activity 22 Muscles and Movement BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN Grade 4 Quarter 3 Activity 22 SC.F.1.2.1 The student knows that the human body is made of systems with structures and functions that are related. SC.H.1.2.3 The student knows that to work collaboratively, all team members should be free to reach, explain, and justify their own individual conclusions. SC.H.1.2.5 The student knows that a model of something is different from the real thing, but can be used to learn something about the real thing. ACTIVITY ASSESSMENT OPPORTUNITIES The following suggestions are intended to help identify major concepts covered in the activity that may need extra reinforcement. The goal is to provide opportunities to assess student progress without creating the need for a separate, formal assessment session (or activity) for each of the 40 hands-on activities at this grade level. 1. Point out that, in this activity, students made a model to study how something in their body works. Models are good because they help us visualize how things work. But, sometimes they are not accurate. Have students make a list with two columns: label one column accurate, the other inaccurate. In the accurate column, students should write ways they think the model was good and helpful and accurately showed how arm muscles work. (The model helps show how flexor and extensor muscles work in opposition as our arm moves.) In the inaccurate column, have students list ways the model might be misleading. (Our bones are not hollow; muscles are not thin bands; muscles are made up of specialized cells, not rubber; there are two bones in the lower arm, not one; and so on.) 2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the activity. In addition to the above assessment suggestions, the questions in bold and tasks that students perform throughout the activity provide opportunities to identify areas that may require additional review before proceeding further with the activity. broward county hands-on science Quarter 3 263
264 activity 22 Muscles and Movement
activity 22 Muscles and Movement OBJECTIVES Students observe how muscles contract to make the body move. The students construct a model of the arm observe how muscles move bones SCHEDULE About 45 minutes VOCABULARY biceps extensor flexor muscle muscular system tendon triceps MATERIALS For each student 1 Activity Sheet 22 1 pair safety goggles* For each team of two 1 ball, table tennis 2 paper clips 1 pushpin 2 rubber bands, thin 1 ruler, metric 2 tubes, cardboard, large For the class 1 btl glue 1 roll tape, masking *provided by the teacher PREPARATION 1 2 3 You will need to glue the table tennis balls to the cardboard tubes at least 24 hours before conducting this activity. Obtain from the kit the container of glue and one tube and one table tennis ball for each team of two students. Place a small amount of glue around the rim at one end of each tube and set a ball on that end. The glue must be completely dry before the students conduct the activity. Make a copy of Activity Sheet 22 for each student. Each group of two students will need one tube with a ball glued to the end of it, one plain tube, two paper clips, two thin rubber bands, one pushpin, one metric ruler, and several pieces of masking tape. BACKGROUND INFORMATION Muscles are body tissues that are able to contract. There are three kinds of muscles in the human body: skeletal, smooth (found in some internal organs), and cardiac (found in the heart). This activity focuses on skeletal muscle. Skeletal muscle is striated, which means that alternating light and dark stripes can be seen when the muscle tissue is viewed under a microscope. We move skeletal muscles voluntarily, that is, these muscles are under our conscious control. Almost all skeletal muscles (with the exception of the tongue and the pharynx) are attached to bones by tendons. When skeletal muscles contract, they move the bones to which they are attached. A muscle that causes a body part to bend when it contracts is called a flexor. A muscle that causes a body part to extend or straighten out when it contracts is broward county hands-on science Quarter 3 265
called an extensor. Flexor muscles and extensor muscles work together to make our bodies move. In this activity, students will build a model of a human arm including the forearm and upper arm. By bending the model arm at the elbow and then straightening it out again, they will be able to observe the action of the biceps (a flexor muscle on the front of the upper arm) and the triceps (an extensor muscle on the back of the upper arm). Activity Sheet 22 Muscles and Movement 1. Label the contracted and relaxed muscles. contracted relaxed 1 2 Guiding the Activity Write the word muscle on the board. Tell students that muscle is body tissue that functions in movement. Remind students that bones support our bodies and protect vital organs. Then ask, What do muscles do? Write the words muscular system on the board. Tell students that movement in our bodies is the responsibility of the muscular system. The muscular system is made up of all the muscles in the body including muscles that move our limbs and heart. Tell students to feel their arm muscles as they bend and swing their arms. Ask, What do you think is happening to cause your arm to move? Tell students to watch the big muscle on the front of their upper arm as they hold their arm out straight, palm-up, and then bend it at the elbow. 266 activity 22 Muscles and Movement 2. Draw your model of the arm. Use the following labels: elbow, wrist, shoulder, extensor muscle, flexor muscle, biceps, and triceps. Drawings should be similar to Figure 22-2. Additional Information Students answers may include that muscles allow us to move our bodies and to lift, push, and pull things. Students will probably say that their muscles are allowing them to move their arms.
Guiding the Activity Ask, Did the shape of your upper arm muscle change? Did it get shorter or longer? Additional Information Yes. It got shorter. 3 4 Tell students that when a muscle contracts, it gets shorter (see Figure 22-1). Write the word tendon on the board. Tell students the tendons are the tissues that connect muscle to bone. Distribute Activity Sheet 22 and have the students complete question 1. Write the terms flexor and extensor on the board. Inform the students that a flexor is a muscle that bends a body part. An extensor is a muscle that straightens out a body part. Tell students to place one arm straight out in front of them, palm-up, on their desk. Ask, If you wanted to bend your arm at the elbow and lift your forearm and hand off the desk, would you use a flexor or an extensor muscle? Now ask, If you wanted to straighten out your bent arm, would you use a flexor or an extensor muscle? Tell students that they will construct a model of an arm (both the forearm and upper arm) from the step-by-step instructions you are about to give them. Distribute the needed materials to each team. Throughout the assembly phase, offer help as needed. Tell the teams to pick up the tube that has a ball glued to one end of it and use a pushpin to poke a hole in the tube 5 cm from the other end. Tell them to poke another hole directly opposite the first. Have them repeat this procedure with the tube that does not have a ball attached to it. relaxed contracted Figure 22-1. Muscle tissue, contracted and relaxed. A flexor muscle would be used to bend the arm. An extensor muscle would be used to straighten the arm. contracted broward county hands-on science Quarter 3 267
5 Guiding the Activity Next, tell them to straighten out a paper clip and push it through the two pin holes in the tube with the ball glued to it. With an equal length of paper clip protruding from each side of the tube, have them bend the ends of the paper clip toward the open end of the tube. Tell them to do the same to the other tube by pushing the straightened paper clip through the pin holes in the tube and bending the ends of the clip toward the short end of the tube. Using that same tube, instruct them to loop a separate rubber band over each bent end of the paper clip and tape the ends of the paper clip against the tube. Then have them place the tubes together so that the ball is in the middle and the paper clips are at opposite ends of the tubes. Tell them to carefully pull the rubber bands over the bent ends of the paper clip on the other tube and to tape the ends of that clip against the tube. When all of the teams have finished assembling, have them label their model (see Figure 22-2). Tell them to write elbow at the end of each tube closest to the ball, wrist at the open end of one tube, and shoulder at the open end of the other. shoulder elbow Figure 22-2. A model of the arm. 268 activity 22 Muscles and Movement biceps flexor muscle Additional Information It may be easier if one student holds the tubes together while his or her teammate extends the rubber bands and tapes the ends of the paper clips in place. Safety Note: Tell students to use caution when handling the rubber bands. triceps extensor muscle wrist
6 Guiding the Activity Next, have one student in each team hold the two tubes in a straight line while the other tapes the rubber band on one side of the tube near the elbow end of the forearm (wrist-to-elbow) tube. Additional Information 7 8 On the other side of the apparatus, have them separate the rubber band slightly and tape it to the ball. Have students bend the model arm to simulate what happens to the muscles of the arm when the arm bends at the elbow. Ask, Which rubber band represents the flexor muscle? Ask, When you bend the model arm, does the flexor get shorter or longer? Why? What kind of muscle is represented by the other rubber band? Is it longer or shorter when the model arm is bent? Why? Write the words biceps and triceps on the board. Tell students that the biceps is on the front and inside of the upper arm, and the triceps is on the back and outside of the upper arm. Begin a discussion by asking, Do you think your biceps is a flexor or an extensor muscle? Ask, Do you think your triceps is a flexor or an extensor muscle? Have students identify the biceps rubber band and the triceps rubber band on their model. Then write the word tendon on the board. Tell students that muscles are attached to bones by tendons. Ask, Which part of your model represents the tendons? Students should identify the section of rubber band that extends from shoulder to elbow on the inside of the model arm as the flexor muscle. It gets shorter because it is contracting. an extensor muscle It is longer because it is relaxed. Contracting (shortening) the extensor muscle would cause the bent arm to straighten. The biceps bends the arm. Therefore, it is a flexor muscle. 9 The triceps extends or straightens the arm. Therefore, it is an extensor muscle. Students should respond that the paper clips and tape represent tendons since they attach the rubber bands (muscles) to the cardboard tubes (bones). broward county hands-on science Quarter 3 269
Guiding the Activity Have students complete question 2 on their activity sheets. Additional Information A good place to look for muscle-tendon-bone interaction in the human body is the calf/achilles tendon/heel area. Have students feel their own Achilles tendon. Tell them that they also have tendons in their elbows. R EINFORCEMENT Tell students to place their fingertips on their cheeks just in front of their ears. Tell them to clench and unclench their teeth. They will feel their jaw muscles contracting and relaxing. SCIENCE JOURNALS Have students place their completed activity sheets in their science journals. 270 activity 22 Muscles and Movement C LEANUP The arm models may be disassembled. The rubber bands and tubes, half of which have a table tennis ball attached, may be returned to the kit. The paper clips and pieces of tape should be discarded.
Connections Science Challenge Have interested students research the smooth muscle of the human body. Their research should reveal answers to several questions: Is smooth muscle under our conscious control? What organs are made of or contain smooth muscle? What are the functions of these organs? Science Extension Have students do the following activity to discover what happens when muscles are overworked: Count how many times you can rapidly open and close a spring clothespin in 30 seconds, and record the results. (Each opening and closing should be counted as one action.) Without resting between trials, repeat the test four more times, and record the results for each trial. In a follow-up discussion, have students compare their results. What happened as trials were repeated? (Muscles began to tire, and the number of actions decreased.) Help students make a bar graph of class results, with the horizontal axis labeled Trial Number and the vertical axis labeled Number of Actions. Each bar will show the minimum and maximum number of actions for each trial. Science and the Arts Ask students to investigate the major types of joints in the human body and to identify specific examples of each type. Have volunteers use pictures cut from magazines or their own drawings to prepare a bulletinboard display illustrating the joint types and examples. Science and Careers Invite a physical therapist to visit the class to discuss the education and training required for such a career. Ask the visitor to describe various common disorders and injuries for which physical therapy is helpful and to explain the therapy process. If possible, arrange small-group field trips to a therapy center so the students can observe the therapy process. Science and Health Have students research why stretching and warm-up exercises are important before more strenuous exercise or physical activity. (If muscles and tendons are exercised strenuously when they are tight, injury is more likely to occur.) Science and Language Arts The Achilles tendon is named after Achilles, who, according to Greek mythology, was a great warrior who fought in the Trojan war. Encourage students to read the story of Achilles in the book The Iliad to discover how the Achilles tendon got its name. Science, Technology, and Society Encourage students to investigate devices and technologies that have been developed to aid people with orthopedic handicaps. As appropriate, encourage supervised use of the Internet for research projects related to the human body. A list of related websites is provided in the References and Resources section. broward county hands-on science Quarter 3 271
272 activity 22 Muscles and Movement