Question

Photoreceptors are directly innervated by fibers of the optic nerve:

a. True

b. False

Answer 1

The optic nerve is the second cranial nerve concerned with vision. Optic nerve is developed from diencephalon. It is connected to the ganglion cells in the retina of the eye. The ganglion receives neural impulses from bipolar cells. The bipolar cells in turn receive signals from the photoreceptor rods and cones. The axons of the ganglion cells of the retina are converged to form the optic nerve, which the sends the signals to the vision center in the brain.

The rods and cones generate action potential due to rhodopsin pigment present when they are exposed to light (bright or dim light). These action potentials will generate signals that are then transmitted and received by the ganglionic cell layer which has the cell bodies. The nerve fibers contain the axons can be temporal and nasal fibers, which join at the optic disc. They form the orbital part of the optic nerve when they leave the eye posteriorly. Axons of the ganglion cells will then leave the optic nerve orbit via the orbital foramen. Thus, the optic nerve is not directly connected to the photoreceptor cells.

Right choice: b. false.