Human Physiology, 14th edition (2016)

The Autonomic Nervous System 259

Table 9.7 | Adrenergic and Cholinergic Effects of Sympathetic and Parasympathetic Nerves

Effect of

Sympathetic Parasympathetic

Organ Action Receptor * Action Receptor *

Eye

Iris

Radial muscle Contracts (dilates pupil) a 1 — —

Circular muscle — — Contracts (constricts pupil) M

Heart

Sinoatrial node Increases heart rate b 1 Decreases heart rate M

Contractility Increases b 1 Decreases (atria) M

Vascular Smooth Muscle

Skin, splanchnic vessels Contracts (vasoconstriction) a , b — —

Skeletal muscle vessels Relaxes (vasodilation) b 2 — —

Relaxes (vasodilation) M ** — —

Bronchiolar Smooth Muscle Relaxes (bronchodilation) b 2 Contracts (bronchoconstriction) M

Gastrointestinal Tract

Smooth muscle

Walls Relaxes b 2 Contracts M

Sphincters Constricts a 1 Relaxes M

Secretion Inhibits a 2 Stimulates M

Myenteric plexus Inhibits a — —

Genitourinary Smooth Muscle

Bladder wall (detrussor m.) Relaxes slightly b 2 Contracts M

Urethral sphincter Contracts a 1 Relaxes M

Uterus, pregnant Relaxes b 2 — —

Contracts a 1 — —

Penis Ejaculation a 1 Erection M

Skin

Pilomotor smooth muscle Contracts a 1 — —

Sweat glands

Thermoregulatory Increases M — —

Apocrine (stress) in palms Increases a 1 — —

*Adrenergic receptors are indicated as alpha ( a ) or beta ( b ); cholinergic receptors are indicated as muscarinic (M).
**Vascular smooth muscle in skeletal muscle has sympathetic cholinergic dilator fibers.
Source: Reproduced and modified, with permission, from Katzung, B.G.: Basic and Clinical Pharmacology, 6th edition, copyright Appleton & Lange, Norwalk, CT,
1995, with modifications from Goodman & Gilman’s The Pharmalogical Basis of Therapeutics, Eleventh edition, 2006, McGraw-Hill.