Psychology 2115A/B Lecture Notes - Lecture 2: Retinal Pigment Epithelium, Ciliary Muscle, Table Tennis

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Chapter 2: Beginnings of Perception/ The Eye
May 19, 2016
Part 1:
Light is the Stimulus for Vision
Electromagnetic energy creates a spectrum described as wavelengths (how
long a wave is)
Humans can only detect the visible light (only humans, some animals can see
into the infrared or ultraviolet)
Depending on the detectors that the animal/human has
We can have things that can detect the light, but we have to convert into
energy that we can visually process (ex: TV, radars, radio)
We can see 400-700 nanometers of the visual spectrum (humans)
Most perceived light is reflected light (ex: looking straight at a
lamp/projector light)
oPhotons of light being blasted onto surfaces, sometimes it is
consumed by the surface and the rest is transmitted to your eye
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Focusing Images on the Retina
Cornea=protect the eye and focus light (focus 60-80% of light), no muscles
attached, doesn’t change/move (aka: fixed objects like a magnify glass)
Aqueous Humor= very thin body layer behind the cornea
Vitreous Humor=thick fluid holding the shape of the eye (structure looks
like a ping pong ball with a thumb indent at the front where the lens will
sit)
Iris=coloured part of the eye
oCircular muscles=relaxed/contracted
oRadial muscles=contracted/relaxed
oTo make the pupil bigger or smaller to pull the pupil open/closed to
allow more/less light into the eye
oWhen radial muscles are contracted, it makes the pupil bigger to let
light in
oWhen circular muscles are contracted, it makes the pupil smaller to
keep light out
Pupil= black spot in the centre of the eye and helps to focus light by getting
the light on the proper part of the lens
oSmall apertures help to focus light to some degree
Lens=adjusts shape from moment to moment, to help bring them into focus
oWhen looking at an object far away, the light coming in is parallel
oWhen looking at a close object, the light bouncing off is scattering and
diffusing, but the further you get away, the light coming is lesser but
more parallel
oIf light is coming in parallel, then we want it to focus in a cone shape
oCiliary body/muscles=like a donut that goes all the way around the
lens
When contracted, they pull toward and forward
Zonules (aka: suspensory ligaments)=thread-like ligaments
When looking at something closer, the muscles come together
and zonules go slack
Focusing apparatus (cornea, pupil, lens) causes the image to flip in the eye
oLight passing through all the structures
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An image of the cup is focused on the retina, which lines the back of the eye.
The close up of the retina on the right shows the receptors and other neurons
that make up the retina
oTwo main receptor cells= rods and cons
oFloaters are cellular debris that gets stuck between the retina and the
fovea
oWe need the pigment epithelium to recharge before
Focusing light rays by the eye
oA. Rays of light coming form the small light source that is further than
20 feet away are approx. parallel. The focus point for parallel light is
at A on retina
oB. Moving an object closer to the relaxed eye pushes the focus point
back. Here, the focus point is at B, but light is stopped by the back of
the eye
oC. Accommodation of the eye (indicated fatter lens) increases the
focusing power of the lens and brings the focus point for a near object
back to A on the retina (ex: 3D movies)
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