color absorption peak light capacity eurotransmitter outer segment
The Correct Answer and Explanation is:
Correct Answer:
The color absorption peak of photoreceptors is related to their light sensitivity and is influenced by neurotransmitter activity in the retina, specifically within the outer segment of the photoreceptor cells.
Explanation:
In the human retina, the outer segment of photoreceptor cells is where light absorption primarily occurs. Photoreceptors are divided into rods and cones. Rods are sensitive to low light levels and do not detect color, while cones are responsible for color vision and function best under bright light conditions.
There are three types of cone cells, each sensitive to a different range of wavelengths. These are commonly referred to as S-cones (short wavelengths), M-cones (medium wavelengths), and L-cones (long wavelengths). The absorption peak refers to the specific wavelength of light that each type of cone most effectively absorbs. S-cones peak at around 420 nanometers (violet to blue light), M-cones around 530 nanometers (green light), and L-cones near 560 nanometers (yellow to red light). Rods, which are not involved in color detection, have a peak sensitivity around 498 nanometers, which is in the blue-green part of the spectrum.
The outer segment of each photoreceptor contains stacks of membrane discs rich in a light-sensitive pigment known as opsin. When photons of light are absorbed by these pigments, a photochemical reaction occurs. This leads to a change in the shape of the opsin molecule, which ultimately affects the electrical state of the photoreceptor. This change causes the release of neurotransmitters at the synaptic end of the photoreceptor cell.
In darkness, photoreceptors continuously release the neurotransmitter glutamate. When light is absorbed, this release is reduced, which signals the presence of light to the bipolar and ganglion cells in the retina. These changes are then processed and transmitted to the brain through the optic nerve, allowing us to perceive color and light.
