Question

The Pathways of Light and Visual Information

Select from the following terms to fill in the blanks in the passage below.

Use each term once.

bipolar cones cornea ganglion optic nerve

lens rods retina transduce optic chiasm

occipital pupil pattern photoreceptors

Light first passes through the _____________, a transparent covering of the eye, then through the _____________, the opening in the iris. Then the light passes through the _____________, which changes shape to focus the light so that it properly hits the retina. The light travels through the vitreous humor of the eye and then strikes the _____________, layers of cells in the back of the eye. The deepest layer of the retina is made of ____________, of which there are two types, _____________ concentrated in the center of the retina and responsible for visual experiences under normal viewing conditions and for color vision, and _____________ concentrated in the periphery of the retina and responsible for visual experiences in low levels of illumination.

The photoreceptors _____________ the light into a neural message that is sent to the ____________ cells (the next layer of cells in the retina) and then to the ____________ cells. The axons of the ganglion cells form the ____________ that exits the back of the eye and takes the visual information to the brain.

The two optic nerves meet at the ____________ where the inner axons from each nerve cross (decussate) to the opposite side of the brain. The outer axons remain on the same side of the brain. From the optic chiasm the axons travel to the thalamus. From the thalamus the information is sent to the primary visual cortex in the ____________ lobe and then to the association cortex for ____________ recognition and place recognition.

Answer 1

Answer

Light first passes through the cornea, a transparent covering of the eye, then through the pupil, the opening in the iris. Then the light passes through the lens, which changes shape to focus the light so that it properly hits the retina. The light travels through the vitreous humor of the eye and then strikes the retina, layers of cells in the back of the eye. The deepest layer of the retina is made of photoreceptors, of which there are two types, cones concentrated in the center of the retina and responsible for visual experiences under normal viewing conditions and for color vision, and rods concentrated in the periphery of the retina and responsible for visual experiences in low levels of illumination.

The photoreceptors transduce the light into a neural message that is sent to the bipolar cells  (the next layer of cells in the retina) and then to the ganglion cells. The axons of the ganglion cells form the optic nerve that exits the back of the eye and takes the visual information to the brain. The two optic nerves meet at the optic chiasm where the inner axons from each nerve cross (decussate) to the opposite side of the brain. The outer axons remain on the same side of the brain. From the optic chiasm, the axons travel to the thalamus. From the thalamus, the information is sent to the primary visual cortex in the occipital lobe and then to the association cortex for pattern recognition and place recognition.

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