Final answer:
Nicotine does stimulate and then block several nicotinic sub-types of cholinergic receptors, as it initially activates these receptors just like acetylcholine and can subsequently lead to their desensitization with continuous exposure.
Step-by-step explanation:
The statement that nicotine acts in the brain to first stimulate and then block several nicotinic sub-types of cholinergic receptors is true.
Nicotine binds to the nicotinic receptor, which is a ligand-gated ion channel, activating it in a way similar to acetylcholine.
Initially, this action stimulates the receptors on ganglionic neurons within both the sympathetic and parasympathetic systems, causing depolarization and excitation of the neurons.
With prolonged exposure to nicotine, however, desensitization of these receptors can occur, leading to a blocking or inhibitory effect.
Nicotine acts on the nicotinic sub-types of cholinergic receptors in the brain. Initially, it stimulates these receptors and then blocks them.
The nicotinic receptor is a ligand-gated ion channel in the cholinergic system, and when nicotine binds to it, it activates the receptor and causes depolarization. However, over time, nicotine can desensitize and ultimately block these receptors.