1. The Senses System By Bryce Tappan

2. Mechanoreceptors Mechanoreceptors are neurons that create allow for ability to feel things. Sensory nerve endings detect changes of mechanical stimuli such as pressure, touch, sound, and muscular contractions. These changes are sent as messages to the brain through synapses. http://medical-dictionary.thefreedictionary.com/Mechanoreceptors http://en.wikipedia.org/wiki/Mechanoreceptor

3. Thermoreceptors Thermoreceptors are neurons that detect changes in temperature. They are used to feel changes in temperature that are moderate, while a separate neuron, nociceptors, feel changes in temperatures that could severely harm the body. Thermoreceptors help organisms adjust to their external environment as well as retain homeostasis. http://www.wisegeek.com/what-are-thermoreceptors.htm

4. Photoreceptors Photoreceptors detect light, or the absence of light, and send information back to the brain. This is what allows us to see. The two types of photoreceptors, light sensing and darkness sensing, become more active when the stimuli are increased. The two types are spread out through the retina in circular patterns; light sensing photoreceptors surround dark sensors and dark sensors surround light sensors creating what is called a receptive field. Each receptive field connects to cells that relay information to the brain to enable sight. http://www.nku.edu/~issues/illusions/Photorecepters.htm

5. Photoreceptors A Receptive Field shown below

6. Pain Receptors Also called nociceptors, pain receptors are found on nerve endings throughout the body. They activate in response to harmful stimulus to warn the body about possible damage. Once activated, they send neurotransmitters to the brain that convey the message of pain. http://www.wisegeek.com/what-are-pain-receptors.htm

7. Rhodopsin Rhodopsin is a biological pigment in the retina of the eye that creates photoreceptor cells and is necessary for the first steps of detecting light. It is extremely sensitive to light and absorbs green and blue wavelengths of light best, and it is what causes black and white vision in the dark. Rhodopsin is an photopsin, and the several different types of photopsins within the eye are what enable humans to see in color. http://en.wikipedia.org/wiki/Rhodopsin

8. Cell signaling Cells can communicate with one another in different ways. In some cases, direct contact with between cells allows them to exchange chemicals and to regulate metabolism. Other effects of direct contact include a change in shape. The shape of cells can be altered through contact and thus function is altered. Proteins that bind with certain cell receptors are another form of signaling between cells. Signaling cells synthesize signaling molecules that are received by receptors. Once received, the signaling molecule can cause the receptor to activate, deactivate, or differentiate. All of the above are methods cells use to communicate. http://www.ncbi.nlm.nih.gov/books/NBK21647/