Chapter Two

Question 1

• What is vision based on?

Answer 1

Vision - based on visible light (light energy or photons)

Question 2

Electromagnetic Spectrum

Answer 2

Electromagnetic Spectrum

• Electric energy sent on waves
• electrical energy spreading microscopic waves

Question 3

Wavelengths

Answer 3

Wavelengths - distance between the peaks of electromagnetic waves

• humans perceive 400 - 700 nanometers (nm) - our visible light
• Short wavelength = blue
• Middle wavelength = green
• Long wavelength = yellow, orange, red

Question 4

Visible light

Answer 4

Visible light - humans perceive 400 - 700 nanometers (nm)

• Short wavelength = blue
• Middle wavelength = green
• Long wavelength = yellow, orange, red

Question 5

• Know the structure of the eye: pupil, cornea, lens, ciliary muscles, retina, and optic nerve. (pp. 22-23)

Answer 5

Structure of the Eye:
Pupil- an opening for light to enter
Cornea - nonadjustable clear part covering the front; 80% of where images are focused
Lens - adjustable to deal with distance; 20% of where images are focused
Ciliary muscles- help shape the lens to focus on far and close objects
Retina - back of eye containing rods and cones
Optic Nerve - sends electrical signals to the brain

Question 6

Pupil

Answer 6

Pupil- an opening for light to enter

Question 7

Cornea

Answer 7

Cornea - nonadjustable clear part covering the front; 80% of where images are focused

Question 8

Lens

Answer 8

Lens - adjustable to deal with distance; 20% of where images are focused

Question 9

Ciliary muscles

Answer 9

Ciliary muscles- help shape the lens to focus on far and close objects

Question 10

Retina

Answer 10

Retina - back of eye containing rods and cones

Question 11

Optic Nerve

Answer 11

Optic Nerve - sends electrical signals to the brain

Question 12

• What are rods and cones?

Answer 12

Rods and cones contain light-sensitive chemicals called visual pigments
Rods - Large, cylinder shape, depth and shape
Cones - small, cone-like, color and detail

Question 13

Visual Pigments

Answer 13

Visual Pigments - react to light and create electrical signals to the optic nerve

Question 14

• Know the two transformations operated in the retina to see. (pp. 23)

Answer 14

2 Transformations:

1. Light from object turns into image
2. Image turns into electrical signal in the brain

Question 15

• What is accommodation? (pp. 24)

Answer 15

Accommodation
- unconscious adjustment of the len’s shape to focus image

• ciliary muscles tighten -thicker curvature of the lens
  +bends light rays in lens to reach the retina for sharper image
  +focus on near objects
• ciliary muscles relax - thinner curvature of lens
  +focus on far objects

Question 16

• What is the difference between near point (pp. 24) and far point (pp. 25)?

Answer 16

Accommodation has its limits - image becomes blurry when it is no longer close to your near or far points

Near Point - the point at which a close object can be seen clearly without being blurry

Far point - the point at which a far object can be seen clearly without being blurry

Question 17

Presbyopia

Answer 17

Presbyopia - “old eye”

• distance of near point increases with age
• lens harden and ciliary muscles weaken
• corrective lenses (glasses) are needed

Question 18

Myopia

Answer 18

Myopia (nearsightedness)

• close objects = clear
• far objects = blurry

Two possible problems for Myopia:
1. Refractive myopia = cornea and/or lens bend too much light
2. Axial myopia = eyeball is long
-Both problems do not reach retina properly
+farpoint reaches in front of the retina

Question 19

Hyperopia (pp. 24-26)

Answer 19

Hyperopia (farsightedness)

• close objects = blurry
• far objects = clear
• near point reaches behind the retina
  +eyeball is too short

Question 20

What is transduction?

Answer 20

Transduction - change from environmental energy to electrical energy in the brain

Question 21

What are the two parts of the visual pigment molecule? Where are they located? (pp. 26-27)

Answer 21

Visual Pigment Molecules - contains millions of light-sensitive chemicals to create electric energy
-absorbs light energy (photons) to see

LOCATED IN THE RETINA (RODS AND CONES

in the outer segment of the rods and cones of the retina

Molecules - a group of atoms stuck together; microscopic
Contains 2 parts:
-Opsin - long protein
-Retinal - light sensitive; smaller molecule attached to the opsin

Question 22

• What is isomerization? (pp. 27)

Answer 22

Isomerization - Change of molecule’s shape
-retinal bends straight on the opsin

This change triggers a chemical chain reaction

• activates a million other visual pigment molecules
• generates electrical energy in the rods & cones

Question 23

• Where are the rods and cones located? (pp. 28)

Answer 23

Distribution on the retina
Fovea - smaller area, containing only cones; 50,000 cones
Peripheral - outside of fovea, contains more rods than cones; 120 million rods/ 6 million cones

Question 24

macular degeneration (pp. 28),

Answer 24

common in older people, destroys the cone rich fovea and a small area that surrounds it. tis creates a blind region in central vision, so when a person looks directionally at something, he or she loses sight of it.

Question 25

retinitis pigmentosa (pp. 29)

Answer 25

Degeneration of the retina that is passed from one generation to the next. attacks peripheral visual field

Question 26

- What and where is the blind spot? (pp. 28-29)

Answer 26

Blindspot - absence of the retina (visual receptor) | Located near the optic nerve where electrical signals go to the brain

Question 27

Know the three adaptation curves. What are they? (pp. 29-31)

Answer 27

3 Adaptation Curves 1. Cones - 3-5 minutes to level off, reach maximum sensitivity 2. Rods - higher sensitivity to dark; 20 - 30 minutes to level off, reach maximum sensitivity 3. Rod- cone break - when cones cannot adapt any longer; the rods continue to adapt.

Question 28

What is visual pigment regeneration?

Answer 28

Visual Pigment Regeneration - Pigment regeneration responsible for sensitivity in the dar - Retinal need to reattach to opsin - Cone pigments - 6 minutes to regenerate - Rod pigments - more than 30 minutes

Question 29

What is visual pigment bleaching? (pp. 31-32)

Answer 29

Visual Pigment Bleaching - Molecule: retinal breaks apart from opsin - Bleaching: pigment (color) becomes lighter - Not useful for vision when bleached - you cannot see - i.e. walking from a dark room to the sun outside

Question 30

2 important relationships between perception and physiology (NOT ON STUDY GUIDE)

Answer 30

2 important relationships between perception and physiology 1. Sensitivity to light depends on visual pigments 2. Speed of sensitivity depends on chemical reaction (regeneration)

Question 31

- Understand the cone and rod spectral sensitivity curves. (pp. 32-34)

Answer 31

Spectral Sensitivity Curves -To sense color from wavelengths in rods and cones - Spectrometer - device to see monochromatic light - Rods - more sensitive to / in the dark - Cones - more sensitive to / in the light

Question 32

- Know the structure of a neuron: cell body, dendrites, and axon (also known as nerve fiber) (pp. 35)

Answer 32

See picture

Question 33

- Know the pathways of the visual system from the eye to the striate cortex (pp. 35)

Answer 33

Retina --> Optic Nerve --> Lateral Geniculate Nucleus (thalamus) --> Primary Visual Cortex

Question 34

- When do electrical signals of a neuron happen? Know the milliVolts (mV) of the resting potential and action potential. What are the basic properties of action potentials (i.e., propagated response, refractory period, and spontaneous activity)? (pp. 36-38)

Answer 34

Action potential jump to +40mv, resting -70mv Propagated response Refractory period Spontaneous activity

Question 35

- How do chemicals affect the electric signal of a neuron (i.e., an action potential, Na+ ions, K+ ions)? (pp. 38-40)

Answer 35

``` K+ = potassium Na+ = sodium - inside axon ``` DOUBLE CHECK WHAT DOES WHAT ``` Sending electrical signals chemical substance (neurotransmitters) - lets other neurons know whether to fire or not - relies on electrical signal to transmit ``` • Axons contain ions (electrically charged molecules) in & outside of membrane • Note: more concentration of negative charged ions inside axon during resting potential • During action potential: - Sodium ions (Na+) get inside axon - Potassium (K+) gets outside • Sodium (Na+) / Potassium (K+) pump: - Helps return axon to resting potential

Question 36

synapse

Answer 36

synapse - a tiny space between neurons where neurotransmitters send electrochemical info

Question 37

neurotransmitters

Answer 37

neurotransmitters - chemicals released in the synapse; determines electrical signal

Question 38

depolarization

Answer 38

depolarization - excitatory response, triggers action potentials, more positive ions inside axon

Question 39

hyperpolarization

Answer 39

hyperpolarization - inhibitory response, prevents action potentials, more negative ions inside axon

Question 40

- What are neural circuits? Where do the electrical signals sent from the visual receptors (rods and cones) go in the retina? (pp. 41)

Answer 40

Neural Circuits - a group of interconnected neurons Travel to the bipolar cells and then to the ganglion cells.

Question 41

- Know how neural convergence and non-convergence affect the sensitivity and acuity for rods and cones (pp. 40-44

Answer 41

Neural Convergence - where MULTIPLE neurons synapse onto a SINGLE neuron (quantity) Non-neural Convergence - where a SINGLE neuron synapse onto another SINGLE neuron (quality) visual receptors (rods) have more convergence

Question 42

sensitivity

Answer 42

sensitivity - ability to process light

Question 43

acuity

Answer 43

acuity - ability to process details

Question 44

Convergence in rods and cones

Answer 44

Rods- more convergence; high sensitivity; poor acuity Cones- lack of convergence; low sensitivity, greater acuity