Hockenbury Discovering Psychology 5th txtbk

The Nervous System and the Endocrine System577. In the brain structurecalled the somatosensorycortex, the messages areconsciously interpretedas “PAIN IN THE HAND!”1. Skin receptors in thefingertips detect the electricshock, sending messages tosensory neurons.2. Sensory neuronscarry messages tothe spinal cord.6. The brain structure calledthe thalamus relays theincoming sensory informationto the appropriate corticalarea, where the signal isperceived as pain.3. Interneurons in thespinal cord relay messagesto motor neurons5. As the spinal reflex occurs,sensory neurons sendmessages up the spinalcord to the brain.4. Motor neurons sendmessages to hand muscles,causing a withdrawal reflexbefore the brain consciouslyregisters the sensation of pain.Cross sectionof spinal cordThe Peripheral Nervous SystemThe peripheral nervous system is the other major division of your nervous system.The word peripheral means “lying at the outer edges.” Thus, the peripheral nervoussystem comprises all the nerves outside the central nervous system that extendto the outermost borders of your body, including your skin. The communicationfunctions of the peripheral nervous system are handled by its two subdivisions: thesomatic nervous system and the autonomic nervous system.The somatic nervous system takes its name from the Greek word soma,which means “body.” It plays a key role in communication throughout the entirebody. First, the somatic nervous system communicates sensory informationreceived by sensory receptors along sensory nerves to the central nervous system.Second, it carries messages from the central nervous system along motornerves to perform voluntary muscle movements. All the different sensations thatyou’re experiencing right now are being communicated by your somatic nervoussystem to your spinal cord and on to your brain. When you perform a voluntaryaction, such as turning a page of this book, messages from the brain arecommunicated down the spinal cord, then out to the muscles via the somaticnervous system.The other subdivision of the peripheral nervous system is the autonomic nervoussystem. The word autonomic means “self-governing.” Thus, the autonomic nervoussystem regulates involuntary functions, such as heartbeat, blood pressure, breathing,and digestion. These processes occur with little or no conscious involvement. This isfortunate, because if you had to mentally command your heart to beat or yourstomach to digest the food you had for lunch, it would be difficult to focus yourattention on anything else.Figure 2.8 A Spinal Reflex A spinal reflexis a simple, involuntary behavior thatis processed in the spinal cord withoutbrain involvement. If you accidentallyshock yourself by using a metal fork to prya bagel out of a plugged-in toaster, you’llinstantly pull your hand away from thepainful stimulus—an example of the withdrawalreflex. The sequence shown belowillustrates how the withdrawal reflex canoccur before the brain processes the consciousperception of pain.peripheral nervous system(per-IF-er-ull) Division of the nervous systemthat includes all the nerves lying outside thecentral nervous system.somatic nervous systemSubdivision of the peripheral nervous systemthat communicates sensory information tothe central nervous system and carries motormessages from the central nervous systemto the muscles.autonomic nervous system(aw-toe-NOM-ick) Subdivision of the peripheralnervous system that regulates involuntaryfunctions.