Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Med Neuro Block 2 > Visual Systems 3: Central Pathways > Flashcards

Visual Systems 3: Central Pathways Flashcards

1
Q

The central visual system extends from the ________ to the ___________.

A
  • retina
  • striate cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Lateral Geniculate Nucleus:

A
  • Layers are segregated according to
    component cell characteristics and
    input:
    • Magnocellular (ventral 2) layers:
      contain large cells that receive input from parasol ganglion cells (red)
    • Parvocellular (dorsal 4) layers: contain small cells and receive input from midget ganglion cells (blue)
  • Functional divisions set up in the
    retina are retained
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do the fibers of the opitc nerve do at the optic chiasm?

A
  1. nasal fibers cross at the optic chiasm
  2. temporal fibers do not cross at the optic chiasm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Axons from the LGN innervate ____ in a ________ fashion

A
  • V1
  • retinotopic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Meyer’s loops contains fibers from which part of the visual field?

A
  • superior visual field
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What would happen if there was a lesion in Meyer’s loop?

A
  • Superior visual field defects (Contralateral Upper Quadratonopia)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q
  • Visual field map is _______ on the cortex.
  • Most V1 is buried in the __________.
A
  • inverted
  • calcarine sulcus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The retina of the right eye has a retinotopic map of ___________________.

A

both the left and right visual fields

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the visual fields and projections through the retina:

A

Consider the right retina:

  • Temporal division:
    • receives information about the left visual field (solid line)
  • Nasal division:
    • receives information about the right visual field (dotted line)
  • Retinal ganglion cell axons of the right eye exit the retina through the optic disk to form the optic nerve
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The right optic nerve will contain information from _________________.

A
  • one:
    • eye
  • both:
    • left and right visual fields
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the projections of the visual fields at the optic chiasm:

A
  • Nasal retina: decussate
  • Temporal retina: do not cross
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Fibers of the optic tract contain information of:

A
  • one:
    • visual field (contralateral visual field)
  • both:
    • left and the right eyes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The right optic tract would contain information of the ____________ from the nasal division of the _______ and the temporal division of the __________.

A
  • left visual field
  • left retina
  • right retina
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Damage to one of the optic nerves before it reaches the optic chiasm would result in:

A
  • loss of vision in that eye of origin
  • However, the patient would still be able to view the left and right visual fields using the undamaged eye
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Damage in the region of the optic chiasm would result in:

A
  • loss of vision from the nasal retina of both eyes
  • often patient complains of loss of peripheral vision (Bilateral hemianopia)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Damage in the region of the optic tract would result in:

A
  • loss of vision of the contralateral visual field represented in both eyes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does the light reflex do?

A

regulates pupillary size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Direct pupillary light reflex:

A

The response in the stimulated eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Consensual pupillary light reflex:

A

The response in the unstimulated eye

20
Q

The fibers that control the light reflex DO NOT synapse in the _____.

A

LGN

21
Q

Central Pathway (light relfex):

A
  • Afferent = CN II
  • **Efferent **= CN III
22
Q

Ganglion cells of the retina:

A

project bilaterally to pretectal nuclei

23
Q

Pretectal nucleus of midbrain:

A
  • projects crossed & uncrossed fibers ⇒ rostral Edinger‐ Westphal nucleus
    • in posterior commissure
24
Q

Edinger‐Westphal nucleus of midbrain:

A
  • gives rise to preganglionic parasympathetic fibers
  • which exit the midbrain with the oculomotor nerve
  • synapse with postganglionic neurons at the ciliary ganglion
25
Q

Ciliary ganglion of orbit:

A
  • gives rise to postganglionic parasympathetic fibers
  • which innervate the sphincter pupillae muscle of the iris
26
Q

What would happen if the Edinger-Westphal nucleus were unilaterally lesioned?

A
  • There would be a lack of pupillary response on the affected side
27
Q

Lesion of the pulvinar of the thalamus can cause _________.

A

hemineglect

28
Q

Superior Colliculus:

A
  • Mesencephalic laminated structure
  • Receives input primarily from the parasol cells
  • Produces output to:
    1. tectospinal tract: controlling head and trunk movements
    2. **brainstem nuclei: **controlling eye muscles
29
Q

What is the orienting reflex and where is it coordinated?

A

Superior Colliculus:

  • Input:
    • from fast moving stimuli in the periphery of your visual field
    • not high resolution area
  • To determine what it is: (e.g. threat level)
    1. Parasol retinal ganglion cells send a signal to the visual map in the superior colliculus
    2. Which then sends outputs to move the head and the eyes until the high resolution area of the retina is brought to bear on the stimulus
30
Q

Magnocellular cells (M cells):

A
  • Large cell bodies
  • Large receptive fields
  • Responses are fast and transient
  • High sensitivity to contrast
  • Cannot transmit information about color
  • Transmit information with high temporal resolution
31
Q

Parvocellular cells (P cells):

A
  • small cell bodies
  • small receptive fields
  • slower conduction velocity
  • lower sensitivity to changes
  • carry more information about details
  • can transmit information about color
  • provide information involving high spatial resolution
32
Q

What Brodmann’s area corresponds with the primary visual cortex (striate cortex)?

A

Area 17

33
Q

Extrastriate Cortex (Visual Association Cortex):

Charting

A
  • BA 18 & 19
  • V2, V3, V4 and V5
    • now V6, V8, VP, and numerous subdivisions of above
    • V5 is also referred to as area Middle Temporal (MT)
34
Q

Extrastriate Cortex (Visual Association Cortex):

Receptive Fields

A
  • V1: smallest
  • Generally get larger the
    farther from V1
  • In distal areas: can fill a whole
    quadrant of the visual field, or
    more
  • Large RFs in a small area of cortex
    means the precision of the map is
    poor    , andextrastriate cells are
    responsive over large areas
35
Q

Function of V4:

A

color discrimination

36
Q

Function of V5/MT:

A

Detection of motion:

  • speed & direction
37
Q

Cerebral Achromatopsia:

A
  • lack of color vision
  • Bilateral damage to the human homologue of V4:
    • produces sudden, global impairment in color perception
    • affecting the whole spectrum
  • Note:
    • different from color “blindness”
    • color “blindness” is caused by hereditary defects in photopigment genes
38
Q

Cerebral Akinetopsia:

A
  • lack of motion vision
  • Bilateral damage to the human homologue of MT:
    • produces sudden, global impairment in the ability to detect motion
    • Patients see changes in the position of items without seeing them move to get to the new position.
    • Motion is detected as “freeze frames” in a film
39
Q

V1 projects heavily to __.

A

V2

40
Q

What is the primary role of V2?

A
  • relay area
    • although there is some processing
41
Q

Streams of Processing:

Ventral Pathway

A

V1 ⇒V2 ⇒V4

  • “What is it?”
  • Temporal lobe
  • pathways for recognition of objects
    • e.g. shape, size, color, texture, etc.
  • Lesions here impair
    recognition
42
Q

Streams of Processing:

Dorsal Pathway

A

V1 ⇒V2 ⇒MT

  • “Where is it?”
  • Parietal lobe
  • Pathways for localization
  • Especially involved in directing visual attention to an object of interest
    • e.g. 3‐D position, trajectory, orientation, etc.
  • Lesions here impair the allocation of attention, a deficit termed “attentional neglect”
43
Q

Ventral Stream: Face Area in IT Cortex

A
  • Further downstream from V4
  • Receptive fields are huge
  • Cells have complex visual stimulus requirements for activation
    • sometimes including faces
  • Damage produces complex deficits
    • not simple visual discrimination problems
  • Damage to a part of the fusiform gyrus:
    • selective impairment in the recognition of faces
44
Q

Visuospatial Neglect:

A
  • Damage to parietal cortex, especially in the right hemisphere, causes “neglect” of the opposite half of visual space
  • However, visual thresholds are near normal when patient is forced to do tasks with only “neglected” hemifield
45
Q

Fate of Dorsal and Ventral Streams:

A
  • The ventral stream (which travels down the temporal lobe) and the dorsal stream (that heads to the parietal lobe) convey high level signals of objects and their location to high level brain structures:
  1. hippocampus (memory),
  2. prefrontal cortex (intention)
  3. limbic system (emotion)

Med Neuro Block 2 (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions