Lecture 8: Vision II Flashcards
What are the layers of the retina (in order)?
Photoreceptors, horizontal cells, bipolar cells, amacrine cells, ganglion cells
Photoreceptors
Rods, cones; transmit signals to outer plexiform layer, synapse with bipolar and horizontal cells
Horizontal cells
Transmit signals from rods/cones to bipolar cells; transmits signals to outer plexiform layer; output always inhibitory
Bipolar cells
Transmit signals from rods/cones/horizontal cells; transmit signals to inner plexiform layer; synapse with amacrine, ganglion cells
Amacrine cells
Interneurons that help analyze visual signals before the leave the retina
Ganglion cells
Transmit signals from retina to brain; axons make up optic nerves
What cells make up the optic nerves?
A. Horizontal cells
B. Ganglion cells
C. Bipolar cells
D. Amacrine cells
B. Ganglion cells
What is the neuronal pathway for cones?
3 neurons: Cones, Bipolar cells, Ganglion cells
What is the neuronal pathway for rods?
4 neurons: Rods, Bipolar cells, Amacrine cells, Ganglion cells
What neurotransmitter is involved with signaling between rods/cones and bipolar cells?
A. GABA
B. Glycine
C. Glutamate
D. Dopamine
C. Glutamate
What part of the eye does not contain any rods?
Central fovea
W ganglion cells
Increased sensitivity to dim light, most excitation from rods; 40% of all ganglion cells
X ganglion cells
Responsible for all color vision; 55% of all ganglion cells
Y ganglion cells
Respond to rapid changes in visual image, apprise CNS when new visual event occurs; 5% of all ganglion cells
What is the function of the lateral geniculate nucleus?
Receives input from the optic nerve and relays information from optic tract to visual cortex
How much decussation occurs in the optic chiasm?
A. 50%
B. 40%
C. 25%
D. 75%
A. 50%
Which layers of the LGN receive signals from the lateral half of ipsilateral retina?
II, III, V
Which layers of the LGN receive signals from the medial half of opposite retina?
I, IV, VI
Layers I and II of the LGN
Large neurons receive input from Y ganglion cells; rapidly conducting, only transmits black and white
Layers III through VI of the LGN
Small to medium size neurons receiving input almost entirely from large X type ganglion cells; moderate conducting pathway for color and point-point transmission
Transmission gating
Regulation of how much of the signal is allowed to pass to the visual cortex by LGN
What are the 2 sources of gating control?
Corticofugal fibers from the primary visual cortex and reticular areas of the mesencephalon
Layer IV of the primary visual cortex
Geniculocalcarine fibers terminate here; X signals terminate in IVcalpha, Y signals terminate in IVcbeta and IVa
Color blobs
Special column-like areas receiving lateral signals from adjacent visual columns; located in secondary visual areas
