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Neurology in Health & Disease > L10 Retina and Visual Pathways > Flashcards

L10 Retina and Visual Pathways Flashcards

1
Q

_____________of photoreceptors contain light sensitive proteins called _______ (absorbs photon=> conformational change => membrane depolarization)

A

Outer Segments of photoreceptors contain light sensitive proteins called Opsins (absorbs photon=> conformational change => membrane depolarization)

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2
Q

Describe the sequence of events that occurs once a photon hits a Photoreceptor

A

Outer Segments of photoreceptors contain light-sensitive proteins called Opsins

Opsins absorb photon=> induces a DECREASE in cGMP=> cGMP gated channels CLOSE=> HYPERPOLARIZATION => Decreased release of neurotransmitters (Glutamate)

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3
Q
A
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4
Q

Photoreceptors in ____________ of light crank out neurotransmitters (_______)

Light ________ Activity of photoreceptor cells (_________POLARIZES)

A

Photoreceptors in ABSENCE of light crank out neurotransmitters (Glutamate)

Light REDUCES Activity of photoreceptor cells (HYPERPOLARIZES)

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5
Q

Rods vs. Cones

  • Light Sensitivity
  • Photopigments
  • Amplification
  • Temporal Resolution
  • Acuity?
A

Photoreceptor (Graded Potentials): constantly release glutamate: stop when exposed to light

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6
Q

Various Types of Cells in the Retina? (Potential Type?)

A

Photoreceptors (Graded Potentials): constantly release glutamate: stop when exposed to light

  • Rods
  • Cones

Interneurons (Graded Potentials): relay information from multiple photoreceptors to provide the ganglion cells with their receptive field

  • Bipolar
  • Horizontal
  • Amacrine

Ganglion Cells (Action Potentials)

  • Magnocellular
  • Parvocellualar
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7
Q

Cell type responsible for LATERAL communication across retina (adjacent regions influence each other)

A

Horizontal Interneurons

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8
Q

Magnocellular vs. Parvoceullar?

A
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9
Q

Resolution of an image determined by _______ and ________ of receptive fields

_______ contribute to larger receptive field and are more numerous in periphery

A

Resolution of an image determined by DENSITY and SIZE of receptive fields

RODS contribute to larger receptive field and are more numerous in periphery

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10
Q

On vs. Off Center Cells? Effects on Glutamate release and Ganglion cell firing?

A
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11
Q

Affect on ON-Center Bipolar Cell of light shining on adjacent Surround Cone?

A
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12
Q

Temporal Hemiretinas:

  • Visual Field _____________ to eye
  • Fibers _____________

Nasal Hemiretinas:

  • Visual Field __________ to eye
  • Fibers _________________
A

Temporal Hemiretinas:

  • Visual Field CONTRALTERAL to eye
  • Fibers run IPSILATERALLY

Nasal Hemiretinas:

  • Visual Field IPSILATERAL to eye
  • Fibers DECCUSATE at optic chiasma
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13
Q

After Optic Chiasma, _________carries fibers conveying information about _________ Visual Field to the ________ and _________

A

After Optic Chiasma, Optic Tract carries fibers conveying information about CONTRALATERAL Visual Field to the Thalamus and Cortex

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14
Q

Where Does Output of the Retina Go?

  1. Majority (90%) of RG axons project to the _______________ => ______________________
  2. Some project to the _________ => ____________
  3. Some project to the ____________
  • Axons to the Superficial Layer?
  • Axons to the Deep Layer?
  • Also plays a role in ____________
A
  1. Majority (90%) of RG axons project to the Lateral Geniculate Nucleus (Thalamus) => Optic Radiations (Geniculo-Calcarine Tract)
  2. Some project to the Pretectum => Edinger-Westphal Nucleus => Control the Pupil
  3. Some project to the Superior Colliculus
  • Superficial Layer: projects to cerebral cortex via the Pulvinar Nucleus of Thalamus
  • Deep Layer: ALSO receives input from auditory and somatosensory stimuli, integrating them
  • Superior Colliculus also plays a role in Saccadic Eye Movements
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15
Q

Where does the correlation of information from left and right hemiretinas begin?

What is this information used to do?

A

Begins in the Lateral Geniculate Nucleus (LGN). LGN contains a retinotopic map with locations from each hemiretina next to each other. LGN performs anatomical calculations of retinal information BEFORE relaying this to Cortical Area 17 (aka. Striate cortex, V1 or Primary Visual Cortex) via the Optic Radiations (Baum’s/Meyer’s Loops)

This information is used to:

  • Control Vergence
  • Control Focus of the eyes
  • Control Eye Movements (Calculation of Velocity)
  • Integrates NON-VISUAL information (ie. Eye movements towards source of sound)
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16
Q

What are the Optic Radiations from the Lateral Geniculate Nucleus also known as?

A

Geniculo-Calcarine Tract

17
Q

Course of the Superior and Inferior Optic Radiations (Geniculo-Calcarine Tract)?

Which visual field are each responsible for?

18
Q

What is this Visual Field Defect called?

What lesion is it caused by?

A

Right Visual Field Blindness

Lesion to Optic nerve

19
Q

What is this Visual Field Defect called?

What lesion is it caused by?

A

Bitemporal Hemianopia

Lesion at Optic Chiasm

20
Q

What is this Visual Field Defect called?

What lesion is it caused by?

A

Homonymous Hemianopia

Lesion at Optic Tract

21
Q

What is this Visual Field Defect called?

What lesion is it caused by?

A

Homonymous Quadrantopia

Lesion AFTER the Lateral Geniculate Body

22
Q

INFERIOR Division of Optic Radiation (_________ Loop)

  • Courses through ____________ LOBE to __________ VISUAL CORTEX
  • Originates from ______ RETINA carries _________ VISUAL FIELD
A

INFERIOR Division of Optic Radiation (Meyer’s Loop)

  • Courses through TEMPORAL LOBE to INFERIOR VISUAL CORTEX
  • Originates from INFERIOR RETINA carries SUPERIOR VISUAL FIELD
23
Q

SUPERIOR Division of Optic Radiation (__________ Loop)

  • Courses through ________ LOBE to ___________ VISUAL CORTEX
  • Originates in __________ RETINA carries ____________ VISUAL FIELD
A

SUPERIOR Division of Optic Radiation (Baum’s Loop)

  • Courses through PARIETAL LOBE to SUPERIOR VISUAL CORTEX
  • Originates in SUPERIOR RETINA carries INFERIOR VISUAL FIELD
24
Q

Distinct information about the visual image is passed from the visual cortex to both the _________________ and ___________________

A

Distinct information about the visual image is passed from the visual cortex to both the Inferior Temporal Cortex and Parietal Cortex

25
Q

What lesion can result in Akinetopsia?

A

Lesions beyond the Visual Cortex can have complex effects on Visual Perception. V5 (Middle Temporal) Neurons are motion selective. Lesions here lead to Akinetopsia (impaired ability to perceive motion)

26
Q

What is the phenomena associated with seeing faces in inanimate objects? What cortex is associated with this?

A

Neurons in the Inferior Temporal Cortex can display responses to complex stimuli as they respond to form and color => Pareidolia

Neurology in Health & Disease (18 decks)

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