Passage
Saliva, a secreted fluid with multiple physiologic functions, is composed of water (~99%) , proteins, and electrolytes. Together, these components facilitate nutrient consumption, respiration, and communication. For example, saliva aids in digestion by serving as a lubricant during mastication and by initiating carbohydrate and fat metabolism. In addition, the calcium and phosphate present in saliva promote tooth remineralization, and antimicrobial and chemical buffering agents give saliva protective properties.The gustatory-salivary reflex, the secretion of saliva from the salivary glands in response to gustation (taste) , is primarily mediated by the parasympathetic division of the nervous system. In general, parasympathetic pathways originate from the brain stem or the sacral spinal cord. Fibers originating from nuclei in these regions synapse onto ganglia that lie in close proximity to the target organ. Both preganglionic neurons (those originating from the nuclei) and postganglionic neurons (those originating from the ganglia) release acetylcholine (ACh) .In the gustatory-salivary reflex, activation of taste receptors in the tongue sends impulses to the superior and inferior salivatory nuclei in the brainstem. Local processing within these nuclei activates the parasympathetic pathways that innervate the salivary glands. Ultimately, ACh released from postganglionic neurons acts on the muscarinic acetylcholine receptors (mAChRs) on the secretory cells of the salivary gland to stimulate salivation (Figure 1) .
Figure 1 Parasympathetic regulation of salivary secretionSympathetic stimulation of the salivary glands also promotes salivation but to a lesser degree than parasympathetic stimulation. This may contribute to what is often perceived to be decreased salivation when the sympathetic division is more active than its counterpart. Unlike parasympathetic pathways, sympathetic pathways originate in the thoracic and lumbar spinal segments, and the ganglia lie in close proximity to the spinal cord. Although preganglionic neurons of the sympathetic nervous system release ACh, the postganglionic neurons often release norepinephrine.
-The drug cevimeline hydrochloride is a cholinergic agonist. Administration of cevimeline hydrochloride would be expected to cause:

Question

Passage
Saliva, a secreted fluid with multiple physiologic functions, is composed of water (~99%) , proteins, and electrolytes. Together, these components facilitate nutrient consumption, respiration, and communication. For example, saliva aids in digestion by serving as a lubricant during mastication and by initiating carbohydrate and fat metabolism. In addition, the calcium and phosphate present in saliva promote tooth remineralization, and antimicrobial and chemical buffering agents give saliva protective properties.The gustatory-salivary reflex, the secretion of saliva from the salivary glands in response to gustation (taste) , is primarily mediated by the parasympathetic division of the nervous system. In general, parasympathetic pathways originate from the brain stem or the sacral spinal cord. Fibers originating from nuclei in these regions synapse onto ganglia that lie in close proximity to the target organ. Both preganglionic neurons (those originating from the nuclei) and postganglionic neurons (those originating from the ganglia) release acetylcholine (ACh) .In the gustatory-salivary reflex, activation of taste receptors in the tongue sends impulses to the superior and inferior salivatory nuclei in the brainstem. Local processing within these nuclei activates the parasympathetic pathways that innervate the salivary glands. Ultimately, ACh released from postganglionic neurons acts on the muscarinic acetylcholine receptors (mAChRs) on the secretory cells of the salivary gland to stimulate salivation (Figure 1) .

Figure 1 Parasympathetic regulation of salivary secretionSympathetic stimulation of the salivary glands also promotes salivation but to a lesser degree than parasympathetic stimulation. This may contribute to what is often perceived to be decreased salivation when the sympathetic division is more active than its counterpart. Unlike parasympathetic pathways, sympathetic pathways originate in the thoracic and lumbar spinal segments, and the ganglia lie in close proximity to the spinal cord. Although preganglionic neurons of the sympathetic nervous system release ACh, the postganglionic neurons often release norepinephrine.
-The drug cevimeline hydrochloride is a cholinergic agonist. Administration of cevimeline hydrochloride would be expected to cause:

Quizplus · Accepted Answer

11ecba2d_0fe9_3952_a3bf_61f207831ad0_MD0008_00 Membrane-bound receptors respond to ligands that are either endogenous (originating from the organism) or exogenous (foreign to the organism). Agonists are ligands that activate the receptor and promote its downstream effects. In contrast, antagonists are ligands that deactivate or inhibit the receptor, preventing its downstream effects. According to the passage, parasympathetic pathways utilize acetylcholine (ACh) for signaling between the pre- and postganglionic neurons, as well as for signaling between the postganglionic neuron and the target tissue (eg, salivary gland). Because the gustatory-salivary reflex arc is primarily mediated by parasympathetic pathways, it must exert its effects (stimulation of salivation) through cholinergic signaling. The question states that cevimeline hydrochloride is a cholinergic agonist (ie, a ligand that activates ACh receptors). Treatment with a drug that activates ACh receptors would be expected to increase salivation by activating the muscarinic acetylcholine receptors (mAChRs) present on secretory cells of the salivary gland. (Choices B and D) Cevimeline hydrochloride is an agonist that activates mAChRs to stimulate salivation; it does not inhibit mAChRs. (Choice C) Stimulation of mAChRs would lead to increased, not decreased, salivation. Inhibition of mAChRs by an antagonist would lead to decreased salivation. Educational objective: Agonists are ligands that activate the receptors they interact with and induce downstream effects. Antagonists are ligands that inhibit the receptors they interact with and block downstream effects.

Passage Saliva, a Secreted Fluid with Multiple Physiologic Functions, Is Composed