Visual System

Question 1

Retina

Answer 1

rods - peripheral
cones - central
fovea - point of fixation, highest visual acuity

Question 2

Visual Fields

Answer 2

normal vision - 60% overlap
light from temporal visual on nasal retina (VICE VERSA)
CN 2 fibers from nasal retina cross optic chiasm (carry info about contra side)

Question 3

Lateral Geniculate Nucleus

Answer 3

relay nucleus of thalamus

Question 4

Optic Radiations (geniculocalcarine tract)

Answer 4

fibers arise from LGN through retro and sublenticular portion of internal capsule
Meyer's Loop
retinotopically organized (superior fibers represent inferior visual field)

Question 5

Meyer’s Loop

Answer 5

passes through temp lobe

represent superior visual field

Question 6

Visual Cortex

Answer 6

terminate in cortex adjacent to calcarine fissue (superior field below fissure - VICE VERSA)
contra visual field represented
B occipital damage can lead to cortical blindness

Question 7

Visual Cortex Areas

Answer 7

17 - primary visual cortex

18, 19 - visual association cortex

Question 8

Hemianopia

Answer 8

loss of half of visual field

Question 9

Quadranopia

Answer 9

loss of one quadrant of visual field

Question 10

Homonymous

Answer 10

overlapping visual fields (i.e. R visual field of both eyes)

Question 11

Heteronymous

Answer 11

nonoverlapping field from each eye

Question 12

Superior Colliculus Pathway

Answer 12

receives direct retinal input from visual, SS, and auditory inpts
projects to reticular formation (generate saccades) and C-spine (orients head via TS tract, decussates in MB)
functions to orient head and eyes to visual (mostly), SS, and auditory stimuli
lesion = inability to orient to contra visual stimuli

Question 13

Retinohypothalamic Fibers Pathway

Answer 13

directly from retina

influence circadian rhythms

Question 14

Pupillary Light Reflex Pathway

Answer 14

tests integrity of connection between di and MB
circuit for direct response – retina (sensory) –> optic nerve –> optic tract –> pretectum –> CN III (motor)
for consensual response, fibers cross in pretectum to opposite side CN III

Question 15

Dorsal Stream

Answer 15

motor control, to post parietal cortex (ambient vision)
action vision, “where” pathway
info from fovea and retinal periphery = guide actions, about object characteristics
can operate in dim light
motor planning

Question 16

Ventral Stream

Answer 16

more conscious awareness of visual experience; to inferotemporal cortex (focal vision)
perception vision, “what” pathway
info from fovea
needs good lighting
conscious perceptual experience of vision, recognition of objects

Question 17

Lesion

Answer 17

Ventral - visual agnosia
Dorsal - optical ataxia
- can’t reach for object or adjust grasp to shape of object
- can pick object up but unaware of object’s dimensions or orientation

Question 18

Visual Proprioception

Answer 18

where we are relative to environment
post parietal lobe
optical flow provides info about environment

Question 19

Hypothalamus

Answer 19

influences behavior and autonomic, visceral, and pituitary function

Question 20

Thalamus: general

Answer 20

almost all sensory pathways relay in thalamus, then relays to cortex
motor from Cb and BG, inputs from limbic area
receive feedback information from areas to cortex to which they project

Question 21

Thalamus: topographical subdivisions

Answer 21

internal medullary lamina - divides into med/lat, splints ant
intralaminar nuclei - within IML, related to consciousness and pain transmission
lateral group - dorsal tier, ventral tier (VA, VL, VPL, VPM)
LGN and MGN - post extension of ventral tier, lateral (visual) medial (auditory)

Question 22

Post Thalamic Lesions

Answer 22

thalamic pain - similar to trigeminal neuralgia (i.e. intense pain triggered by SS stimuli
affects 1/2 body, resistant to analgesics
total or nearly total loss of sensation of contra heady and body (hemi-sensory analgesia)
DCML most severely affected; some recovery
produces sensory ataxia

Question 23

Thalamic Syndrome

Answer 23

contra thal pain, hemianesthesia, sensory ataxia

Question 24

Internal Capsule

Answer 24

between thal, caudate (medial), and lentiform nucleus (lateral)
ant limb - between lenticular nucleus and head of caudate
post - between lenticular nucleus and thal
genu - between ant and post limbs

blood supply by penetrating brances of mostly MCA - lenticulostriate arteries (some post cerebral)

Question 25

Internal Capsule: fibers

Answer 25

ant limb - carries to frontal cortex and from limbic portions of thal
post - ascending motor and sensory fibers (ventral tier, VPL - BG and Cb), descending CB and CS fibers

Question 26

Internal Capsule Stroke

Answer 26

post limb effected
hemiparesis and hemianesthesia can result - pure because no accompanying cognitive deficit

contra pure motor hemiplegia, hemisensory syndrome
contra homonymous hemianopia
with small areas involved - dysarthria and clumsy hand

Question 27

VA/VL - afferent, efferent

Answer 27

A - BG, Cb

E - supplemental and premotor motor areas

Question 28

VPL - afferent, efferent

Answer 28

A - DCML, ST tracts

E - area 3,1,2

Question 29

VPM - afferent, efferent

Answer 29

A - trigeminal system

E - area 3,1,2

Question 30

Lat Gen - afferent, efferent

Answer 30

A - optic tract

E - area 17

Question 31

Med Gen - afferent, efferent

Answer 31

A - BS auditory tracts

E - area 41

Question 32

ILN - afferent, efferent

Answer 32

A - ST/RF/ARAS

E - all areas of cortex, striatum