4. Vision - Retina Flashcards
cells in the eye which carry information about colour, shape, movement, etc
classic retinal ganglion cells (RGCs)
classical retinal ganglion cells project to the:
lateral geniculate nucleus (LGN), then the primary visual cortex
intrinsically photosensitive retinal ganglion cells (ipRGCs) project to the:
suprachiasmatic nucleus (SCN) and the paraventricular nucleus (PVN) to form the retinohypothalamic tract
OR
the intergeniculate leaflet (IGL) and olivary pretectal nucleus (OPN)
the suprachiasmatic nucleus (SCN) and paraventricular nucleus (PVN) are involved in:
circadian rhythms (stimulate melatonin release from the pineal gland)
the olivary pretectal nucleus projects through the _____ to activate motor neurons in the ____ that controls muscle of the ____
Edinger-Westphal nucleus (EW), ciliary ganglion, iris
a light-sensitive receptor protein involved in visual phototransduction
rhodopsin
what are the two major types of eyes
compound eyes and camera type eyes
rhodopsin is a photopigment composed of two parts:
retinal and opsin
a protein with seven transmembrane alpha-helices (GPCR) and is part of the rhodopsin photopigment
opsin
a chromophore which absorbs light, is derived from vitamin A, and is part of the rhodopsin photopigment
retinal
in vertebrates, _____ is attached to the seventh transmembrane domain of the opsin protein
11-cis retinal
11-cis retinal is converted, by light, to:
all-trans retinal
the conversion of 11-cis retinal to all-trans retinal causes a conformation change in the opsin to produce:
activated rhodopsin (results in a G protein cascade)
list the eight major parts of the vertebrate eye
- lens
- iris
- pupil
- cornea
- ciliary body
- retina
- fovea
- optic nerve
in the retina, light has to pass through the ganglion cells to activate:
the photoreceptors
list the five major cell types found in the retina
- photoreceptors (rods and cones)
- bipolar cells
- retinal ganglion cells (RGCs)
- horizontal cells
- amacrine cells
do photoreceptors produce action potentials?
no, the axons are too short (just not worth it)
which are larger and more abundant: rods or cones?
rods
in rods, the pigment rhodopsin is embedded in:
membranes arranged in the form of disks (not continuous with the outer membrane of the cell)
in cones, the pigment rhodopsin is embedded in:
infolded membranes that are continuous with the surface membrane
true or false: light depolarizes vertebrate photoreceptors
false, light hyperpolarizes photoreceptors
list the four steps involved in hyperpolarization of photoreceptors
1) light is absorbed and rhodopsin becomes activated
2) the G protein transducin is stimulated (GTP exchanged for GDP on the alpha subunit)
3) the alpha subunit separates and activates cGMP phosphodiesterase, which catalyzes the breakdown of cGMP to 5’-GMP
4) as concentration of cGMP decreases, cGMP detaches from cation channels, which causes them to close (less Na+ enters the cell and the cell hyperpolarizes)
each transducin can activate at least 12-14 molecules of:
cGMP phosphodiesterase
each cGMP phosphodiesterase hydrolizes 100 000s of:
cGMPs