Final: Sensory Systems: Eyes Slides

Question 1

What is the stimulus for eyes?

Answer 1

Light (have light-sensitive photoreceptors, that have pigment that senses light)

Question 2

What are the layers of the eye (outer to inner)?

Answer 2

Fibrous, vascular, neural

Question 3

What does each layer of the eye do (general)?

Answer 3

Fibrous: outer layer that provides protection with its fibers
Vascular: middle layer; where blood vessels are (provide nourishment)
Neural: inner layer; convert light info to electrical activity

Question 4

Parts of fibrous layer

Answer 4

Cornea and sclera

Question 5

Sclera function

Answer 5

Muscle attachment; allows precise movement of eyeballs without needing to move whole head

Question 6

Sclera structure and location

Answer 6

Majority of outer layer; white part of eye

Question 7

Cornea structure and location

Answer 7

On top of colored part of eye; thick, transparent membrane; convex

Question 8

Cornea functions

Answer 8

Protection but more importantly, corrects vision: convex shape corrects for distortion caused by movement of light through different medias (air then liquid)

Question 9

Parts of vascular layer (6)

Answer 9

Ciliary muscles (smooth), iris, pupil, zonular fibers, lens, choroid

Question 10

Choroid structure and function

Answer 10

Dark, pigmented layer to concentrate light (contains blood vessels)

Question 11

Zonular fiber function

Answer 11

Hold lens in place

Question 12

Ciliary muscle function

Answer 12

Accommodation: allows objects to be focused on retina no matter how near or distant they are (perfect camera that immediately adjusts) - changes shape of lens

Question 13

Pupil function

Answer 13

Opening for light to enter (covered by cornea)

Question 14

What type of muscles are ciliary muscles?

Answer 14

Involuntary smooth muscle

Question 15

When is the lens in each shape?

Answer 15

Flattened (ciliary muscles relax, zonular fibers tight): object is far
Rounded (ciliary muscles contract, zonular fibers loose): object is near

Question 16

What is the iris?

Answer 16

Colored part of the eye, with pupil at center

Question 17

How/when does pupil size change?

Answer 17

Dim light: radial smooth muscles contract, pupil dilates

Bright light: circular smooth muscles contract, pupil constricts (smaller)

Question 18

What happens in the neural layer?

Answer 18

Transduction: light converted to electrical activity, which is sent to the brain (neurons are here)

Question 19

Retina function

Answer 19

Contains photoreceptors to receive light and send it to brain through optic nerve

Question 20

Where is the highest density of photoreceptors?

Answer 20

Fovea centralis (high visual acuity)

Question 21

Types of cells in retina (5)

Answer 21

Ganglion cells, amacrine, bipolar, horizontal, photoreceptors (rods and cones)

Question 22

Ganglion cell function

Answer 22

Send signal to brain to be interpreted

Question 23

Amacrine cell function

Answer 23

Support synapses between bipolar and ganglion cells

Question 24

Horizontal cell function

Answer 24

Support/strengthen synapses between photoreceptors and bipolar cells

Question 25

What's the formula for sensation?

Answer 25

Need a receptor cell to synapse with neuron

Question 26

Pathway after light hits photoreceptors (rods/cones)

Answer 26

Rods and cones form connections with bipolar cells/neurons - bipolar cells form connections with ganglion cells - ganglion cells send signal to brain

Question 27

Difference between rods and cones

Answer 27

Rods: see B&W, more sensitive (extremely sensitive) to light, respond to low illumination Cones: see more details (color), less sensitive to light (need a lot of light for stimulation), respond to high illumination

Question 28

What do photoreceptors need to absorb light?

Answer 28

Pigment

Question 29

Pigment-containing protein in rods

Answer 29

Rhodopsin (starts process of electrical activity)

Question 30

Pigment-containing protein in cones

Answer 30

Photopsin

Question 31

Which pigment do the proteins in rods and cones contain?

Answer 31

Retinal

Question 32

Types of pigments in cones

Answer 32

Small (blue), medium (green), large (red) - size refers to wavelength

Question 33

When are cones and rods depolarized?

Answer 33

When we CAN'T see (counter-intuitive)

Question 34

When are cones and rods hyperpolarized?

Answer 34

When we CAN see

Question 35

Cones/rods in the dark

Answer 35

high cGMP levels - Na+ channels open - Na+ influx causes depolarization - Ca2+ channels open - Ca2+ influx - NT (glutamate) release - graded potential in bipolar cells

Question 36

What do Na+ channels in photoreceptors respond to?

Answer 36

Chemically gated; respond to cGMP (open with cGMP is high, closed when it's low)

Question 37

How does light induce chemical change in rods (start signal pathway)?

Answer 37

Retinal (pigment) changes chemical conformation - rhodopsin changes shape - activates transducin - alpha subunit translocates and activates phosphodiesterase - breaks down cGMP - Na+ channels close - hyperpolarization - no receptor potential, no NT release, no bipolar cell activity - brain IS getting signal

Question 38

What is transducin?

Answer 38

Very similar to G protein - has three subunits; alpha subunit translocates and activates phosphodiesterase in photoreceptors

Question 39

Rods/cones when exposed to light

Answer 39

low cGMP levels - Na+ channels closed - hyperpolarization - no NT release - no graded potential - nothing happens in bipolar cells - brain receives signal

Question 40

Visual field

Answer 40

When you fixate on one point, what you can see without moving your head

Question 41

Central vision

Answer 41

What you can see clearly in the visual field (in front of you)

Question 42

Peripheral vision

Answer 42

Outer edges of vision; things still visible but no longer clear

Question 43

Why is central vision clear?

Answer 43

Binocular vision: seeing things with both eyes visual fields overlap

Question 44

Where in the thalamus do visual signals go?

Answer 44

Lateral geniculate nucleus

Question 45

General neural pathway of vision

Answer 45

Nasal/temporal retina - optic nerve - optic chiasm - optic tract - lateral geniculate nucleus - visual cortex

Question 46

Which side of brain do nasal retina signals (from both R and L) go to?

Answer 46

Left side

Question 47

Which side of brain do temporal retina signals (from both R and L) go to?

Answer 47

Right side

Question 48

Macular degeneration

Answer 48

Lose central vision, but not peripheral vision

Question 49

Two optic nerves meet to form ____ _____

Answer 49

Optic chiasm

Question 50

What forms optic tracts?

Answer 50

Some axons cross to opposite side of brain