L10 Retina and Visual Pathways Flashcards
_____________of photoreceptors contain light sensitive proteins called _______ (absorbs photon=> conformational change => membrane depolarization)
Outer Segments of photoreceptors contain light sensitive proteins called Opsins (absorbs photon=> conformational change => membrane depolarization)
Describe the sequence of events that occurs once a photon hits a Photoreceptor
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)
Photoreceptors in ____________ of light crank out neurotransmitters (_______)
Light ________ Activity of photoreceptor cells (_________POLARIZES)
Photoreceptors in ABSENCE of light crank out neurotransmitters (Glutamate)
Light REDUCES Activity of photoreceptor cells (HYPERPOLARIZES)
Rods vs. Cones
- Light Sensitivity
- Photopigments
- Amplification
- Temporal Resolution
- Acuity?
Photoreceptor (Graded Potentials): constantly release glutamate: stop when exposed to light
Various Types of Cells in the Retina? (Potential Type?)
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
Cell type responsible for LATERAL communication across retina (adjacent regions influence each other)
Horizontal Interneurons
Magnocellular vs. Parvoceullar?
Resolution of an image determined by _______ and ________ of receptive fields
_______ contribute to larger receptive field and are more numerous in periphery
Resolution of an image determined by DENSITY and SIZE of receptive fields
RODS contribute to larger receptive field and are more numerous in periphery
On vs. Off Center Cells? Effects on Glutamate release and Ganglion cell firing?
Affect on ON-Center Bipolar Cell of light shining on adjacent Surround Cone?
Temporal Hemiretinas:
- Visual Field _____________ to eye
- Fibers _____________
Nasal Hemiretinas:
- Visual Field __________ to eye
- Fibers _________________
Temporal Hemiretinas:
- Visual Field CONTRALTERAL to eye
- Fibers run IPSILATERALLY
Nasal Hemiretinas:
- Visual Field IPSILATERAL to eye
- Fibers DECCUSATE at optic chiasma
After Optic Chiasma, _________carries fibers conveying information about _________ Visual Field to the ________ and _________
After Optic Chiasma, Optic Tract carries fibers conveying information about CONTRALATERAL Visual Field to the Thalamus and Cortex
Where Does Output of the Retina Go?
- Majority (90%) of RG axons project to the _______________ => ______________________
- Some project to the _________ => ____________
- Some project to the ____________
- Axons to the Superficial Layer?
- Axons to the Deep Layer?
- Also plays a role in ____________
- Majority (90%) of RG axons project to the Lateral Geniculate Nucleus (Thalamus) => Optic Radiations (Geniculo-Calcarine Tract)
- Some project to the Pretectum => Edinger-Westphal Nucleus => Control the Pupil
- 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
Where does the correlation of information from left and right hemiretinas begin?
What is this information used to do?
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)
Course of the Superior and Inferior Optic Radiations (Geniculo-Calcarine Tract)?
Which visual field are each responsible for?
What is this Visual Field Defect called?
What lesion is it caused by?
Right Visual Field Blindness
Lesion to Optic nerve
What is this Visual Field Defect called?
What lesion is it caused by?
Bitemporal Hemianopia
Lesion at Optic Chiasm
What is this Visual Field Defect called?
What lesion is it caused by?
Homonymous Hemianopia
Lesion at Optic Tract
What is this Visual Field Defect called?
What lesion is it caused by?
Homonymous Quadrantopia
Lesion AFTER the Lateral Geniculate Body
