Which of the following statements related to the "ON pathway" of the visual system is correct?
A)Bipolar cells fire action potentials only when bright light strikes the photoreceptors linked to them.
B)Bipolar cells spontaneously depolarize in the absence of input from photoreceptor cells.
C)Bipolar cells hyperpolarize in the absence of input from photoreceptor cells.
D)Glutamate receptors on bipolar cells are excitatory.
E)Only cones are associated with bipolar cells of the "ON pathway," rods are not.

Question

Which of the following statements related to the "ON pathway" of the visual system is correct?
A)Bipolar cells fire action potentials only when bright light strikes the photoreceptors linked to them.
B)Bipolar cells spontaneously depolarize in the absence of input from photoreceptor cells.
C)Bipolar cells hyperpolarize in the absence of input from photoreceptor cells.
D)Glutamate receptors on bipolar cells are excitatory.
E)Only cones are associated with bipolar cells of the "ON pathway," rods are not.

Quizplus · Accepted Answer

Bipolar cells in the retina do not fire action potentials like neurons in other parts of the nervous system; instead, they modulate their neurotransmitter release through graded changes in their membrane potential. In the dark, photoreceptors release glutamate, which in the case of ON bipolar cells, leads to their hyperpolarization due to the action of metabotropic glutamate receptors that decrease cation conductance. However, when light is present, it reduces the release of glutamate from photoreceptors, allowing ON bipolar cells to depolarize (not spontaneously, but due to a reduction in the inhibitory input from photoreceptors). This depolarization is contrary to the spontaneous depolarization mentioned in option B, indicating a misunderstanding in the explanation. The correct understanding is that ON bipolar cells are depolarized due to a decrease in glutamate release from photoreceptors in light, which is a key aspect of their function in the ON pathway of the visual system.

Which of the Following Statements Related to the "ON Pathway" of the Visual