MEDICAL PHYSIOLOGY

Detailed explanation-1: -During the process of accommodation the parasympathetic neurons of the Edinger–Westphal nucleus govern the contraction of the ciliary muscle (diminishing the distance a–b shown in Fig. 12.5), which relaxes some of the tension on the ligament, modifying the shape of the lens.

Detailed explanation-2: -Autonomic control of accommodation is predominantly parasympathetic and mediated by the action of acetylcholine on muscarinic receptors [19]. Parasympathetic input to the ciliary muscle mediates positive accommodation and meets the need for rapid focusing changes because of its fast onset of action (1-2 s).

Detailed explanation-3: -The regulation of pupil size and lens curvature involves the autonomic nervous system. Stimulation of the cranial parasympathetic system results in the constriction of the pupil and increased lens curvature, while stimulation of the spinal sympathetic system results in the dilation of the pupil.

Detailed explanation-4: -The ciliary muscles are responsible for the lens accommodation response.

Detailed explanation-5: -Ciliary ganglion neurons project to the ciliary body and the sphincter pupillae muscle of the iris to control ocular accommodation and pupil constriction, respectively.