Answer:
B. 5, 1, 4, 3, 6, 2
Explanation:
Acetylcholine (ACh) is a molecule that functions as a neurotransmitter and plays diverse roles in brain and muscle function. Ach is released by the presynaptic neurons into the synaptic cleft. The nicotinic acetylcholine receptors are ACh ligand-gated ion channels located at the postsynaptic membrane which admit both sodium (Na+) and potassium (K+) ions. These receptors bind ACh, increasing the permeability of the postsynaptic membrane to Na+ and K+ ions. In consequence, ion channels open and sodium (Na+) ions enter the postsynaptic cell, causing the postsynaptic membrane to depolarize. An enzyme known as acetylcholinesterase breaks down acetylcholine into acetate and choline. If depolarization passes a threshold potential, an action potential is generated in the postsynaptic membrane. The generation of a postsynaptic potential at the excitatory synapse is known as excitatory postsynaptic potential. Once depolarization is complete, Na+ channels close and membrane permeability to Na+ ions declines to the resting levels.
