Biomedical Engineering Reference
In-Depth Information
FIGURE 7-3
Schematic diagram
of the organization
of the retina
[Adapted from (Kolb,
Fernandez et al.,
2009) with
permission]
FIGURE 7-4
Sensitivity of
scotopic vision
(rods) and photopic
vision (cones) to
light intensity
not contribute to detailed central vision as the cones do. Both rod and cone photoreceptors
use graded voltage potentials to signal a change in light intensity. This is a change in the
membrane potential rather than an action potential.
Photoreceptors form synapses with two classes of neurons (bipolar and horizontal) in
the layers below, as shown in Figure 7-3. These also use graded voltage potentials, while
a third class of neurons in that layer, amacrine cells, generate action potentials. Both the
bipolar and amacrine cells form synapses with retinal ganglion cells (RGCs), the axons
of which form the nerve fiber layer that crosses the inner surface of the retina and runs
toward the optic nerve. These fibers are unmyelinated until they reach the optic disk.
The final layer of the retinal structure is the inner limiting membrane that separates
this nerve fiber layer from the vitreous humor.
