Complete each sentence with the correct word or phrase

a. An action potential reaches the axon terminal causing ________to open.
b. Acetylcholine diffuses across the synaptic cleft before binding to its receptor, which is located on the _
c. When the membrane potential reaches an action potential spreads across the sarcolemma due to the opening of _
d. In response to acetylcholine binding, ____ move into the muscle fiber causing the membrane potential to rise.

a). The voltage-gated [tex]Ca^{2+}[/tex] channels are the key transducers of the membrane potential that changes into a intracellular [tex]Ca^{2+}[/tex] transients which initiates the physiological events. When the action potential makes a contact with axon terminal, the voltage-gated [tex]Ca^{2+}[/tex] channels opens.

b). The acetylcholine is the main neurotransmitter of the parasympathetic nervous system. It helps in blood vessels dilation, muscle contraction, and perform many more functions.

It diffuses with the synaptic cleft that is located on the motor end plate of the nervous system.

c). The membrane potential is also known as the membrane voltage or the transmembrane potential. When it recaches the threshold, the voltage-gated Na channels opens to spread the action potential across sarcolemma.

d). The sodium ions in case of acetylcholine binding moves to the muscle fiber due to which the membrane potential rises.