Class Lecture Notes: Vertebrate Eye Flashcards
Sclera
- outer part
- connective tissue
cornea
part of sclera
transparent, fixed lens
retina
inner
photoreceptors
ciliary body
produces aqueous humor, helps focus
vitreous humor
helps focus
lens
crystalline protein
makes fine adjustments in the focus of images
ciliary muscle
rounds up the lens, changing its light-bending properties to bring close images into focus
Photoreceptor cells
1) rods: see light/shades of gray
2) cones: see color
most dense at fovea (center of the visual field)
at least 3 types of cones: blue, green, and red
light travels through various layers before reaching the photosensors
Steps leading to the capture and transduction of the signal
5 Steps
- outer segments of rods with invaginations of plasma membrane containing rhodopsin, capture photons
- when exposed to photons a cascade of reactions is initiated by G protein, signal transduction closes sodium gated channels, membrane become hyper polarized
- photo-sensory cells release neurotransmitters, alters membrane potential of bipolar cells
- bipolar cells release neurotransmitter, ganglion cells generate AP
- two other layers, horizontal and amacrine, control lateral transmission of signals and adjust sensitivity to light level changes
horizontal cells
form synapses with neighboring photoreceptors and bipolar cells
amacrine cells
form local interconnections between bipolar cells and ganglion cells.
some highly sensitive to motion or to changing illumination
ganglion cells
closest to lens fire action potential
optic nerve
formed by the axons of the ganglion cells
photoreceptor pigments
vitamin a, retinal
retinal + opsin( protein)
rhodopsin
consists of opsin
present in rods
visual pigment
Photospin
in cones
respond to light by changing molecular shape 11-cis retinal to all-trans retinal
