Exam 2 Vision 3 Flashcards
What is the total amount of space that can be viewed by the retina when the eye is fixated straight ahead?
Visual Field
What is the ability of the eye to distinguish between two nearby points.
–depends mainly on the spacing of the photoreceptors in the retina.
•Visual Acuity
- The __________ is the projection of the visual world onto the retina.
- The image of the target is reversed on the retina by the lens system.
visual field
Why dont we notice our blind spot?
–During binocular viewing, the monocular visual fields overlap such that each field overlays the contralateral blind spot.
–During monocular viewing, the missing part of the visual field is neurally filled-in.
What are the projections from the retina?
Optic nerve
Optic Chiasm
Optic tract
What exits the left and right eyes at the optic disks and passes through holes in the floor of the skull?
Optic nerve
What is the joining of the optic nerves of each eye just above the pituitary gland?
- The axons originating in the nasal retinas cross from one side to the other (decussation).
- This crossing of fibers allows us to see in three dimensions.
Optic Chiasm
What are the axons projecting from the optic chiasm toward specific regions of the brain?
Optic Tracts
•Remember that light from the right binocular zone falls on the left ______ hemiretina and the right _____ hemiretina.
Left temporal
right nasal
•Information from the right visual hemifield is sent to the ______ side of the brain.
left
At the lateral geniculate nucleus (LGN), inputs from the two eyes are kept _______
separate
In the right LGN, the right eye (ipsilateral) axons synapse in LGN cells in layers ________
The left eye (contralateral) axons synapse on cells in layers ________
2, 3 and 5
1, 4 and 6
–The right LGN receives information about the _________ visual field.
left
What are the two ventral layers of LGN?
What retinal ganglion cells project here?
–The two ventral layers, 1 and 2, the magnocellular layers, contain large neurons.
•M-type retinal ganglion cells project here.
What are these features of?
- have relatively large receptive fields.
- respond to stimulation of their receptive field centers with a transient burst of action potentials.
- are insensitive to differences in wavelength.
- have features just like M ganglion cells.
- are activated by only one eye (monocular).
Features of magnocellular LGN neurons:
•Cells in the striate cortex that receive input from the ________________:
–have binocular receptive fields,
–sense brightness but not color,
–have direction selectivity which helps to analyze object motion
- move visual stimuli towards receptive field and then you see the response
- once they pass receptive field there is less stimulus
magnocellular pathway (M channel)
*nocturnal animals need to know which direction animal or prey is moving
•Cells in the striate cortex that receive input from the ____________:
–have binocular, rectangular receptive fields.
–are very sensitive to wavelength of light (red and green).
–are sensitive to stimulus orientation which helps to analyze object shape.
-as long as it is parallelly moved in receptor field you can see it
parvocellular pathway (P channel)
Name this retinal projection:
Internal biological clock
1) Synchronizes sleep/wake cycles among other biological rhythms.
2) These cycles are endogenous (internal).
3) External timing cues (zeitgebers) adapt the rhythm to the environment.
- sunlight, noise, social interactions, and alarm clocks
4) This clock can be reset.
- Jet lag, nocturnal employment.
•Regulates the timing of sleep but is not responsible for sleep itself.
Suprachiasmatic Nucleus
