Question #145

Which of the following statements regarding the mammalian neuromuscular junction is correct?

the nicotinic acetylcholine receptor ion channel is permeable to Na+ only

neuropeptides play key roles as neurotransmitters

the magnitude of postsynapic responses is decreased in the presence of cholinesterase inhibitors

discrete postsynaptic depolarizations occur even in the absence of presynaptic activity

curare acts by blocking presynaptic ion channels

Acetylcholine is the key transmitter at the mammalian neuromuscular junction. The postsynaptic receptor for this neurotransmitter, the nicotinic acetylcholine receptor, is a pentameric ion channel. It is permeable to both Na+ and Ca2+.

Discrete postsynaptic depolarization events are seen even in the absence of presynaptic activity and reflect the random release of quanta of neurotransmitter. Response magnitude is enhanced in the presence of cholinesterase inhibitors as each molecule of acetylcholine is present in the cleft for longer.

Any comments or corrections? Please e-mail help@cambridgequestions.co.uk