Parasympathetic denervation (which normally occurs in the course of a Bell palsy) does not affect either the size of the pupil or the amplitude of accommodation. Without parasympathetic innervation, the iris sphincter constricts and the ciliary muscles relax. The ciliary body shrinks, the lens becomes more convex, and the iris dilates, providing no more than 20/20 vision. A pupil that has been denervated remains fixed in size as a result of muscular tension and lack of parasympathetic innervation. Parasympathetic denervation occurs in sympathetic ophthalmia and occurs in some cases of sympathetic ophthalmia following enucleation.
About one-third of all parasympathetic innervation of the eye comes from the Edinger-Westphal nucleus in the brainstem, the remainder comes from the superior salivatory nucleus in the pons, most of which is in the rostral two-thirds of the nucleus. The Edinger-Westphal nucleus sends preganglionic cholinergic fibers to the ciliary ganglion, which in turn sends postganglionic parasympathetic nerve fibers to the ciliary body, iris, and retina. The superior salivatory nucleus also sends preganglionic cholinergic fibers to the ciliary ganglion, which in turn sends postganglionic parasympathetic nerve fibers to the ciliary body, iris, and retina.
For required software patching, Amazon RDS automatically applies the patches to your DB instance via a snapshot, and issues a rolling restart. This is done in the background by Amazon RDS so your instance will not be unavailable while the patching occurs.
The frequency of the required database engine patches is determined by your workload. You can view the details of the required database engine patches for your DB instance by using the DescribeCurrentEnginePatches operation.
Database engine patches consist of a collection of tasks that are applied to a DB instance to improve the performance of a given workload. At a minimum, these tasks include:
add, remove, or modify tablespaces, and
However, if a major patch is required for your database engine version, your instance will need to be monitored in order to prevent problems with the service causing your instance to stop or fail.
Parasympathetic signals that originate in the Edinger-Westphal nucleus are carried by cranial nerve III (the oculomotor nerve) and travel through the ciliary ganglion via the postganglionic parasympathetic fibers which travel in the short ciliary nerves and supply the ciliary body and iris. Parasympathetic activation of the M3 muscarinic receptors causes ciliary muscle contraction. The effect of contraction is to decrease the diameter of the ring of ciliary muscle causing relaxation of the zonule fibers, the lens becomes more spherical, increasing its power to refract light for near vision.
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