Question

Parasympathetic nerves

A. Have opposite effects to sympathetic nerves on intestinal smooth muscle.

B. Have opposite effects to sympathetic nerves on iris smooth muscle.

C. Cause vasodilatation in skeletal muscle during prolonged exercise.

D. Cause sweat secretion in skin when body temperature rises.

E. Have longer postganglionic than preganglionic fibres.

Answer 1

A. True Parasympathetic nerves stimulate, and sympathetic nerves inhibit, intestinal smooth muscle contractions.

B. False Both contract iris smooth muscle; however parasympathetics constrict the pupil by contracting circular muscle, sympathetics dilate it by contracting radial muscle.

C. False Skeletal muscle has no parasympathetic nerve supply; local metabolites are responsible for the vasodilatation.

D. False Skin has no parasympathetic innervation; sympathetic cholinergic nerves are responsible for the increase in sweating when body temperature rises.

E. False The reverse is the case.