Visual Pathway

Question 1

What is the first structure in the visual pathway?

Answer 1

Retina

The retina is where light is transduced into electrical impulses.

Question 2

What are the main components of the visual pathway?

Answer 2

Optic nerve, optic chiasm, optic tracts, lateral geniculate nucleus, optic radiations, primary visual cortex

These components work together to transmit visual information from the retina to the brain.

Question 3

What visual field defect results from lesions at the optic chiasm?

Answer 3

Bitemporal hemianopia

This condition is often caused by a pituitary adenoma.

Question 4

What type of visual field defect is caused by retrochiasmal lesions?

Answer 4

Contralateral homonymous field defect

This means that the defect occurs in the same visual field of both eyes.

Question 5

What does a lesion through the parietal optic radiation lead to?

Answer 5

Inferior quadrantanopia

This refers to a loss of vision in the lower quadrant of the visual field.

Question 6

What does a lesion through the temporal optic radiation lead to?

Answer 6

Superior quadrantanopia

This refers to a loss of vision in the upper quadrant of the visual field.

Question 7

What is the primary function of the magnocellular pathway?

Answer 7

Motion detection, depth perception, low acuity, high contrast sensitivity

The magnocellular pathway is vital for rapid visual processing.

Question 8

What is the primary function of the parvocellular pathway?

Answer 8

High acuity vision, color processing, low contrast sensitivity

This pathway is essential for detailed visual tasks.

Question 9

How many layers does the lateral geniculate nucleus (LGN) have?

Answer 9

6 layers

Each layer has different inputs from the eyes.

Question 10

Which layers of the LGN receive fibers from the ipsilateral eye?

Answer 10

Layers 2, 3, and 5

These layers process visual information coming from the same side of the body.

Question 11

Which layers of the LGN receive fibers from the contralateral eye?

Answer 11

Layers 1, 4, and 6

These layers process visual information coming from the opposite side of the body.

Question 12

What is retinotopic mapping?

Answer 12

The order of retinal neurons is maintained throughout the visual pathway

Neighboring regions of the image are represented by neighboring regions of the visual cortex.

Question 13

What does the optic nerve consist of?

Answer 13

Axons of retinal ganglion cells

The optic nerve contains around 1.2 million axons.

Question 14

List the four main portions of the optic nerve.

Answer 14

• Intraocular
• Intraorbital
• Intracanalicular
• Intracranial

Each portion has different anatomical characteristics.

Question 15

What is the function of the superior colliculus?

Answer 15

Rapid motor reflexes and visual association pathways

It plays a role in coordinating eye movements and reflexes.

Question 16

What type of retinal ganglion cells are involved in the magnocellular pathway?

Answer 16

Parasol retinal ganglion cells

These cells are large and have complex dendritic networks.

Question 17

What type of retinal ganglion cells are involved in the parvocellular pathway?

Answer 17

Midget retinal ganglion cells

These cells are small and have a simple dendritic network.

Question 18

True or False: The magnocellular and parvocellular pathways mix at any point in the visual pathway.

Answer 18

False

These pathways remain distinct from the retina to the visual cortex.

Question 19

What visual defect does a lesion at the level of the occipital lobe usually result in?

Answer 19

Homonymous hemianopia with macular sparing

This is thought to be due to the dual blood supply to the occipital lobe.