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. 

The ossicles are the three smallest bones in the human body. They contain the anvil and transmit auditory perceptions to the cochlea. Within the cochlea, auditory receptors transmit these perceptions to sensory neurons and further to the brain. This is completed by transmitting sound from the air in the ossicles to the fluid within the cochlea. 

The five traditional taste sensations are sweet, sour, bitter, salty and umami. Spicy is a sensation that is combined with both taste and pain. This makes it a compound sensation and is untraditional in the way that a gustatory receptor would interpret this kind of taste. 

The absolute threshold is the minimum energy necessary for an individual to sense a given stimulus. This is not to be confused with the just-noticeable difference (JND), which defines the proportional amount of change in stimulus that can be perceived.

Focusing is accomplished by adjusting the thickness of the lens. This action is performed by the ciliary muscles. By changing the shape of the lens, light entering the eye from different focal points is brought into alignment on the retina, allowing for a clear image.

The pupils control the amount of light entering the eye, but do not contribute to focusing. Thus dilating or constricting the pupils has no effect on focus. Furthermore, these actions are outside of conscious control, while focusing may be performed consciously. 

The thickness of the cornea does not change under normal circumstances, and does not play a role in focusing. Likewise, the distance between the lens and the retina does not change under normal circumstances, and is not a movement performed by the eye.

While receptors for pain and temperature are indeed found throughout the body, their quantities are not uniform. In fact, they occur in varying quantities depending on the body part. This reflects the fact that different body regions have differing sensitivities to pain, touch, and temperature. The face for example, is far more sensitive than the legs or shoulders.

It is not true that some body parts possess neither pain nor temperature receptors, as all of the body is sensitive to these stimuli, merely to different extents. 

The hands are indeed sensitive to temperature, but aren't the body part most so.

The just noticeable difference is the minimum value in which a change in a sensory stimulus may still be detected. An example of this would be if an observer could tell the difference in the brightness in a room of 20 lit light-bulbs if 5 were dimmed at once, but not if fewer were.

Weber's law describes how changes in the just noticeable difference are proportional to changes in the magnitude of that stimulus. For example, to use the previous case of the room and light-bulbs, if the just noticeable difference in a room of 20 lights was five bulbs, then the just noticeable difference in a room of 40 illuminated light bulbs should be 10. They have increased by a factor of two.

The absolute threshold is the minimum value of a stimulus that is sufficient to be detected. This is different from the just noticeable difference in that it is not addressing changes in a stimulus, but merely the detection of that stimulus itself.

Accommodation describes the way in which the eyes will adjust to keep an object in focus depending on its proximity. This does not have to do with just noticeable changes in a stimulus.

The optic nerve leaves the eye through the blind spot, in the rear of the eye. The retina is interrupted in this region by the outflow of nerves carrying visual information to the brain. As such, it is devoid of photoreceptive cells, and no light is detected here. As a result of this, no visual information is generated by this region, and it is in effect, a blind spot.

The lens is the crystalline structure which focuses light entering the eye onto the retina, and is located in the front of the eye.

The cornea is the transparent layer forming the front of the eye. The sclera is the firm, white, outer layer of the eye.