Visual System Flashcards
what are the main challenges of the visual system?
- detecting and coding the light signals (brightness, frequency)
- use the light information for visual and non-visual behaviours
- dynamically modulating this process in a context-specific manner
light is detected by ____ in a thin layer of the eye called the _____
photoreceptors, retina
photoreceptors project to _____, which project to the ______
bipolar cells, retinal ganglion cells (RGC)
what make up the optic nerve?
retinal ganglion cells
information dealing with the _________, crosses over at the ______ before terminating in the _______ of the ________.
contralateral visual field, optic chiasm, lateral geniculate nucleus, thalamus
where is the light initially detected in the visual system?
photoreceptors in the retina
at what point do RGC axons cross over in the visual pathway?
at the optic chiasm
where do RGCs project after leaving the optic nerve?
to the lateral geniculate nucleus and other non-visual areas
where does the info from the LGN ultimately project to?
the primary visual cortex in the occipital lobe
Label this diagram:
A: optic nerve
B: optic chiasm
C: LGN
D: optic radiation
E: striate cortex
F: optic tract
G: hypothalamus
H: pretectum
I: superior colliculus
circadian timekeeping: what is the typical activity pattern of nocturnal mice?
they are more active at night
circadian timekeeping: how do mice respond to changes in the light/dark cycle?
they are sharply entrained to dark and light cycles; if you change the phase of the light/dark cycle, they can phase shift to be concurrent.
what is the significance of IPRGCs in circadian timekeeping?
detecting light even without rods or cones
if mice are kept in complete darkness, they still keep a ______ but their cycle shifts a bit every day.
12 hour endogenous rhythm
what is lost if lesion in the retina?
endogenous rhythm
_____ are maintained in the absence of _____
circadian cycles, rod and cone photoreceptors
what are IPRGCs?
intrinsically photosensitive retinal ganglion cells
what does maintained circadian cycle in the absence of rod and cone photoreceptors indicate?
that there must be some way of detecting light without rods or cones, and that there must be some other photopigment elsewhere in the retina.
what did the study involving fluorescent dye injection into the hypothalamic suprachiasmatic nucleus aim to invesitgate?
examine the response of ganglion cells projecting to the SCN to light stimulation
fluorescent dye injection into the hypothalamic suprachiasmatic nucleus: where did the dye travel to?
through the optic nerves back into the retina to label ganglion cells that project to the SCN
fluorescent dye injection into the hypothalamic suprachiasmatic nucleus: what was the observed response in ganglion cells to light?
depolarization
fluorescent dye injection into the hypothalamic suprachiasmatic nucleus: what happened to the ganglion cell response when cobalt (Cav) channel blocker) was applied?
depolarlization persisted even w the application, indicating an independent light response
fluorescent dye injection into the hypothalamic suprachiasmatic nucleus: how did it provide evidence for the cells generating their own light response?
isolating retinal GCs from the retina and finding persistent responses confirmed the generation of an independent light response
what was observed when measuring the response of ganglion cells to light?
depolarization in response to light, indicating light sensitivity
