Effects of the Parasympathetic and Sympathetic ANS  





Eye (iris)

Constricts pupils by stimulating sphincter pupillae muscles

Dilates pupils by stimulating dilator pupillae muscles

Eye (ciliary muscle)

Stimulates ciliary muscle to bulge the lens for close vision

Weakly inhibits muscle, which results in flattening of the lens for far vision

Glands (nasal, lacrimal, gastric, pancreas)

Stimulates secretory activity

Inhibits secretory activity;  constricts  blood vessels supplying the glands

Salivary glands

Stimulates secretion of watery saliva

Stimulates secretion of thick, viscous saliva

Sweat glands

No effect (no innervation)

Stimulates copious sweating (cholinergic fibers)

Adrenal medulla

No effect (no innervation)

Stimulates medulla cells to secrete epinephrine and norepinephrine

Arrector pili muscles attached to hair follicles

No effect (no innervation)

Stimulates contraction (erects hairs and produces "goosebumps")

Heart (muscle)

Decreases rate; slows heart

Increases rate and force of heartbeat

Heart (coronary blood vessels)

No effect (no innervation)

Causes vasodilation

Urinary bladder/urethra

Causes contraction of smooth muscle of bladder wall; relaxes urethral sphincter; promotes urination

Causes relaxation of smooth muscle of bladder wall; constricts urethral sphincter; inhibits urination


Constricts bronchioles

Dilates bronchioles

Digestive tract organs

Increases motility (peristalsis) and amount of secretion by digestive organs; relaxes sphincters to allow movement   of foodstuffs along tract

Decreases activity of glands and muscles of digestive system and constricts sphincters (e.g., anal sphincter)


Stimulates synthesis of glycogen and decrease of blood glucose


Stimulates breakdown of glycogen and increase of blood glucose



Excites (gallbladder contracts to expel bile)

Inhibits (gallbladder is relaxed)


No effect (no innervation)

Promotes renin release; causes vasoconstriction; decreases urine output


Causes erection (vasodilation)

Causes ejaculation


Causes erection (vasodilation) of clitoris; increases vaginal lubrication

Causes contraction of vagina

Blood vessels

Little or no effect

Constricts most blood vessels and increases blood pressure; constricts vessels of abdominal viscera and skin to divert blood to muscles, brain, and heart when necessary;  epinephrine dilates vessels of the skeletal muscles during exercise

Blood coagulation

No effect (no innervation)

Increases coagulation

Cellular metabolism

No effect (no innervation)

Increases metabolic rate

Adipose tissue

No effect (no innervation)

Stimulates lipolysis (fat breakdown)