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Accommodation

Homeostasis and response · The human nervous system · note 6 of 8

Spec 4.5.2.3Triple onlyDownload these notes (PDF)9 pages

AccommodationSpec 4.5.2.3

Accommodation
The process of changing the shape of the lens to focus on near or distant objects.
Focusing on near and distant objects
Near objectDistant object
Ciliary musclesContractRelax
Suspensory ligamentsLoosenPulled tight
Lens shapeThickerPulled thin
Refraction of light raysStronglyOnly slightly
Two lens diagrams: for a near object the ciliary muscles contract, the suspensory ligaments loosen and the lens is thicker; for a distant object the ciliary muscles relax, the suspensory ligaments are pulled tight and the lens is pulled thin. In both, light rays focus on the retina.Tap to enlarge
Accommodation. Near object: muscles contract, ligaments loosen, lens thicker. Distant object: muscles relax, ligaments tight, lens thin.