Question

1. when an impulse arrives at the synaptic knob of the motor neuron, calcium a) exits through ligand - gated channels and triggers neurotransmitter uptake. b) enters through voltage - gated channels and triggers the release of transmitter. c) exits through active transport pumps and brings neurotransmitter with it. d) is released from synaptic vesicles.

Explanation:

When an impulse reaches the synaptic knob of a motor neuron, the change in membrane potential opens voltage - gated calcium channels. Calcium ions then enter the cell through these channels. This influx of calcium triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft.

Answer:

B. enters through voltage - gated channels and triggers the release of transmitter.