Objectives• Explain how the nervous and

endocrine systems help maintain homeostasis.

• Contrast the nervous and endocrine systems’ methods of communication.

Section ResourcesUnit Resource Book

Study Guide pp. 23–24Power Notes p. 25Reinforcement p. 26

Interactive Reader Chapter 29Spanish Study Guide pp. 289–290

Biology Toolkit pp. C9, D9

TechnologyPower Presentation 29.1Media Gallery DVDOnline Quiz 29.1

Activate Prior Knowledge Have students think of a sports team playing a big game. If the team wants to win, they have to run plays that will put them in the best scoring position. Ask, How are all the players going to know what play to run? The coach or player communicates the play to other team members. Tell students that the body has two major modes of internal communication, through the nervous and endocrine systems. The types of signals they send are very different.

FIGURE 29.1 Point out that the organs of the endocrine system are not physically connected. They communi-cate with the body by way of the chemical signals they produce that travel through the bloodstream.

AnswersA Analyze Elevated body tempera-

ture causes the body to sweat. Bright light causes the pupils to shrink.

Plan and PreparePlan and Prepare

TeachTeach

TEACH FROM VISUALSTEACH FROM VISUALS

FIGURE 29.1 The nervous system (yellow) is a physically connected network, while the endocrine sys-tem (red) is made up of physically separated organs.

How Organ Systems CommunicateKEY CONCEPT The nervous system and the endocrine system provide the means by which organ systems communicate.

MAIN IDEAS• The body’s communication systems help maintain

homeostasis.

• The nervous and endocrine systems have different methods and rates of communication.

VOCABULARYnervous system,nervous system, p. 874

endocrine system,endocrine system, p. 874

stimulus,stimulus, p. 874

central nervous system (CNS),central nervous system (CNS), p. 875

peripheral nervous system (PNS),peripheral nervous system (PNS), p. 875

29.1

Connect 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 rate, and body temperature. Your brain does these things with help from the endocrine system and the rest of the nervous system.

MAIN IDEA

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 systemnervous 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 that tells your pupils to shrink and let in less light.

• The endocrine systemendocrine 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 producing messages that tell your body to sweat more so that you can cool down.

Both of these systems, which are shown in FIGURE 29.1, let you respond to a stimulus in your environment and maintain homeostasis. A stimulusstimulus(STIHM-yuh-luhs) is defined most broadly as something that causes a re-sponse. In living systems, a stimulus is anything that triggers a change in an organism. Changes can be chemical, cellular, or behavioral.

Analyze What stimuli cause you to sweat and cause your pupils to shrink?

874 Unit 9: Human Biology

4.c Describe and differentiate among the organizational levels of organisms (e.g., cells, tissues, organs, systems, types of tissue).

b1b1b10hspe-092901.indd 8740hspe-092901.indd 8740hspe-092901.indd 874 9/9/09 7:49:13 PM9/9/09 7:49:13 PM9/9/09 7:49:13 PM

b10hspe-092901.indd 875b10hspe-092901.indd 875b10hspe-092901.indd 875

A

Differentiated Instruction

SECTION 29.1

BELOW LEVELEncourage students to write one or two potential test questions for each of the paragraphs that they read in this section. Tell them to write the answer to each question immediately. Explain that this is a method of reinforcing learning by building memory pathways by two different routes—reading and writing.

Biology Toolkit, QAR (Question-Answer Relationships), p. C9

ENGLISH LEARNERSSome students may not understand the analogy on page 875 comparing the endo-crine system to satellite television and the nervous system to cable television. You may need to explain the differences between standard, satellite, and cable television for students to grasp this concept.

Biology Toolkit, Analogies, p. D9

874 Unit 9: Human Biology

bbb111000hhhsssttteee---000999222999...iiinnndddddd 888777444b10hste-0929.indd 874b10hste-0929.indd 874b10hste-0929.indd 874 999///111000///000999 111:::555555:::333888 PPPMMM9/10/09 1:55:38 PM9/10/09 1:55:38 PM9/10/09 1:55:38 PM

00.2 ASSESSMENT

B

A

B

FIGURE 29.2 Have students refer to the photograph of the nervous system to distinguish the central and peripheral nervous systems. Ask

• Based upon the location of the structures, which one do you think belongs to the central nervous system? the spinal cord

• The peripheral nervous system? the nerves

VocabularyAcademic Vocabulary Two terms important to this chapter are central and peripheral. Students may be familiar with these words used in the context of computers. The computer is the central processing unit (CPU), which interprets and executes instructions. The peripher-als—scanners, printers, sound and video equipment—collect data as well as produce the desired end product.

AnswersA Infer endocrine system

Assess Use the Online Quiz or Section Quiz (Assessment Book, p. 571).Reteach Have students create a Venn diagram, comparing and contrasting the nervous and endocrine systems.

TEACH FROM VISUALSTEACH FROM VISUALS

Assess and ReteachAssess and Reteach

nervous system,endocrine system,stimulus,central nervous system (CNS),peripheral nervous system (PNS),

nervous system

endocrine system

stimulus

b1 6 PM

29.1 ASSESSMENT

Connecting CONCEPTS

ONLINE QUIZClassZone.com

FIGURE 29.2 This medical illustra-tion shows how the spinal cord connects the brain to the nerves that run throughout the body.

spinal cord

nerves

REVIEWING MAIN IDEAS

1. Why does your body need a communication system?

2. What are three differences between the ways in which the endocrine systemendocrine system and the nervous system nervous system work?

CRITICAL THINKING

3. Apply Which system, the endocrine or the nervous, controls the rate at which you blink? Explain.

4. Predict How might a clogged blood vessel affect the nervous system’s and the endocrine system’s abilities to deliver signals?

5. Cell Structure What structures on a cell membrane might ensure that the endocrine system’s signals only affect the cells for which they are intended?

MAIN IDEA

The nervous and endocrine systems have different methods and rates of communication.

You can think about your endocrine system as working like a satellite televi-sion 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. On the other hand, your nervous system is like cable television. A physical wire connects your television to the cable provider. Similarly, your nervous system sends its signals through a network of specialized tissues.

The nervous and endocrine systems also have different rates of commu-nication. 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, 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 passing through the two parts of the nervous system: the central and the peripheral. The central nervous system (CNS)central nervous system (CNS) includes the brain and spinal cord. The CNS interprets messages from other nerves in the body and stores some of these messages for later use. The peripheral nervous system (PNS)peripheral nervous system (PNS) is a network of nerves that transmits messages to the CNS and from the CNS to other organs in the body. You can see some of the nerves of the PNS extending from the spinal cord toward the neck and shoulders in FIGURE 29.2.

Infer Which system controls the rate at which your fingernails grow?

Chapter 29: Nervous and Endocrine Systems 875

b10hspe-092901.indd 875 9/2/08 1:48:59 PM

A

29.1 ASSESSMENT 1. A communication system allows the body

to respond to its environment and maintain homeostasis.

2. The nervous system sends signals through specialized tissues, works quickly, and controls immediate processes. The endo-crine system sends signals through the bloodstream, works slowly, and controls processes that occur over long periods of time.

3. The nervous system controls the rate of blinking because the nervous system controls fast processes.

4. A clogged blood vessel might slow the delivery of signals by the endocrine system but not by the nervous system.

5. Students’ responses should discuss mem-brane proteins such as gated channels, transport proteins, and protein receptors.

Chapter 29: Nervous and Endocrine Systems 875

b10hste-0929.indd 875b10hste-0929.indd 875 9/10/08 1:59:40 PM9/10/08 1:59:40 PM