Question

multiple choice 2 points
which of these happens first in a cholinergic synaptic transmission?
a postsynaptic potential is produced.
the synaptic vesicles release acetylcholine.
acetylcholine binds to ligand-regulated gates.
acetylcholine diffuses across the synaptic cleft.
sodium enters the postsynaptic cell.

Explanation:

Analyze the sequence of cholinergic synaptic transmission

Using the Neuromuscular Junction and Acetylcholine Receptors knowledge points, we trace the chronological order of events during a cholinergic synaptic transmission:

1. The synaptic vesicles release acetylcholine (ACh is released into the synaptic cleft via exocytosis).
2. Acetylcholine diffuses across the synaptic cleft (ACh travels across the physical gap).
3. Acetylcholine binds to ligand-regulated gates (ACh binds to nicotinic receptors on the postsynaptic membrane).
4. Sodium enters the postsynaptic cell (Ligand-gated channels open, allowing \(Na^+\) influx).
5. A postsynaptic potential is produced (The influx of positive ions depolarizes the membrane, creating a local potential).

Identify the earliest event among the options

Comparing the given options to the established chronological sequence:

• "The synaptic vesicles release acetylcholine" is step 1.
• "Acetylcholine diffuses across the synaptic cleft" is step 2.
• "Acetylcholine binds to ligand-regulated gates" is step 3.
• "Sodium enters the postsynaptic cell" is step 4.
• "A postsynaptic potential is produced" is step 5.

Therefore, the event that happens first among the choices is the release of acetylcholine from synaptic vesicles.

Answer:

• (A) A postsynaptic potential is produced
• (B) The synaptic vesicles release acetylcholine (Correct answer)
• (C) Acetylcholine binds to ligand-regulated gates
• (D) Acetylcholine diffuses across the synaptic cleft
• (E) Sodium enters the postsynaptic cell