BGYB30H3 Lecture 14 Notes Autonomic and Somatic Control-Oct 27

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BGYB30H3 Lecture 14 Notes
-cornea is the area of the eye where light enters, and the pupil can change amount of light
entering
-lens focuses light onto the retina, which contains photoreceptor cells
-fovea has the highest visual acuity
-optic disk (blindspot) is found at the back of the retina and contains no photoreceptors
-zonules and cilary control the shape of the lens
-aqueous humour supports the lens while the vitreous humour controls the shape of the eye
ball
-neural pathways from the eye go to the optic chiasm where it may crossover and synapse in
the lateral geniculate nucleus of the thalamus
-collaterals from thalamus to the midbrain synapse onto cranial nerve III to control pupil
diameter
-lens flip image to focus on the retina and changes shape through accommodation
-light rays refract in the fluid of the eye to produce an inverted image on the retina
-distance from centre of the lens to the focal point on the retina is the focal length
-presbyopia is the loss of the ability of the lens to change shape and occurs with aging
-when light is not bent, cilary muscles are relaxed and zonules contract
-when light is bent, cillary muscles contract and zonules relax
-distant objects of 20 meters or more causes the lens to be flat because light rays are parallel
-when object is closer than 20 meters, the lens becomes more convex to converge the image on
the retina
-rounding of the lens shortens focal length
-common visual defects occur because the eyeball is too long or short or the cornea is abnormal
in its curvature
-hyperopia is farsightedness in which the image is behind the retina (convex lens is needed)
-myopia is nearsightedness in which the image is in front of the retina (concave lens is
needed)
-ganglion cells converge onto the optic nerve (cranial nerve 2)
-photoreceptors are found at the back of the retina
-light hits the photoreceptors in the fovea directly
-outer segment of photoreceptors contains light sensitive visual pigment
-outer fibre of photoreceptor contains synaptic terminals that release glutamate onto bipolar
cells
-rods are the most numerous and have the visual pigment rhodopsin that functions well in low
light
-cones are only found in the fovea and detect colour/daylight vision
-rhodopsin contains opsin and retinal
-in response to darkness, opsin and retinal bind to inactivate rhodopsin
-retinal is activated by light
-sodium influxes into the photoreceptor while potassium effluxes out of the photoreceptor in
the absence of light
-sodium influx is greater, causing the resting membrane potential to be depolarized
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Document Summary

Cornea is the area of the eye where light enters, and the pupil can change amount of light entering. Lens focuses light onto the retina, which contains photoreceptor cells. Optic disk (blindspot) is found at the back of the retina and contains no photoreceptors. Zonules and cilary control the shape of the lens. Aqueous humour supports the lens while the vitreous humour controls the shape of the eye ball. Neural pathways from the eye go to the optic chiasm where it may crossover and synapse in the lateral geniculate nucleus of the thalamus. Collaterals from thalamus to the midbrain synapse onto cranial nerve iii to control pupil diameter. Lens flip image to focus on the retina and changes shape through accommodation. Light rays refract in the fluid of the eye to produce an inverted image on the retina. Distance from centre of the lens to the focal point on the retina is the focal length.

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