DO NOT EDIT--Changes must be made through “File info” CorrectionKey=B Nervous and CHAPTER 29 Endocrine Systems BIG IDEA The nervous system and the endocrine system are communication networks that allow all of the body systems to work together to maintain homeostasis. 29.1 How Organ Systems Communicate 10A, 11A 29.2 Neurons 4B, 10A, 10C, 11A 29.3 The Senses 10A, 11A 29.4 Central and Peripheral Nervous Systems 10A, 10C, 11A 29.5 Brain Function and Chemistry 11A Data Analysis CORRELATION OR CAUSATION? 2G 29.6 The Endocrine System and Hormones 4B, 10A, 10C, 11A ONLINE BIOLOGY HMDScience.com ONLINE Labs ■■ Investigating Eye Anatomy ■■ The Stroop Effect ■■ Video Lab Reaction Times ■■ QuickLab The Primary Sensory Cortex ■■ Video Lab Epinephrine and Heart Rate ■■ Reaction Time ■■ Brain-Based Disorders ■■ Smell and Olfactory Fatigue ■■ Investigating the Photic Sneeze Reflex (t) ©ISM/Phototake 834 Unit 9: Human Biology DO NOT EDIT--Changes must be made through “File info” CorrectionKey=B Q What happens when you think? Some technology allows researchers to look into the body of a living person. As recently as the 1970s, there was no way for doctors and scientists to see inside of the body without putting a patient through surgery. Today, researchers and others use magnets and computer technology, such as the MRI scan here, to study the internal organs of live patients. READING TOOLBOX This reading tool can help you learn the material in the following pages. USING LANGUAGE YOUR TURN Cause and Effect In biological processes, one step Identify the cause and the effect in the following sentences. leads to another step. When reading, you can often 1. Some hormones cause growth. So a person will be recognize these cause-and-effect relationships by words very tall if his or her body produces large amounts of that indicate a result, such as so, consequently, next, then, these hormones. and as a result. 2. Fear causes the production of adrenaline. As a result of the adrenaline, the heart beats faster and the body is prepared to run away. Chapter 29: Nervous and Endocrine Systems 835 DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A 29.1 How Organ Systems Communicate 10A, 11A KEY CONCEPT The nervous system and the endocrine system provide the means by which organ systems communicate. VOCABULARY MAIN IDEAS nervous system The body’s communication systems help maintain homeostasis. endocrine system The nervous and endocrine systems have different methods and stimulus rates of communication. central nervous system (CNS) peripheral nervous system (PNS) Connect to Your World Scientists try to find new ways, such as MRI scans, to study the brain, because the brain is so important. Your brain lets you think and move. It controls digestion, heart 10A describe the interactions that occur among rate, and body temperature. Your brain performs these functions with help from the systems that perform the functions rest of the nervous system and the endocrine system. of regulation, nutrient absorption, reproduction, and defense from injury or illness in animals and 11A describe the role of internal feedback mechanisms in the Main Idea 10A, 11A maintenance of homeostasis The body’s communication systems help maintain homeostasis. Homeostasis depends on the ability of different systems in your body to communicate with one another. To maintain homeostasis, messages must be generated, delivered, interpreted, and acted upon by your body. The nervous system and the endocrine system are the communication networks that allow you to respond to changes in your environment countless times each day. • The nervous system is a physically connected network of cells, tissues, and organs that controls thoughts, movements, and simpler life processes, such as swallowing. For example, when you walk outside without sunglasses on a sunny day, your nervous system senses the bright light coming into your eyes. It sends a message to signal your pupils to shrink and let in less light. • The endocrine system (EHN-duh-krihn) is a collection of physically disconnected organs that helps to control growth, development, and responses to your environment, such as body temperature. For example, when you are outside on a hot day or you exercise, your body starts to feel warm. Your endocrine system responds by initiating an internal feedback mechanism. In this case, negative feedback counteracts the increase in body temperature and the body begins to sweat more so that you can cool down to normal body temperature. Both of these systems, which are shown in figure 1.1, prompt you to re- spond to a stimulus in your environment and maintain homeostasis. A stimulus (STIHM-yuh-luhs) is defined most broadly as something that causes figure 1.1 The nervous system a response. In living systems, a stimulus is anything that triggers a change in (yellow) is a physically connected an organism. Changes can be chemical, cellular, or behavioral. network, while the endocrine sys- tem (red) is made up of physically Analyze What stimuli cause you to sweat and trigger your pupils to shrink? separated organs. 10A 836 Unit 9: Human Biology DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A Main Idea 10A The nervous and endocrine systems have different methods and rates of communication. Think about your endocrine system as working like a satellite television system. A satellite sends signals in all directions, but only televisions that have special receivers can get those signals. Your endocrine system’s chemical signals are carried by the bloodstream throughout the body, and only cells with certain receptors can receive the signals. Think of your nervous system being like cable television. A physical wire connects your television to the cable provider. Similarly, your nervous system sends its signals through a physical network of specialized tissues. The nervous and endocrine systems also communicate at different rates. Your endocrine system works slowly and controls processes that occur over long periods of time, such as hair growth, aging, and sleep patterns. The endocrine system also helps regulate homeostatic functions, such as body temperature and blood chemistry. For example, as the day gradually warms, your endocrine system responds by releasing chemicals that stimulate sweat glands. The change in the temperature over the course of a day is slow so you do not need a rapid response from your body. Your nervous system works quickly and controls immediate processes, spinal cord such as heart rate and breathing. If you touch your hand to a hot stove, an immediate response from the nervous system causes you to jerk your hand away. Without a quick reaction, your hand would be badly burned. Signals move from the skin on your hand to the muscles in your arm by nerves passing through the two parts of the nervous system: the central and the peripheral. The central nervous system (CNS) includes the brain and spinal cord. The CNS interprets messages from nerves in the body and stores some of these messages for later use. The peripheral nervous system (PNS) includes the cranial nerves and nerves of the neck, chest, lower back, and pelvis. It transmits figure 1.2 This medical illustra- tion shows how the spinal cord messages to the CNS, and from the CNS to organs in the body. You can see some connects the brain to the nerves of the nerves of the PNS in figure 1.2. that run throughout the body. Explain Which system controls the rate at which your fingernails grow? ©Anatomical Travelogue/Photo Researchers, Inc. Researchers, Travelogue/Photo ©Anatomical Self-check Online HMDScience.com 29.1 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. Explain why your body needs a 3. Explain How can an endocrine Cell Structure communication system. 10A system response be considered an 5. What structures on a cell 2. What are three differences internal feedback mechanism? membrane might ensure between the ways in which the 11A that the endocrine system’s endocrine system and the 4. Predict How might a clogged blood signals only affect the cells nervous system work? 10A vessel affect the nervous system’s for which they are intended? and the endocrine system’s abilities to deliver signals? 10A Chapter 29: Nervous and Endocrine Systems 837 DO NOT EDIT--Changes must be made through “File info” CorrectionKey=A 29.2 Neurons 4B, 10A, 10c, KEY CONCEPT The nervous system is composed of highly 11A specialized cells. VOCABULARY MAIN IDEAS neuron Neurons are highly specialized cells. dendrite Neurons receive and transmit signals. axon resting potential sodium-potassium pump Connect to Your World action potential When you eat a snack, you might flick crumbs off of your fingers without giving it synapse much thought. The specialized cells of your nervous system, however, are hard at terminal work carrying the messages between your fingers and your brain. neurotransmitter 4B investigate and explain cellular processes, including homeostasis, energy conversions, 10c transport of molecules, and Main Idea synthesis of new molecules; 10A describe the interactions that occur Neurons are highly specialized cells. among systems that perform the functions of regulation, nutrient A neuron is a specialized cell that stores information and carries messages absorption, reproduction, and defense from injury or illness in within the nervous system and between other body systems. Most neurons animals; 10c analyze the levels of have three main parts, as shown in figure 2.1. organization in biological systems and relate the levels to each other 1 The cell body is the part of the neuron that contains the nucleus and to the whole system; 11A describe the role of internal and organelles. feedback mechanisms in the 2 Dendrites are branchlike extensions of the cytoplasm and the cell mem- maintenance of homeostasis brane that receive messages from neighboring cells.