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MCAT PSYCHOLOGY > Sight (Vision) > Flashcards

Sight (Vision) Flashcards

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1
Q

Describe the structure of the Sclera.

A
  1. Whites of the eye
    2) thick fibrous tissue
    3) Covers 5/6th of the eye
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2
Q

What are the 3 major purposes of the sclera?

A
  1. Extra layer of protection
  2. structure
  3. Attachment points for the muscles
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3
Q

Describe the Structure of the cornea.

A

1) transparent
2) thick layer of fibrous tissue
3) covers 1/6th of the eye (anterior)

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4
Q

What are the major purposes of the cornea?

A

1) First part of the eye the light hits
2) Starts to bend lights
3) Protects Eye

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5
Q

What is the cornea lined with?

A

Sclera

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6
Q

Thin layer of epithelial cells in front of cornea.

A

Describe the structure of the conjunctiva.

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7
Q

What is the purpose of the conjunctiva?

A

1) Protect the cornea from friction
2) Line the inner part of your eyelids from the eye
3) Helps Moisturizer/Lubricant Cornea

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8
Q

Describe Structure of the Anterior Chamber.

A

1) Located Behind the Cornea

2) Filled with aqueous humour

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9
Q

Describe the Lens.

A

1) Bicontact Lens (Curved on both sides)

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10
Q

What is aqueous humour and where is it located?

A

1) Located in the anterior chamber
2) Anterior Chamber of the eye consisting of water, salt, nutrient and minerals (supplies this to the cell’s cornea and iris)

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11
Q

What is the purpose of the aqueous humour in the Anterior Chamber?

A

1) Supply nutrients to cornea and iris

2) Provide pressure to help maintain shape of the eye

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12
Q

What is the purpose of the Lens?

A

1) Bend Light that goes to the back of the eye
2) Adjusts how much light bends by changing its shape (using suspensory ligaments)
3) Focus light on the fovea of the retina

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13
Q

What are the two important part of the Lens and what is their purpose?

A

1) Suspensory Ligaments attached to ciliary muscles form the ciliary body
2) Change the shape of the Lens (Makes the Lens thinner or thicker based on how far or close and object is)
3) Secretes aqueous humour

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14
Q

What is the structure of the iris?

A

1) Pigmented part of the eye

2) Consist of two muscles that expand and contract

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15
Q

What is the purpose of the iris?

A

To expand and contract to adjust how much light is enter that eye (changes he shape of the pupil)

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16
Q

What is the pupil and what is its purpose?

A

1) Opening of the iris
2) Gets bigger/smaller based on the iris relaxing/contracting respectively
3) controls amount of light entering the eye (controlled by the muscles of the iris

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17
Q

What is the vitreous humour?

A

1) Makes up the posterior chamber of the eye (behind the iris)
2) Jelly-like substance; Consists of the salt, water, proteins (mainly albumin)
3) Transparent

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18
Q

What is the purpose of the vitreous humour?

A

1) Suspend Lens in Place

2) Provides structure to the eye

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19
Q

Describe the structure of the retina.

A

1) Coats the enter back of the eyeball
2) Consists of the cells called photoreceptors
3) Tinted Red (causes red eyes in pictures - light of a camera bounces off the retina of the eye, causing red eye effected. Can be prevented by using a camera with a double flash. first flash makes the pupil smaller so when the second flash goes off, the pupil is so small not as much light can enter the eye to bounce off the retina)

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20
Q

What are photoreceptors in the retina?

A

1) Converts a ray of light from a physical waveform to an electrochemical impulse that can be interpreted by the brain.

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21
Q

What is the major purpose of the retina?

A

Sends fiber to the back of the eye, so the fibers can go to the brain (this forms the optic nerve)

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22
Q

What happens when the retina sends fibers through the optic nerve?

A

The fibers go to the brain to make sense of what you’re looking at.

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23
Q

Describe the structure of the choroid. Where is it located?

A

1) located in the retina
2) Pigmented Black
3) Network of blood vessels that help nourish the retina

24
Q

What is the purpose of the choroid?

A

It is Black, thus it absorbs all light (cats have colored choroids, which helps them see better at night. This happpens because since the choroid is lighter, the light will bounce off the choroid and hit the retina, which reabsorbs light and helps them see better in the dark)

25
Q

What is the fovea and what does it consist of? where is it located?

A

1) Located in the center of a macula (which is located on the retina)
2) Covered with cones
3) Fovea is the region of the eye important for color and detail due to the cones within it

26
Q

What is the purpose of cones? Where are they located?

A

1) Detect Color
2) Allows for detailed vision
3) Located on foveas (which are located on the macula on the retina of the eye)

27
Q

What are rods and what is their purpose?

A

Rod shaped light detectors located on the retina.

28
Q

What is sensation?

A

requires a physical stimulus to be converted to a neural impulse (by a receptor)

29
Q

What is light?

A

An electromagnetic wave part of an electromagnetic spectrum

30
Q

What is the EM spectrum and where does light fall in the spectrum?

A
  1. Consists of low wavelengths (gamma rays) to high wavelengths (AM/FM waves).
  2. Light lies in the middle
31
Q

What is the range of light on the EM spectrum

A

400 (violet) to 700 (red) (we get most of our light of the sun)

32
Q

What happens when light hits the eye?

A

1) Light enters pupil and goes to retina (which contains rods and cones) and “bounces off” the back of the eye
2) Hits the rods in the back of the eye (on the retina)
2) Phototransduction Cascade is triggered

33
Q

What are photoreceptors and what do they do?

A

1) Cones and rods
2) Specialized nerve that converts light into a neural impulse
3) Both cones and rods have the same internal structures

34
Q

What is the difference between rods and cones?

A

Rods

  • 120 millions; Rods are very sensitive to light (1000x more than cones), good for
  • Have rhodopsin
  • In the periphery of the eye
  • Slow recovery time (takes longer to fire another action potential, why it takes time for your eyes to adjust to darkness or a brightness)
  • DO NOT PRODUCE COLOR VISION (only responsible for detecting light = black/white vision)

Cones

  • 6-7 million cones; mostly important for color vision
  • Photopsin
  • In the Fovea (some spinkled throughout the rest of the eye)
  • PRODUCES COLOR VISION
  • recovery time
35
Q

Describe the types of cones

A

1) Red, Green, and Blue (60, 30, 10 percent of the eye respectively)
2) All colors are sensitive to lights that emit their respective color (i.e. red cone is sensitive to red light)
3) Cones absorbs red, green, and blue light
4) Cones are centered in the fovea

36
Q

What happens when light hits a rod?

A

1) When light hits the rod, it turns the rod off (typically on when light is not hitting rod)
2) Causes Bipolar cell to turn on
3) When bipolar cell turns on, this causes a retinal ganglion cell to turn on
4) retinal ganglion cell goes into the optic nerve and enters the brain

Summary:

1) Rod turns off
2) bipolar cell turns on (are usually off when rod is turned on)
3) retinal ganglion cell turns on
4) Retinal ganglion cell sends visual signals to the optic nerve (which are just the axons of the ganglion cells)
5) Visual signals (neural impulese) get sent to the brain

37
Q

What is the phototransduction cascade?

A

1) Series of steps, at the molecular level, that turns a rod off; which allows for conversion of light to neural impulses

Note: makes brain recognize there is light entering the eye

38
Q

Describe structure of a rod.

A

1) Multimeric protein with 7 discs stacked on top of one another
2) Discs are covered with proteins
3) Important Protein: Rhodopsin (photopsin in a cone) that has a molecule known as 11-cis retinal
4) Transducin Molecule is attached to rhodopsin (has alpha, beta, and gamma parts)
5) cyclic GMP Photodiesterase (PDE): second important protein

39
Q

What happens when light hits the tail of the 11-cis retinal molecule in a rod? (phototransduction cascade)

A

1) Changes the conformation of the molecule (tail of the molecule is initially bent, light causes the tail to become straight)
2) Molecule becomes 11-trans retinal
3) This also changes the shape of the rhodopsin molecule
4) Change in shape of rhodopsin causes transducin to break off
5) alpha subunit of transducin then attaches to PDE (this activates PDE)
6) Activated PDE takes cGMP and converts it to GMP (increasing concentration of GMP)
7) Sodium channels on the rod (normally opened when cGMP is attached), begin to close b/c of the decrease in cGMP concentration
8) Decrease in sodium entering the cells causes hyperpolarization of the rod, causing it to turn off
9) When the rod turns off, this turns on the bipolar cell
10) Retinal ganglion cell is activtaed.
11) Neural impulse is sent to the nerve and to the brain

NOTE: Same exact process happens in a cone

40
Q

What is the blindspot and where is it located?

A

1) Part of the retina directly in the front of where the optic nerve exits the back of the eye
2) There are no photo receptors present in the area

41
Q

Why is the fovea (dimple in the retina) able to allow an individual to have detailed vision?

A

1) there no axons in way of light so get higher resolution (allows light to hit cones directly)
2) At the periphery - light has to go through bundle of axons and some energy lost (less light gets to the rod, which doesn’t provide detailed vision)

42
Q

What does visual field processing allow?

A

allows our brain to make sense of what we’re looking at

43
Q

What is the nasal side of the eyes?

A

Part of the eye light hits that is closest to the nose (left side of the eye for the R eye; right side of the eye for the left eye)

44
Q

What is the temporal side of the eyes?

A

Part of the eye light hits that is closest to the temple (Left side of the left eye, right side of the right eye)

45
Q

Right visual field goes to the left side of the brain and left visual field go to the right side of the brain. How does this work?

A

1) Optic nerve connects brain to the eye
2) Optic Chiasm: where optic nerves converge
3) Optic nerves break off again into 2 separate nerves before entering the brain
4) Visual signals that hit the nasal sides of the eyes each travel along the inner part of the optic nerve and cross over to the opposite nerve at the optic chiasm
5) Visual signals that hit the temporal side of each eye travels along the outer part of the optic nerve and continues along the nerve into the brain without crossing over to the other nerve at the optic chiasm

46
Q

What is feature detection and what does it involves?

A

1) breaking down an object into smaller components in order to make sense of wha you are looking at
2) color, form, motion

47
Q

How does the brain recognize color?

A

1) Via cones (trichromatic theory)
2) when light hits a cone, that cone reflects its respective color
3) this fires an action potential to the brain (information regarding the color is sent to the brain)

48
Q

How does the brain recognize form?

A

1) Distinguish boundaries and shape of the object

2) Done via Parvocellular Pathway

49
Q

What is the parvocellular pathway responsible for?

A

1) good at spatial resolution
2) distinguishes boundaries, shape, and color of still objects
3) This pathway has poor temporal resolution (which involved motion) – makes it difficult to have detailed vision of a moving object
4) Cones are responsible for this

50
Q

What allows our brain to encode for motion?

A

Magnocellular pathway

51
Q

What does the Magnocellular pathway have that the parvocellular pathway does not, which helps to to pay attention to detail, even when an object is in motion?

A

1) temporal resolution (and has poor spatial resolution)
2) Rods responsible
3) Does not involve color, only encodes for motion

52
Q

What is parallel processing?

A

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

53
Q

Transmission

A

electrical activation of one neuron by another

54
Q

Perception

A

conscious sensory experience of neural processing

55
Q

Processing

A

neural transformation of neural signals into perception

56
Q

Transduction

A

energy transformed from one form to another (i.e. light energy to electrical energy by photopreceptors)

MCAT PSYCHOLOGY (7 decks)

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