Question

The first thing that occurs when the axon terminal releases ACh is ________.

A. calcium ions return to the terminal cisternae of the SR
B. the troponin blocks the tropomyosin
C. calcium diffuses into the axon terminal of the motor neuron
D. diffusion of ACh across the synaptic cleft

Answer 1

It diffuses across the synaptic cleft to bind with synaptic receptors on the post-synaptic neuron . This cause influx of sodium ions though the ligand gated sodium channels into the synaptic cleft for depolarization. If this is upto to the threshold levels it generate Excitatory Post Synaptic Potential(EPSP) . However if at neuromuscular junction the acetycholine will diffuse across the cleft and bind with receptors (Nicotinic receptors) on the motor end plate to cause sodium influx. This generate action potential if up to the threshold and therefore muscle contraction.

Step-by-step explanation: