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. 

Hair cells within the inner ear and olfactory cilia within the nasal passage both act as receptors of sensory information. Receptors trigger neural signals to be interpreted (i.e. perceived) by the brain. Even though hair cells in the inner ear vibrate to detect sound, smells are not sensed by olfactory cilia using the same mechanisms. As a part of the olfactory system, olfactory cilia are located within the nasal passage, not the inner ear. Neither hair cells nor olfactory cilia shrivel when exposed to sensory information. 

Unlike the other sensory systems, the skin is saturated with sensory receptors all over the body. There are places where nerves are more concentrated; however, there is no location where the sense of touch is centralized (i.e. it is sensed all over). On the other hand, the receptors for the auditory system are located in the cochlea, the gustatory receptors are located on the taste buds, and the olfactory system receptors are located within the upper portion of the nasal passage.

When the eardrum vibrates, it moves the tiny ossicles. The ossicles are three bones in the middle ear that are among the smallest bones in the human body. These bones serve to transmit sounds from the eardrum to the cochlea.