Download Wavelengths of Light not Absorbed by an Object are Reflected to Our Eyes | BMS 360 and more Study notes Biology in PDF only on Docsity! 3 February Wavelengths of light not absorbed by an object are reflected to our eyes Figure 7.22 White portion of eye – sclera Tough connective tissue Rectus muscles attached to sclera Cornea Transparent, light gets through Break in sclera Anterior chamber of eye Contains aqueous humor Between cornea and lens Lens Made of elastic protein material Strings (zonular fibers) connect lens to ciliary muscle Muscle pulls – lens flattens Muscle relaxes – lens becomes rounded Posterior chamber Contains vitreous humor Choroid in back of eye Picks up stray light → sharper vision Retina In front of choroid Contains photoreceptors (sensitive to light) In some diseases, blood vessels in eye proliferate, blocking flow of light → blindness Light → surface of cornea → bent (refracted) → again on hitting surface of lens Lens elasticity changes angle light is refracted Light focused on back of eye in fovea centralis Optic disk No photoreceptors Entrance of optic nerve Blind spot Figure 7.26 Astigmatism – deformation in cornea or lens Light is not focused where it should be Near sighted Eyeball too long Myopia Image focused in front of the retina Corrective lens (concave) changes angle of light Far sighted Eyeball too short Hyperopia Image focused behind the retina Corrective lens (convex) changes angle of light Glaucoma Excessive pressure from fluid Vitamin A deficiency – night blindness Cones 7 million Concentrated at fovea centralis Photopsin Blue, red, and green sensitive cones Color vision Visual acuity Requires bright light Figure 7.30 We can only see 0.1% of the entire electromagnetic spectrum Light changes conformation of opsins Figure 7.28 In cones → in disks No light Molecule converts GTP → cGMP Gates Na+/Ca2+ channel Channel opens → depolarization “Dark current” Light Opsin converted Activates transduction > activates phosphodiesterase
cGMP destroyed
Channels close
Hyperpolarization
