neurobio 915 ch 9 of Bear's book: the eye part 1 (cornea sclera retina fovea lens bipolar cell
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what is the sclera?
the white of the eye
what is the optic disk?
the region of the eye where the optic nerve fibers exit the retina
what is the fluid located between the cornea and the lens called?
what is the fluid located behind the lens called?
the lens is suspended by ligaments attached to the ____ _____
what is the site of the most refractive power in the eye?
what is the focal distance?
the distance from the refractive surface to the point where parallel light rays converge
what is a diopter?
the recpirocal of the focal distance in meters is a unit of measurement called the diopter
what is accomodation
changing the shape of the lens
what does visual acuity depend on?
it depends especially on the spacing of photoreceptors in the retina and the precision of the eye's refraction
true or false, the bipolar cel is the only source of output from the retina
false, the ganglion cell is the only source of output from the retina
the retina exhibits what kind of organization?
laminar organization, ie, the cells are organized in layers (inside-out layers)
diff. between rods and cones
rods detect black and white; they are more sensitive than cones in nightime lighting. cones detect color; they are more sensitive than rods in daytime lighting.
rods only ontain one type of pigment, but there are three types of cone, each containing a different pigment.
what is characteristic of the retinal periphery?
it contains a higher ratio of rods to cones. it also has a higher atio of photoreceptors to ganglion cells. Ther result of this is that the peripheral retina is more sensitive to light
what is the region of the retina that is most highly specialized for high0resolution vision?
in the dark, are the sodium channels opened or closed in rods? What is the molecular basis behind this? What is this movement of positive charge across the membrane called?
they are opened. sodium channels are stimulated to open (they are gated) by an intracellular second messenger called cGMP. Evidently, cGMP is continually produced in the photoreceptor by the enzyme guanylyl cyclase, keeping the Na channels open. The movement of positive charge across the membrane is called the dark current, since it occurs when the eye isn't exposed to light.
What occurs in regard to cGMP in rods when the rod is exposed to light.
Light reduces cGMP, causing the Na channels to lose, and the membrane potential becomes more negative.
photoreceptors __________ in response to light
what is the light-absorbing pigment in rods called?
what is the receptor protein of the rhodopsin molecule called?
rhodopsin can be thought of as a combination of two things. What are these two things?
it can be thought of as a receptor protein with a pre-bound chemical agonist
what is the prebound agonist of the rhodopsin molecule called?