Question

Q16. What substances are released from sympathetic and parasympathetic fibres? Q17. Which drugs act on the same receptor or compete for the same receptor?

Answer 1

Ans) 16)Nerve fibers that release acetylcholine are referred to as cholinergic fibers. These include all preganglionic fibers of the ANS, both sympathetic and parasympathetic systems; all postganglionic fibers of the parasympathetic system; and sympathetic postganglionic fibers innervating sweat glands.

- By contrast, postganglionic fibers in the parasympathetic division are cholinergic and use acetylcholine as a neurotransmitter. In the sympathetic nervous system, the postganglionic neurons of sweat glands release acetylcholine for the activation of muscarinic receptors.

17)Agonists and antagonists:

- Agonists activate receptors to produce the desired response. Many hormones, neurotransmitters (eg, acetylcholine, histamine, norepinephrine), and drugs (eg, morphine, phenylephrine, isoproterenol, benzodiazepines, barbiturates) act as agonists. Antagonists prevent receptor activation.

- Antagonists mimic ligands that bind to a receptor and prevent receptor activation by a natural ligand. Preventing activation may have many effects. If a natural agonist binding to a receptor leads to an increase in cellular function, an antagonist that binds and blocks this receptor decreases the function.