PSL300H1 Lecture Notes - Lecture 10: Melanin, Rhodopsin

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raspberrycamel287

13 Dec 2011

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Visual system takes up a lot of space in the brain. Images are turned backwards and upside down on retina. Camera model pupil as aperture, lens, retina as film. Pin-hole pupil entire depth of field perfectly focused on retina for all objects in the field (whether far or near: one ray of light from every direction enters the eyeball. Dilate pupil require lens to refocus divergent beam of light. October 01, 2007: no hindrance to incoming light be other neurons, maximal visual acuity can detect fine detail. Blood vessels and axons enter/exit retina via blind spot . Pit in retina region of highest visual acuity small photoreceptors (cones) packed in high density blood vessels and axons encircle this area they do not cross it. No light membrane depolarized (-40 mv: cgmp is abundant in dark conditions and opens cgmp-gated na+ channels. 10 eyeball and retina o vesicles released constantly.

Related Questions

The ciliary muscles in a horse's eye can make only small changes tothe shape of the lens, so a horse can't change the shape of thelens to focus on objects at different distances as humans do.Instead, a horse relies on the fact that its eyes aren't spherical.As the figure shows, different points at the back of the eye are atsomewhat different distances from the front of the eye. We say thatthe eye has a "ramped retina"; images that form on the top of theretina are farther from the cornea and lens than those that form atlower positions. The horse uses this ramped retina to focus onobjects at different distances, tipping its head so that light froman object forms an image at a vertical location on the retina thatis at the correct distance for sharp focus.

Part A
In a horse's eye, the image of a close object will be infocus
A. at the top of the retina.
B. at the bottom of the retina.

Part B
In a horse's eye, the image of a distant object will be infocus
A. at the top of the retina.
B. at the bottom of the retina.

Part C
A horse is looking straight ahead at a person who is standing quiteclose. The image of the person spans much of the vertical extent ofthe retina. What can we say about the image on the retina?
A. The person's head and feet are both in focus.
B. The person's feet are in focus; the head is out of focus.
C. The person's head is in focus; the feet are out of focus.
D. The person's head and feet are both out of focus.

Part D
Certain medical conditions can change the shape of a horse'seyeball; these changes can affect vision. If the lens and corneaare not changed but all of the distances in the figure areincreased slightly, then the horse will be
A. unable to focus clearly at any distance.
B. nearsighted.
C. farsighted.

The figure (a) shows the basicstructure of a human eye. Light refracts into the eye through thecornea and is then further redirected by a lens whose shape (andthus its ability to focus the light) is controlled by muscles. Wecan treat the cornea and eye lens as a single effective thin lens(figure (b)). A "normal" eye can focus parallel light rays from adistant object O to a point on the retina at the back of the eye,where processing of the visual information begins. As an object isbrought close to the eye, however, the muscles must change theshape of the lens so that rays from an inverted real image on theretina (figure (c)). Suppose that for the parallel rays of figures(a) and (b), the focal length of the effective thin lens of the eyeis 2.7 cm. For an object at a distance p = 26.0 cm, what focallength f' of the effective lens is required for it to be seenclearly?

The figure (a) shows the basicstructure of a human eye. Light refracts into the eye through thecornea and is then further redirected by a lens whose shape (andthus its ability to focus the light) is controlled by muscles. Wecan treat the cornea and eye lens as a single effective thin lens(figure (b)). A "normal" eye can focus parallel light rays from adistant object O to a point on the retina at the back of the eye,where processing of the visual information begins. As an object isbrought close to the eye, however, the muscles must change theshape of the lens so that rays from an inverted real image on theretina (figure (c)). Suppose that for the parallel rays of figures(a) and (b), the focal length of the effective thin lens of the eyeis 2.5 cm. For an object at a distance p = 20.0 cm, what focallength f' of the effective lens is required for it to be seenclearly?

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PSL300H1 Lecture Notes - Lecture 10: Melanin, Rhodopsin

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