1.43. Peripheral Nervous System http://www.ck12.org
FIGURE 1.77
The blue lines in this drawing represent
nerves of the peripheral nervous system.
Every peripheral nerve is connected di-
rectly or indirectly to the spinal cord.The Sensory Division
Thesensory divisioncarries messages from sense organs and internal organs to the central nervous system. Human
beings have several senses. They include sight, hearing, balance, touch, taste, and smell. We have special sense
organs for each of these senses. What is the sense organ for sight? For hearing?
Sensory neurons in each sense organ receive stimuli, or messages from the environment that cause a response in the
body. For example, sensory neurons in the eyes send messages to the brain about light. Sensory neurons in the skin
send messages to the brain about touch. Our sense organs recognize sensations, but they don’t tell uswhatwe are
sensing. For example, when you breathe in chemicals given off by baking cookies, your nose does not tell you that
you are smelling cookies. That’s your brain’s job. The sense organs send messages about sights, smells, and other
stimuli to the brain (Figure1.79). The brain then reads the messages and tells you what they mean. A certain area