Vestibular System & Visual System

Question 1

What are the functions of the vestibular system?

Answer 1

Balance, equilibrium posture, head, body, eye movement

Question 2

What is the signaling Mechanism of the Vestibular Sacs?

Answer 2

The calcium crystals (otoliths) move gelatinous cap upon head movement or linear head acceleration. The embedded stereocilia of the hair cells move and change the polarization and rate of action potentials

Question 3

What do the semicircular canals respond to? How do they do this?

Answer 3

Signal head’s rotational acceleration; The inertial resistance of the endolymph fluid induces bending of the Cupula and stereocilia

Question 4

What is the central vestibular pathway?

Answer 4

Hair cells –> Scarpas’a Ganglia –> Vestibularcochlear Nerve –> Vestibular Nuclei (brainstem) –> Thalamus (VP)–> Somatosensory cortex, Cranial Nerves, Cerebellum

Question 5

What is the Vestibulo-Ocular Reflex

Answer 5

Fixed line of sight (as your head moves left, your eyes move right to keep on point of focus)

Question 6

What are the 3 characteristics that determine perceived color?

Answer 6

Hue (wavelength/color), Brightness (Amplitude), Saturation(“purity” of wavelength)

Question 7

What is the cell in the retina that fires action potentials?

Answer 7

Ganglion Cells

Question 8

What is the direct pathway in the retina?

Answer 8

Photoreceptors –> Bipolar Cells –> Ganglion Cells

Question 9

What do horizontal cells do?

Answer 9

Receive input from photoreceptors and project to other photoreceptors and bipolar cells

Question 10

What do Amacrine cells do?

Answer 10

Receive input from bipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells

Question 11

What are the 2 main types of photorecptors?

Answer 11

Rods and Cones

Question 12

What are the characteristics of the peripheral retina?

Answer 12

High ratio of rods to cones, high ratio of photoreceptors to ganglion cells, more sensitive to light

Question 13

What is the fovea? What are the characteristics?

Answer 13

Pit in retina where outer layers are pushed aside; 1:1 ratio of photoreceptors to ganglion cells, all cones

Question 14

What is the dark current?

Answer 14

Rod outer segments are depolarized in the dark because of steady influx of Na+

Question 15

What happens to photoreceptors in response to light?

Answer 15

Hyperpolarize

Question 16

What is the main function of rods?

Answer 16

To detect overall level of light

Question 17

What is the main function of cones?

Answer 17

Color vision

Question 18

What is the receptive field?

Answer 18

Area of retina that, when stimulated with light, changes a cell’s membrane potential

Question 19

What kind of receptors do Off bipolar cells have? What happens in the dark?

Answer 19

Ionotrophic recepotrs; Depolarize in the dark

Question 20

What kind of receptors do on bipolar cells have? What do they do in response to light?

Answer 20

Metabotrophic receptors; Depolarize in light

Question 21

What happens in response to light on the center of an on-center bipolar cell?

Answer 21

Depolarization

Question 22

What happens in response to light on the surround of an on-center bipolar cell?

Answer 22

Hyper polarization

Question 23

What are the responses to light of an off-center bipolar cell?

Answer 23

Opposite of the on-center cells

Question 24

What are the types of ganglion cells? How do they differ?

Answer 24

M-type (large), P-type (small)

Question 25

How does the red-green color opponents work?

Answer 25

Red on center = lots of action potentials
Red on center & surround = some action potentials
Red on center & green on surround = few action potentials

Question 26

What is the optic pathway to the brain?

Answer 26

Retina –> optic nerve –> optic chaism –> Supra chiasmatic nucleus (brainstem) –> LGN (thalamus) –> optic radiations –> Occipital Lobe

Question 27

If you cut the left optic tract, what will happen?

Answer 27

Lose field of vision in left side of both eyes

Question 28

What does the superior colliculus do?

Answer 28

Orients the eyes in response to new stimuli

Question 29

What layer is the recipient of major LGN inputs?

Answer 29

Laver IV C

Question 30

What are the orientation selective cells?

Answer 30

outside layer IV C, simple cortical cells

Question 31

What are complex cells?

Answer 31

Direction specific, guide movements (dorsal stream)

Question 32

What is the dorsal stream of visual information?

Answer 32

Analysis of visual motion and the visual control of actions

Question 33

What is the ventral stream of visual information?

Answer 33

Perception of the visual world and the recognition of objects