Visual System

Question 1

Structure: Focuses light on the fovea within the macula

Answer 1

Lens

Question 2

Structure: Changes the shape of the lens

Answer 2

Ciliary muscle

Question 3

Structure: Dilates/constricts pupil

Answer 3

Iris

Question 4

Structure: Location where the arteries and veins enter/exit the eye

Answer 4

Optic disc

Question 5

Structure: Important for peripheral, low light vision, provides gray scale

Answer 5

Rods

Question 6

Structure: Located in the peripheral retina

Answer 6

Rods

Question 7

Structure: Important for central vision and visual acuity, bright ligh vision, provides color

Answer 7

Cones

Question 8

Structure: Most located in the fovea

Answer 8

Cones

Question 9

Describe the how rods and cones effect your functionality

Answer 9

Cones: in daylight provide much greater spatial sensitivity in the central retina, however can’t perceive color in our periphery/in low light due to low cone density in the peripheral retina

Rods: In low light we are much more sensitive in our peripheral vision, however in daylight we have poor visual acuity in our periphery

Question 10

Describe phototransduction

Answer 10

Photopigments in photoreceptors absrob light resulting in change in photoreceptors membrane potential. Information is transmitted to ganglion cells which transmit AP through the optic n. to the brain

Light energy is transformed into neural energy before reaching the ganglion cells

Question 11

Visual area: Nasal receptors in the eye receive information from

Answer 11

Peripheral visual fields

Question 12

Visual area: Temporal receptors in the eye receive information from

Answer 12

Central visual fields

Question 13

Structure: Receptors that cross in the optic chiasm

Answer 13

Nasal receptors in the eye

Question 14

Structure: Receptors that remain on the same side

Answer 14

Temporal receptors in the eye

Question 15

Describe where the left hemifield information ends up

Answer 15

In the right cortex

Question 16

Structure: Connections from CN nuclei to the primary visual cortex

Answer 16

Optic radiations

Question 17

Describe where information from the superior and inferior optic radiation are coming from

Answer 17

Superior optic radiations carry information from the inferior visual field

Inferior optic radiations carry infromation from the superior visual field

Question 18

Describe the difference between the pupillary and consensual reflex

Answer 18

They are both elicited by the same stimulus: light in one eye

Pupillary reflex constricts the pupil in the eye that is directly stimulated

Consensual reflex constricts the pupil in the opposite eye

Question 19

Pathway: Afferent limb of the pupillary/consensual reflex

Answer 19

Retinogeniculocalcarine pathway

Question 20

Describe what can be differentiated between the pupillary reflex and accomodation reflex

Answer 20

Pupillary occurs in the brainstem and is unconscious

Accomodation occurs in the cortex and is conscious

Allows you to differentiate between the location of the problem

Question 21

Cortical area: Controls voluntary eye movement and requires planning

Answer 21

Frontal eye fields

Question 22

Cortical area: Provides information about the movement of visual objects

Answer 22

Occipital and temporal eye fields

Question 23

Cortical area: Provides spatial information for eye movements

Answer 23

Posterior parietal cortex

Question 24

2 Objectives of the Visual System

Answer 24

1. Keeping the position of hte eyes stable during head movements so that the environment does not appear to bounce (maintain stable gaze)
2. Directing gaze at visual targets

Question 25

Describe how maintaining a stable gaze is achieved

Answer 25

By the VOR: using information from head motion to keep eyes still

By the optokinetic reflex: using visual information to keep eyes still

Question 26

Describe how directing your gaze at visual targets is achieved

Answer 26

1. Saccades (fast movements to switch gaze)
2. Smooth pursuit (slow movements following a moving object)
3. Di/Convergence (movement toward/away from midline)

Question 27

Describe the function of the MLF

Answer 27

The medial longitudinal fasciculus connects several nuclei/axons (oculomotor, trochlear, abducens, vestibular, accessory) in order to coordinate head and eye movement