Final answer:
Adrenergics and cholinergics are contraindicated with GI obstruction because adrenergic drugs can cause sphincter contraction that exacerbates the obstruction, and cholinergic drugs can increase motility which can lead to complications if the obstruction prevents normal passage.
Step-by-step explanation:
The student's question pertains to why adrenergics and cholinergics are contraindicated in cases of gastrointestinal (GI) obstruction. Adrenergics, also known as sympathomimetic drugs, mimic the actions of adrenergic molecules like norepinephrine and epinephrine, stimulating target organs just as the sympathetic nervous system would. They often cause contraction of sphincters in the digestive tract, which could exacerbate a GI obstruction by further limiting the propulsion of digestive contents.
Cholinergics act on the parasympathetic nervous system and are broken down into muscarinic agonists or antagonists, with the agonists increasing GI secretion and motility. In the context of a GI obstruction, stimulating motility could lead to increased pressure and possible complications if the obstruction prevents normal passage of digestive contents. Therefore, both adrenergic and cholinergic drugs can create harmful effects in the presence of a GI obstruction due to their actions on the alimentary canal's muscle contractions and secretions.