Lesson 3 consists of a single activity in which students investigate the opposing actions of muscles. In the Web version of the activity, students view an animation of a character running up to and then kicking a soccer ball. They then determine the order in which six muscle groups work to execute the kick. In the print version of the activity, students watch a classmate demonstrate a kicking motion and then determine the order in which the same six muscle groups contract. Students learn that muscles produce movement by contracting and that opposing muscles are required to move a limb in opposing directions.
After completing this lesson, students will be able to
See the following sections in Information about the Musculoskeletal and Skin Systems:
|1||Yes||Master 3.1, Muscles, 1 transparency
Master 3.2, Anatomy of a Kick Results, 1 copy per team of 3
Master 3.3, Relax! I’m Contracting, 1 copy per team of 3 and 1 transparency
Master 3.4, Muscle Group Sequence, 1 copy per team of 3 and 1 transparency (for print version only)
|None except photocopies and transparencies|
Reserve the required number of computers (one computer for each student team of three). To save time, have browsers open to this URL: http://science.education.nih.gov/supplements/bone/student.
Prepare photocopies and transparencies.
For classrooms using the Web-based version of this activity:
Note to teachers: The following procedure describes how to conduct the Web-based version of this activity, the preferred form of instruction. See instructions for conducting the alternative, print-based version.
Students should examine both the biceps and triceps. Some students may not know the names of these muscles. Point out to students that the biceps is on the top (or front) of the upper arm and the triceps is on the bottom (or back) of the upper arm.
Students generally can feel the biceps of the right arm shorten (contract) and become less soft and more firm as the arm is flexed. At this point, the triceps is relaxed. As the arm is extended, particularly if it is held straight out or straight down, students can feel the biceps stretch and become relaxed while the triceps becomes more firm (it is difficult to feel the triceps contract).
Students should recognize that the biceps flexes the arm while the triceps extends it. Some students might believe erroneously that the biceps pulls (contracts) to flex the arm and then pushes to extend it. However, they should have learned from their own muscles that the biceps is very relaxed and the triceps begins to tighten when the arm is extended.
Students should conclude that muscles act by contracting (shortening). Help them realize that muscles work in opposing pairs to produce opposite (for instance, push-pull) movements.
Note to teachers: The major objectives of this lesson are to stress that muscles produce movement when they contract and that they are arranged in opposing pairs. You should not get distracted with details of anatomy. Questions may come up, however, about how muscles attach to bone. You may wish to explain that
Students will probably understand that the biceps and triceps should each connect the upper arm to the lower arm. Although the anatomy is more complex than students need to understand, the biceps originates in two places, the collarbone and the upper arm bone (humerus) and then attaches to the radius of the lower arm. The triceps also originates in the collarbone and the humerus and then attaches to the ulna of the lower arm.
Point out to students that the human body has more than 660 skeletal muscles, which includes 56 total in both legs.
By noting specific points of attachment of the muscle groups, students can assess the movement that contraction of a muscle group produces about joints at the hip, knee, and ankle.
Give each team one copy of Master 3.2, Anatomy of a Kick Results.
Explain that they will use this handout to record the locations and movements produced by the six muscle groups involved in the activity.
Direct students to their computer stations.
After the opening animation plays, the activity screen is divided into three sections:
Students should do the following:
These animations show the leg movements used to kick a ball. Students can play the animations at normal speed or use the slider to control the animation manually.
The first muscle group to contract (D) is already entered on the screen. Students enter muscle groups functioning second through sixth during the kick. If the sequence entered is correct, an animation of the character kicking the ball plays. If a sequence entered is not correct, the boxes are cleared from the first incorrect box to the end. The contraction of muscle groups A and F occurs almost simultaneously during the kick. For this reason, students can either enter AF or FA within the sequence and be considered correct. Therefore, the correct sequences are D B F A C E and D B A F C E.
Tip from the field test: If students would like a larger view of the animations, they can right click with their mouse and use the zoom feature.
Student responses will vary. Bring out in the discussion that muscles attached to bones on both sides of a joint produce movement about the joint. Students should also recognize that by being arranged in opposing pairs, muscles, which can only contract, move bones back and forth.
Answers will vary. Focus student thinking on the many movements the human body is capable of performing. For example, the hand and fingers are capable of a wide variety of different movements.
Master 3.3 depicts a human skeleton in three panels. In the first panel, the skeleton has its arms extending straight out from the body. The second panel depicts movement about each elbow and wrist joint. In the third panel, the arms have returned to their original positions. In Panel A, eight muscles are shown. Each muscle attaches on either side of a joint and is identified by a number.
Students should mention the following:
Give students about five minutes to complete the task. The correct responses are shown in Figure 3.3.
Figure 3.3. Muscle movement about joints.
If a student makes a mistake, ask the class if they agree. Guide the discussion to bring out the correct muscle movements.
Students should notice that as movement goes from Panel A to Panel B, the pattern of muscle contraction is the opposite of that going from Panel B to Panel C. This is because the movement depicted in the panels goes from a starting position to a new position and then back to the original position.
The following is an example of what a student might write: “Opposing pairs of muscles contract to cause movement in opposite directions.”