Final answer:
Succinylcholine is a direct-acting drug that inactivates acetylcholinesterase, leading to the accumulation of acetylcholine and causing muscarinic and nicotinic effects. It inhibits the release of acetylcholine, resulting in paralysis. Another drug called d-tubocurarine blocks the action of acetylcholine, causing muscle relaxation and paralysis.
Step-by-step explanation:
Succinylcholine is a direct-acting drug that inactivates the enzyme acetylcholinesterase, which prevents the breakdown of the neurotransmitter acetylcholine in the synapses. This action leads to both muscarinic and nicotinic effects. At the cholinergic synapse, acetylcholine is released and binds to either muscarinic or nicotinic receptors. Succinylcholine inhibits the release of acetylcholine from neurons, resulting in flaccid paralysis.
Another drug called d-tubocurarine also affects acetylcholine at the neuromuscular junction. It competitively blocks the action of acetylcholine by applying it directly to the end-plate of a muscle fiber. This causes the muscle cell to become insensitive to motor-nerve impulses and applied acetylcholine, leading to muscle relaxation and paralysis.
Atropine is an anticholinergic drug used to manage the symptoms of nerve agent poisoning. It acts as an antagonist to muscarinic acetylcholine receptors, blocking the effects of excess acetylcholine.