Fine touch, vibration, proprioception and 2 points discrimination all utilizes the dorsal column pathway. The upper region utilizes the cuneate fasciculus in the spinal cord while the lower region depends on the gracile fasciculus. According to the passage, these sensations are of the rapid pathway whereas other sensations such as pain is not as fast. The dorsal column pathway is heavily myelinated while the pain pathway is not as myelinated.  

Patient A is unable to feel fine touch below the waist. A tumor in the gracile fasciculus region will prevent the signal from below the waist to reach the brain.  

Messages are picked up by sensory neurons in the peripheral nervous system and passed to interneurons in the central nervous system; responses are passed on to motor neurons in the peripheral nervous system

The fovea centralis, also known as the focal point, is the point where an image is centered when you stare at objects. This region of the retina has a high number of cone and rod cells, and explains why we can only clearly focus on one object at a time. Only the object lined up with the fovea centralis will remain clear, while peripheral objects appear blurry.

The cornea is avascular and made primarily of collagen, not lipids. When light first reflects off of a focused object, it strikes the eye on the cornea, where its high refractive index (1.4) allows most of the bending of light to occur at the interface between air and cornea. Unlike the lens, the cornea does not change its shape. The lens is tethered by suspensory ligaments, which are further connected to ciliary muscles. When the ciliary muscles contract, they release tension on the suspensory ligaments, thus making the lens more spherical and bringing the focal point closer to the lens. 

Rods and cones are two photoreceptors located on the back of the retina that are responsible for black, white (dark and light), and color sense. Rods are responsible for light and dark and are extremely sensitive, while cones sense color and are less sensitive.

The pupil and retina are both anatomical structures of the eye. The pupil controls the amount of light to pass through the eye, and the retina converts the electromagnetic signal to a neural stimulus.

The optic nerve collects stimuli from the retina and exits through the back of the eye to relay the information to the occipital lobe of the cerebrum. The point at which the optic nerve exits the eye contains no photoreceptors (rods and cones), and is unable to interpret light signals. This leads to a blind spot in the eye at the optic disk.

Rods and cones are the primary photoreceptors in our eyes. The rods are responsible for night vision, allowing us to differentiate different grays and blacks, whereas the cones are responsible for sensing color. Rods are concentrated in the periphery of the retina, making them essential for peripheral vision as well.

The retina contains both rods and cones and is responsible for converting electromagnetic stimulation to electrical impulses. These impulses are fired through the optic nerve to the occipital lobe for processing. The lens helps to focus light on the retina.

Rods and cones are the primary photoreceptors in our eyes. The rods are responsible for night vision, allowing us to differentiate different grays and blacks, whereas the cones are responsible for sensing color. There are three main pigments in cones, each perceiving one type of color: red, green, or blue. Deficiency in one type of cone can result in color blindness.

The retina contains both rods and cones and is responsible for converting electromagnetic stimulation to electrical impulses. These impulses are fired through the optic nerve to the occipital lobe for processing. The lens helps to focus light on the retina.

The two major photoreceptors of the body are cone cells and rod cells. Cone cells are most highly concentrated in the fovea and are best for color vision and visual acuity. In contrast, rod cells are found in higher concentrations away from the fovea (at the periphery of the retina) and used for seeing low levels of light and peripheral vision. Rod cells are therefore the photoreceptors used for night vision.

Ganglion cells and bipolar cells are also cells of the retina. They are used in the transmission of the electrical signals from the photoreceptors to the optic nerve and brain.