Light will initially pass through the cornea and bend through the pupil to reach the lens. The lens is responsible for taking the refracted light and refocusing it. In doing so, the refocused rays will create an inverted image on the retina. This is accomplished through a process known as accommodation. The retina does not receive a complete image, but instead particles of light energy. Its receptor cells will take the light, translate it into neural impulses, and forward them to the brain where they will be reassembled right side up. 

The lens of the eye determines where the focus point will be in the rear chamber of the eye. When the lens is distorted, it can move the focus point slightly in front of or slightly behind the retina—back of the eye. When it is in front of the retina, it's called nearsightedness (e.g. a person can only see clearly when objects are near). When the focus point is behind the retina, it's called farsightedness (e.g. a person can only see clearly when objects are far away). Color blindness and macular degeneration do not have to do with where the focus point falls on the retina.

Rods allow us to see in black and white, and adapt much more than cones do when there is low light. In other words, they become even more sensitive in the dark. Cones are used for color vision and seeing in daylight. The fovea is a tiny spot in the center of the retina, but it contains only cones and allows for sharp visual acuity. The lens does not change depending on the lighting.

All light is received in the rear chamber of the eye on the retina. The place where the nerves exit the eye to go to the brain is also on the retina and it takes up some space. This creates a spot where we can't see anything: it is called a blind spot. Peripheral vision occurs when light is sensed that is not in the clearest part of our vision (e.g. not on the fovea), and can be observed when we see something "out of the corner of our eye.” Nearsightedness and farsightedness occur when the visual focus is a little in front of or a little behind the retina.

Humans have about 100 to 125 million rods in the retina, but only about 5 to 6.4 million cones. The fovea only contains cones—no rods. In the remainder of the retina, rods vastly outnumber cones.

The point at which the axons coming from each eye cross over and project to the opposite side of the brain is called the optic chiasm. The optic disk is the point at which the optic nerve exist the back of the eye to go into the brain. The lateral geniculate nucleus is an area in the brain positioned behind the optic chiasm (after the cross over takes place). The superior colliculus is even father behind the lateral geniculate nucleus and projects the image to the primary visual cortex.

The three bones are collectively known as ossicles. The ossicles transmit the vibrations of the eardrum further into the ear. The cochlea, eardrum, and pinna are all different parts of the ear and are not bones. 

Rods and cones convert sensory information (e.g. light) into neural signals. Hair cells serve the same purpose, but with sound. In other words, the hair cells convert sensory information (e.g. vibrations) into neural signals. Since rods and cones are located in the retina, the word that goes in the blank should be where hair cells are located. Hair cells are located in the cochlea. The pinna and eardrum are both possible locations, but they do not contain hair cells. 

The sense of taste is achieved through the taste buds on the tongue. Papillae are the little bumps on the tongue where taste buds cluster, but they are not actually involved in sensory processes. The teeth and gums have alternate functions and are not involved in the sensation.

There are five main sensory systems in the body relating to our senses. The olfactory system is the one that deals with smell. The gustatory system involves taste, the auditory system sound, and the nervous system involves all senses.