Lecture 22: Physiology of the Visual System Flashcards
What is rod-mediated vision called?
What is it called when rod-vision is lost?
Scotopic vision
Night Blindness
What is cone-mediated vision called?
Photopic Vision
What is mesopic vision called?
Rods and cones are both activated
Which retinal cells are horizontally oriented?
Horizontal cells
Amacrine cells
Which retinal cells are vertically oriented?
Receptor cells (Rods and cones)
Bipolar cells
Ganglion cells
What do rods and cones converge to?
Rods/Cones –> Bipolar Cells –> Amacrine Cells
Multiple rods converge to one bipolar cell but only one cone contacts one bipolar cells
In the retina, where are rods most abundant?
Where are cones most abundant?
Rods - Just off center
Cones - Directly center (fovea)
What NT is released by rods/cones?
Glutamate
Glutamate is constantly released despite dark/light
What visual conditions cause higher glutamate release?
Dark Current
Darkness: cells are constantly depolarized, releasing GLU
What visual conditions cause lower glutamate release?
Bright light
Light causes hyperpolarization –> less release of GLU
What is the specialized glutamate receptor found on on-center bipolar cells?
When are they activated?
mGluR6: Gi GPCR
- Activated with low concentrations of GLU (light)
- High concentrations of GLU will inactivate (dark)
What is the specialized glutamate receptor found on off-center bipolar cells?
When are they activated?
AMPA (non-NMDA)
- Activated with high concentrations of GLU (dark)
- Low concentrations of GLU will inactivate (light)
What NT causes depolarization of a ganglion cell?
Glutamate
Where are ganglion cells found?
What do ganglion cell axons form?
Inner Plexiform Layer
Fibers of Optic Nerve
In activation of a rod photoreceptor, what cell acts as an interneuron between bipolar cells?
What NT is released?
Amacrine cell
GABA or glycine (inhibitory)