Final answer:
Neostigmine is the medication that the nurse should administer in a cholinergic crisis with myasthenia gravis.
Step-by-step explanation:
In a cholinergic crisis with myasthenia gravis, the nurse should administer Neostigmine as the medication of choice. Myasthenia gravis is an autoimmune disorder characterized by muscle weakness caused by a blockage of nicotinic acetylcholine receptors. Neostigmine is a cholinesterase inhibitor that increases the availability of acetylcholine at the neuromuscular junction, improving muscle strength and function in patients with myasthenia gravis.