A student waiting outside an examination hall notices her mouth is dry and her saliva feels thick and sticky. The autonomic division responsible for this character of salivary secretion acts through which receptor and produces what composition?

• A Sympathetic, beta-adrenergic, protein and enzyme-rich viscid saliva ✓
• B Parasympathetic, muscarinic, copious watery saliva
• C Sympathetic, alpha-2 adrenergic, reduced volume of watery saliva
• D Parasympathetic, nicotinic, mucin-rich saliva

Explanation

Sympathetic stimulation of salivary glands, mediated largely by beta adrenergic receptors coupled to cAMP, produces a small volume of viscid secretion rich in proteins and enzymes such as amylase, which is why stress gives thick sticky saliva rather than a dry gland. The glands are never fully shut off because they maintain a basal flow driven by parasympathetic tone, so option B describes the opposite situation.

Reference: Ganong Review of Medical Physiology, 26th ed.

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