Chapter contents Overview Somatic motor component Origin, central course Intracranial course Final innervation Visceral motor component Origin and course Final innervation

Cranial Nerve III - Oculomotor Nerve Page 14 of 16 Action of the ciliary muscle - visceral motor component The lens of the eye is attached to the ciliary muscle by the suspensory ligaments. With the ciliary muscle at rest, a certain amount of tension is maintained on the suspensory ligaments keeping the lens relatively flat (low refractive power). When the ciliary muscle is stimulated to contract the distance from point "A" to point "B" in figure 3-14 is shortened, thus releasing some of the tension on the suspensory ligaments. With a decrease in tension on the suspensory ligaments the natural elasticity of the lens causes the curvature (and therefore the refractive power) of the lens to increase. Constriction of the pupil is mediated by the constrictor pupillae muscle. Figure 3-14. Action of the ciliary muscle.

Last revised: March 22, 1998