Sight (Vision)

Question 1

Conjunctiva

Answer 1

thin layer of cells that line the inside of your eyelids from the eye

Question 2

Sclera

Answer 2

usually absorbs by the time light gets to it; the whites of the eye; thick fibrous tissue that covers posterior 5/6 of the eye; attachment point for muscles; extra layer of protection and structure of eyeball; covered by conjunctiva

Question 3

Cornea

Answer 3

thick sheet of fibrous tissue that makes up the anterior 1/6 of the eye; starts to bend light as this is the first structure that light hits

Question 4

Anterior Chamber

Answer 4

filled with aqueous humor, which provides pressure to maintain the shape of the eyeball; allows nutrients and minerals to supply the cells of the cornea and iris

Question 5

Pupil

Answer 5

the opening in the middle of the iris; the size of the pupil can get bigger/smaller depending on the iris relaxing/contracting, respectively; the pupil modulates the amount of light that can enter the eye

Question 6

Iris

Answer 6

gives the eye its color; it is the muscle that relaxes/constricts to change the size of the pupil

Question 7

Lens

Answer 7

bends the light as it goes to the back of the eyeball; focuses light specifically on the fovea of the retina; adjust how much it bends light by changing its shape dictated by the suspensory ligaments

Question 8

Suspensory Ligaments

Answer 8

attached to the ciliary muscle; the combination of the suspensory ligaments and the ciliary muscle yield the ciliary body, which secretes the aqueous humor

Question 9

Posterior Chamber

Answer 9

area behind the iris to the back of the lens; also filled with aqueous humor

Question 10

Vitreous Chamber

Answer 10

filled with vitreous humor, which is a jelly-like substance providing pressure to maintain shape of the eyeball and nutrients to the inside of the eyeball

Question 11

Retina

Answer 11

inside, back area of the eyeball filled with photoreceptors where the ray of light is converted from a physical waveform to an electrochemical impulse that the brain can interpret

Question 12

Macula and Fovea

Answer 12

• macula = special area of the retina that has a larger concentration of cones and smaller concentration of rods
• fovea = area of the retina completely concentrated with cones (rest of retina mostly concentrated with rods)

Question 13

Rods

Answer 13

• photoreceptor cells specializing in night vision; about 120 million present
• 1000x more sensitive to light than cones and tell us whether or not light is present
• slow recovery time - takes a while to adjust to the dark; need to be reactivated
• found primarily at the periphery, where light has to travel across a bundle of axons and therefore loses some energy; less light gets to rods

Question 14

Cones

Answer 14

• photoreceptor cells specialized in recognizing color (60% red, 30% green, and 10% blue); about 6-7 million present
• almost all the cones are found at the fovea
• fast recovery time; adapt to change quickly (fire more frequently)
• at fovea, there are no axons blocking the cones and therefore, the light hits the cones directly resulting in higher resolution

Question 15

Choroid

Answer 15

pigmented black in humans and therefore absorbs all light; is a network of blood vessels that help nourish the retina; some animals have a different colored choroid giving them better night vision

Question 16

Transmission and Transduction

Answer 16

• Transmission = electrical activation of one neuron by another neuron
• Transduction = energy is transformed from one form to another (in this case light energy –> electrical energy)

Question 17

Perception and Sensation

Answer 17

• Perception = conscious sensory experience of neural processing (neural transformation of multiple neural signals into perception)
• Sensation = physical stimulus converted to neural impulse

Question 18

Light

Answer 18

EM wave ranging from from gamma rays to radio waves with visible light in the middle spanning from 400 to 700 nm

Question 19

The Phototransduction Cascade (PTC)

Answer 19

process of making light –> neural impulse by turning off rods and cones (outline process of rod but also applies to cone - photopsin in cones)

1. Rod hyperpolarizes turning OFF
2. When rod is OFF, the ON CENTER bipolar cell is turned on, which activates the ON CENTER retinal ganglion cell, which sends signal to optic nerve to brain
   - When rod is depolarized, it’s ON; this turns off the ON CENTER bipolar cell and activates the OFF CENTER bipolar cell, which activates the OFF CENTER retinal ganglion cell, which sends signal to optic nerve to brain

Question 20

Rod Hyperpolarizes upon Light Exposure

Answer 20

1. Optic discs within rod contain protein rhodopsin, which has the molecule retinal. Retinal changes from bent to straight form upon being exposed to light, which ultimately changes the shape of rhodopsin
2. With the change in rhodopsin, transducin (composed of alpha, beta, and gamma subunits) breaks from rhodopsin and the alpha subunit binds to phosphodiesterase
3. PDE converts cGMP, which was responsible for keeping the Na+ channels open to depolarize the cell, to GMP
4. The Na+ channels close and the cell hyperpolarizes and thus turns OFF

Question 21

Photopic, Mesopic, Scotopic Vision

Answer 21

• Photopic Vision = occurs at high light levels
• Mesopic Vision = occurs at dawn/dusk, involving both rods and cones
• Scotopic Vision = occurs at low light levels

Question 22

Blind Spot

Answer 22

place where optic nerve connects with the retina; area has no rods or cones

Question 23

Right Visual Field Goes to Left Side of Brain

Answer 23

ray of light from the right visual field hits the nasal side of the right eye and the temporal side of the left eye

Question 24

Left Visual Field Goes to Right Side of Brain

Answer 24

ray of light from the left visual field hits the nasal side of the left eye and the temporal side of the right eye

Question 25

Optic Chiasm

Answer 25

convergence point of the optic nerves of each eye

• all light from the nasal side of each eye crosses the optic chiasm to the other side (right eye nasal side crosses to left side of brain)
• light from the temporal side of each eye does NOT cross the optic chiasm

Question 26

Feature Detection

Answer 26

when looking at an object, you need to break it down into its component features to make sense of what you’re looking at; consider the color, form, and motion

Question 27

Trichromatic Theory (Color)

Answer 27

dictated by the cones (see cones flashcard)

-object reflects red –> red light hits the red cone –> fires action potential –> brain detects RED

Question 28

Parvocellular Pathway (Form and Color)

Answer 28

good at spatial resolution (boundaries and shape - high level of form/details) and color; poor temporal res.
-dictated by the cones

Question 29

Magnocellular Pathway (Motion)

Answer 29

good at temporal resolution (motion); poor spatial res.

-dictated by the rods

Question 30

Parallel Processing

Answer 30

detect/focus all information (color, form, motion) at one time