmitter release

Question 20

Which enzyme is responsible for the methylation of noradrenaline in the synapse?

Accepted Answer

Catechol-O-methyltransferase (COMT)

Neurotransmission and Pharmacological Modification in the Peripheral Nervous System

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