PRACTICE QUESTIONS

1. At the neuromuscular junction, Ca²⁺ ions are necessary for:

a. Binding the transmitter with the postsynaptic receptor.

b. Facilitating diffusion of the transmitter to the post­synaptic membrane.

c. Splitting the transmitter in the cleft, thus deactivat­ing the transmitter.

d. Fusing the presynaptic vesicle with the presynaptic membrane, thus releasing the transmitter.

e. Metabolizing the transmitter within the presynaptic vesicle.

2. A drug that would prevent the release of acetylcholine at the neuromuscular junction would cause what, if any, clinical signs?

a. Convulsions and excess muscle contractions

b. Paralvsis

c. No effect on an animal’s movement

3. Which one of the following is true with regard to the termination of synaptic action at the neuromuscular junction?

a. The reuptake of intact acetylcholine molecules into the motor neuron terminal is responsible.

b. Diffusion of acetylcholine away from the synapse is solely responsible.

c. Acetylcholinesterase rapidly breaks down acetyl­choline into choline and acetate.

d. Dissociation of acetylcholine from the muscarinic receptor, after binding for several seconds, is solely responsible.

Several drugs compete with acetylcholine for the post- synaptic receptor at the neuromuscular junction. If you overdosed your patient with one of these competi­tive drugs, what would the antidote need to do at the synapse?

a. Decrease the release of acetylcholine.

b. Decrease the effectiveness of acetylcholinesterase.

c. Decrease the influx of Ca² ’ into the motor neuron terminal.

d. Decrease the action potential frequency on the motor neuron.

e. None of the above.

5. Which of the following statements regarding neuron- to-neuron synapses is false?

a. The postsynaptic membrane is always a dendrite.

b. Dendritic spines increase the surface area of the postsynaptic membrane.

c. A single action potential on a presynaptic neuron is usually not sufficient to produce an action potential on a postsynaptic neuron.

d. The neurotransmitter is not always released from a morphologically distinct active zone of the presynaptic terminal.

e. Depending on the presynaptic neurotransmitter released and the postsynaptic receptor activated, the postsynaptic membrane can be either depolarized or hyperpolarized.