1 the body’s 1 the body’ tran...

Section

1

The Body’sTransport System

Objectives

After this lesson, students will be able to

16.1.1

Explain the functions of the cardiovascular system.

16.1.2

Describe the function and structure of the heart.

16.1.3

Sequence the path taken by blood through the cardiovascular system.

16.1.4

Describe the functions and structures of arteries, capillaries, and veins.

Target Reading Skill

Sequencing

Explain that organizing information from beginning to end helps students understand a step-by-step process.

Answers

Bottom oval: Left side of heart; left oval: Body

Teaching Resources, Unit 3

•

Transparency LS155

Preteach

Build Background Knowledge

Transportation Systems

Display a map of a subway, bus, train, or local highway system. Ask:

What is the function of this transportation system?

(To pick up and deliver passengers at various points along a route)

Tell students that the cardiovascular system transports blood and other materials through the body in the same way. They will learn how in this chapter.

L1

Skills Focus

Inferring

Materials

newspapers, paper towels, two large plastic containers, cup with capacity of about 60 mL, watch or clock with a second hand

Time

20 minutes

Tips

Set up with newspapers, towels, or other materials for quick cleanup. Put large plastic containers in a

larger container to catch spills. Advise students to wear aprons. Consider doing this activity outdoors.

Expected Outcome

Results will vary. Students probably cannot make 75 transfers of water.

Think It Over

The heart is very strong to be able to pump continuously and at the speed it does.

1 The Body’s Transport System

How Hard Does Your Heart Work?1. Every minute, your heart beats about 75 to 85 times. With

each beat, it pumps about 60 milliliters of blood. Can you work as hard and fast as your heart does?

2. Cover a table or desk with newspapers. Place two large plastic containers side by side on the newspapers. Fill one with 2.5 liters of water, which is about the volume of blood that your heart pumps in 30 seconds. Leave the other container empty.

3. With a plastic cup that holds about 60 milliliters, transfer water as quickly as possible into the empty container,

trying not to spill any. CAUTION: Wipe up spills on the floor immediately. Have a partner time you for 30 seconds. As you work, count how many transfers you make in 30 seconds.

4. Multiply your results by 2 to find the number of transfers in 1 minute.

Think It OverInferring Compare your performance with the number of times your heart beats every minute. What do your results tell you about the strength and speed of a heartbeat?

Reading PreviewKey Concepts• What are the functions of the

cardiovascular system?

• What is the function and structure of the heart?

• What path does blood take through the cardiovascular system?

• What are the functions and structures of arteries, capillaries, and veins?

Key Terms• cardiovascular system • heart • atrium • pacemaker • ventricle • valve • artery • capillary • vein • aorta • coronary artery • pulse • diffusion • blood pressure

Target Reading SkillSequencing As you read, make a cycle diagram like the one below that shows the path that blood follows as it circulates throughout the body. Write each step of the pathway in a separate circle.

Late at night, a truck rolls through the darkness. Loaded withfresh fruits and vegetables, the truck is headed for a city super-market. The driver steers off the interstate and onto a smallerhighway. Finally, after driving through narrow city streets, thetruck reaches its destination. As dawn breaks, store workersunload the cargo. At the same time, a garbage truck removesyesterday’s trash and drives off down the road.

The Cardiovascular SystemLike the roads that link all parts of the country, your body hasa “highway” network, called the cardiovascular system, thatlinks all parts of your body. The cardiovascular system, alsocalled the circulatory system, consists of the heart, blood ves-sels, and blood. The cardiovascular system carries neededsubstances to cells and carries waste products away fromcells. In addition, blood contains cells that fight disease.

Right sideof heart

Lungs

Pathway of Blood

L1

SX05_TE_(LEP_L16)D3.fm Page 534 Wednesday, December 1, 2004 10:41 AM

AutoPage

Line

Instruct

The Cardiovascular System

Help Students Read

Previewing Visuals

Before students read, have them look at the images in this section and predict what they are about to read. The arrows in the visuals might suggest that they will be learning about pathways and the direction of blood flow in the body.

Teach Key Concepts

System Functions

Focus

Remind students that the cardiovascular system removes as well as delivers materials.

Teach

Ask:

What materials does the cardiovascular system deliver throughout the body?

(Oxygen and glucose)

How does the cardiovascular system get rid of carbon dioxide?

(Carbon dioxide is passed from cells into the blood, and then carried to the lungs, where it is exhaled.)

Refer students to Figure 1. Ask:

Why do you think the lungs have a dense network of blood vessels?

(The lungs are the only place where the exchange of gases between the body and the environment occurs, so many blood vessels must be in the lungs to do this work quickly and efficiently.)

Apply

Display two 2-liter bottles and one 1-liter bottle, or an equivalent capacity in other containers. Tell students that an adult of average size has 5 liters of blood circulating at any one time—an amount that would fill the containers.

learning modality: visual


•

Transparency LS156

Independent PracticeTeaching Resources, Unit 3

•

Guided Reading and Study Worksheet:

The Body’s Transport System

Student Edition on Audio CD

L1

L2

L2

Monitor Progress L2

Answers

Figure 1

Needed materials: oxygen and glucose; waste product: carbon dioxide

It transports cells that attack disease-causing microorganisms.

Heart

Blood vesselsin lungs

Key

Oxygen-rich blood

Oxygen-poor blood*

*Note: Blood is not actually blue in color.

FIGURE 1The Cardiovascular System The blood vessels of the cardiovascular system reach throughout the entire body. Blood flows through these vessels to every organ in the body. Classifying Name one needed material and one waste product transported by the cardiovascular system.

Delivering Needed Materials Most substances that needto get from one part of the body to another are carried byblood. For example, blood carries oxygen from your lungs toyour other body cells. Blood also transports the glucose yourcells use to produce energy.

Removing Waste Products The cardiovascular system picksup wastes from cells. For example, when cells break down glucose,they produce carbon dioxide as a waste product. The carbon diox-ide passes from the cells into the blood. The cardiovascular systemthen carries carbon dioxide to the lungs, where it is exhaled.

Fighting Disease The cardiovascular system also transportscells that attack disease-causing microorganisms. This processcan help keep you from becoming sick. If you do get sick, thesedisease-fighting blood cells will kill the microorganisms and helpyou get well.

How does the cardiovascular system help fight disease?


AutoPage

Line

AutoPage

Line

AutoPage

Line

Differentiated Instruction

English Learners/Beginning

Vocabulary: Link to Visual

Refer students to Figure 2, and point out the parts of the heart as you read the captions. Make sure students understand that

right

and

left

are correct, and that the diagram is positioned as if looking at another person. Distribute an unlabeled diagram and have students label and color in the right and left atria and ventricles.


L1

English Learners/Intermediate

Vocabulary: Link to Visual

Have students do the beginning-level activity. Then pair students with English-proficient students to write four sentences describing the functions of the right and left atria and ventricles in their own words.

learning modality: verbal

L2

The Heart

For:

The Heart Activity

Visit:

PHSchool.com

Web Code:

cep-4031

Students learn the parts of the heart and see the flow of blood through the heart.

Teach Key Concepts

The Heart

Focus

Refer students to Figures 2 and 3.

Teach

Ask volunteers to read the descriptions of the parts of the heart in Figure 2. Explain that the human heart has four chambers. Ask:

What are the four chambers of the heart?

(Right atrium, right ventricle, left atrium, left ventricle)

Ask:

Which chambers contain oxygen-rich blood?

(The left atrium and left ventricle)

Explain that the valves separate the chambers from each other and from other parts of the body. Valves are located between the left atrium and the left ventricle, the right atrium and the right ventricle, and the right ventricle and the artery to the lungs. Have students look at Figure 3. Then ask:

Where in Figure 2 is this valve shown?

(Between the right ventricle and the artery to the lungs)

Show the transparency of Figure 2 and have individual students state each step in the flow of blood through the heart while you trace it with a pencil eraser or other object.

Apply

Point out that the walls of the ventricles are much thicker than the walls of the atria. Ask:

How could having thick walls benefit the ventricles?

(Thick walls give ventricles the muscular strength to pump blood out of the heart.)

Extend

The Active Art will show students how the heart pumps.



•

Transparency LS157

L2

Right AtriumThe right atrium receives blood from the body that is low in oxygen and high in carbon dioxide.

Right VentricleThe right ventricle pumps oxygen-poor blood to the lungs.

SeptumThe septum prevents oxygen-rich and oxygen-poor blood from mixing in the heart.

AortaThe aorta carries blood from the left ventricle to the body.

Left AtriumOxygen-rich blood moves from the lungs into the left atrium.

Left VentricleThe left ventricle pumps oxygen-rich blood to all parts of the body.

Artery from heart to lungs

Major vein from lower body to heart

Major vein from upper body to heart

The HeartWithout the heart, blood wouldn’t go anywhere. The heart is ahollow, muscular organ that pumps blood throughout thebody. Each time the heart beats, it pushes blood through theblood vessels of the cardiovascular system.

Your heart, shown in Figure 2, is about the size of your fist.It is located in the center of your chest. The heart lies behindthe sternum (breastbone) and inside the rib cage. It is made ofcardiac muscle, which can contract over and over without get-ting tired.

For: The Heart activity Visit: PHSchool.comWeb Code: cep-4031

FIGURE 2

The HeartEvery second of your life, your heart pumps blood through your body. In a year, the heart pumps enough blood to fill more than 30 competition-size swimming pools.


http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cep&wcsuffix=4031

AutoPage

Line


Observing Your Heartbeat

Materials

stethoscope

Time

15 minutes

Focus

Explain that you can use a stethoscope to hear the sound of heart valves closing.

Teach

Have students use the stethoscope to listen to their own heartbeats. (After each use, use rubbing alcohol to clean the parts of the stethoscope that are inserted into the ears.) Ask:

What sounds do you hear as your heart beats?

(There is a deeper sound, “lub,” and a higher sound, “dup.”)

Apply

Ask:

How do the sounds of the heartbeat relate to the muscle contractions in the heart?

(The “lub” sound comes from the closing of the valves between the atria and ventricles, while the “dup” sound comes from the closing of the valves between the ventricles and the blood vessels.)

learning modality: kinesthetic

Circulation

Show the Video Field Trip to let students experience the intense exercise regimens of top athletes and understand how the training helps to improve the efficiency of the cardiovascular system. Discussion question:

How does the circulatory system get rid of carbon dioxide waste in the blood?

(The blood carries the carbon dioxide from the cells to the lungs, where it is exhaled into the air.)

L2

Special Needs

Model Heart

Have students examine a model heart with removable parts. Invite students to hold each part of the heart as you describe its function. Point out the difference in the size of the chambers and the thickness of the walls. Have students describe the different sizes of the blood

L1

vessels that lead in and out of the chambers. Give each student a beanbag or small, soft ball. Demonstrate how to squeeze the item at a steady rate to approximate 80 beats per minute, then have them do it. Emphasize that the heart works continuously like this for a person’s lifetime.

learning modality: kinesthetic

Monitor Progress L2

Drawing

Have students draw a heart, label its chambers, and write brief captions describing the function of each chamber. Have students place their drawings in their portfolios.

Answer

Figure 3

Valves prevent blood from flowing backward.

FIGURE 3Open and Closed Heart Valves As blood flows out of the heart and toward the lungs, it passes through a valve like the one in the photograph. Applying Concepts What is the function of a closed heart valve?

Open Valve Closed Valve

The Heart’s Structure The heart has a right side and a leftside. The right side of the heart is completely separated fromthe left side by a wall of tissue called the septum. Each sidehas two compartments, or chambers—an upper chamber anda lower chamber. Each of the two upper chambers, called anatrium (AY tree um) (plural atria), receives blood that comesinto the heart. Located in the right atrium is a group of heartcells called the pacemaker, which sends out signals that makethe heart muscle contract.

Each lower chamber, called a ventricle, pumps blood out ofthe heart. The atria are separated from the ventricles by valves.A valve is a flap of tissue that prevents blood from flowingbackward. Valves are also located between the ventricles and thelarge blood vessels that carry blood away from the heart.

How the Heart Works The action of the heart has two mainphases. In one phase, the heart muscle relaxes and the heart fillswith blood. In the other phase, the heart muscle contracts andpumps blood forward. A heartbeat, which sounds somethinglike lub-dup, can be heard during the pumping phase.

When the heart muscle relaxes, blood flows into the cham-bers. Then, the atria contract, squeezing blood out of the atria,through the valves, and into the ventricles. Next, the ventriclescontract. This contraction closes the valves between the atriaand ventricles, making the lub sound and squeezing blood intolarge blood vessels. As the valves between the ventricles and theblood vessels snap shut, they make the dup sound.

When muscle cells in the ventricles contract, they exert aforce on the blood. A force is a push or a pull. The force exertedby the ventricles pushes blood out of your heart and into arter-ies. The contraction of the left ventricle exerts much moreforce than the contraction of the right ventricle.

What is the role of the pacemaker?

Video PreviewVideo Field TripVideo Assessment

Circulation


Interpreting Pulse Data

Materials

watch with a second hand

Time

10 minutes each day over one week

Focus

Remind students that heart rate changes with changing oxygen needs.

Teach

Show students how to locate their pulse by placing the index finger of one hand on the other wrist at the base of the thumb and moving the fingers slightly until the pulse is felt. Explain that the pulse is caused by a spurt of blood passing through an artery. By measuring their pulse, students can measure their heart rate. Have them count the number of beats in the pulse for exactly one minute, and allow time for practice. Then direct students to take their pulse three times a day for one school week—when they wake up in the morning, after exercising, before going to bed—and record their pulse rates in data tables.

CAUTION:

Advise students not to exercise if they have a medical condition that rules out vigorous exercise.

At the end of the week, ask students to look for patterns in their data.

Apply

Ask:

How does your heart rate at certain times of the day or during certain activities relate to your body’s need for oxygen at that time?

(The heart rate increases when there is a high demand for oxygen.)

learning modality: logical/mathematical

Two Loops

Teach Key Concepts

Following the Two-Looped Path

Focus

Refer students to Figure 5.

Teach

Have students place a finger on the right atrium and follow the arrows to trace the path of blood as you read the passage. Then ask:

What is the difference between arteries and veins?

(Arteries carry blood away from the heart; veins carry blood to the heart.)

What are the two loops of blood flow?

(Heart to the lungs and back to the heart; heart to the body and back to the heart)

Apply Ask: When blood is pumped to the body cells, is it oxygen-rich? (Yes; it has just come from the lungs where it released carbon dioxide and picked up oxygen.) learning modality: visual

L3

L2

Skills Focus Creating data tables

Materials paper and pencil

Time 15 minutes

Tips Suggest that students’ tables contain a column for volume of blood per minute at rest and volume of blood per minute during vigorous exercise.

Expected Outcome The skeletal muscles need extra oxygen and glucose during exercise, so the amount of blood flowing to other organs is adjusted.

Extend Have students graph the data. learning modality: logical/mathematical

Two LoopsAfter leaving the heart, blood travels in blood vessels throughthe body. Your body has three kinds of blood vessels—arteries,capillaries, and veins. Arteries are blood vessels that carryblood away from the heart. From the arteries, blood flows intotiny, narrow vessels called capillaries. In the capillaries, sub-stances are exchanged between the blood and body cells. Fromcapillaries, blood flows into veins, blood vessels that carryblood back to the heart.

Pattern of Blood Flow The overall pattern of blood flowthrough the body is something like a figure eight. The heart isat the center where the two loops cross. In the first loop,blood travels from the heart to the lungs and then back to theheart. In the second loop, blood is pumped from the heartthroughout the body and then returns again to the heart.The heart is really two pumps, one on the right and one onthe left. The right side pumps blood to the lungs, and the leftside pumps blood to the rest of the body.

Blood travels in only one direction. If you were a drop ofblood, you could start at any point and eventually return to thesame point. The entire trip would take less than a minute. Asyou read about the path that blood takes through the cardio-vascular system, trace the path in Figure 5.

Loop One: To the Lungs and Back When blood from thebody flows into the right atrium, it contains little oxygen but alot of carbon dioxide. This oxygen-poor blood is dark red. Theblood then flows from the right atrium into the right ventricle.Then, the ventricle pumps the oxygen-poor blood into thearteries that lead to the lungs.

FIGURE 4Getting Blood to Body Cells During strenuous exercise, such as swimming, the pattern of blood flow through the body ensures that body cells get the oxygen they need quickly and efficiently.

Creating Data TablesScientists measured the vol-ume of blood that different organs receive, at rest and during vigorous exercise.

• At rest, the organs of the abdomen received about 1,400 mL of blood per minute (mL/min). During vigorous exercise, they received 600 mL/min.

• At rest, skeletal muscles received 1,200 mL/min. During vigorous exercise, they received about 12,500 mL/min.

• At rest, the kidneys received 1,100 mL/min. During vigorous exercise, they received about 600 mL/min.

Create a table to record these data. Then, use the data to explain why some organs receive more blood during exercise than others.

L1

SX05_TE_(LEP_L16)D3.fm 38 Wednesday, December 1, 2004 10:41 AM



• Transparency LS158

Address Misconceptions

The Color of BloodFocus Some students may think that some blood is actually blue.

Teach Tell students that oxygen-poor blood is dark red, not blue. Illustrations of the cardiovascular system often show vessels in blue and red to distinguish vessels that carry oxygen-rich blood from those that carry oxygen-poor blood. Ask: Why is some blood dark red? (It contains little oxygen.) Where does it change to bright red? (In the lungs; wastes move from blood to the air, while oxygen in air moves into blood. Blood that is rich in oxygen is bright red.)

Apply Ask: Why is blood in the veins traveling from the body to the right atrium dark red? (Body cells use up the oxygen in the blood and add wastes, so the blood in these veins would be low in oxygen and high in wastes—dark red.) learning modality: verbal

L1

Gifted and TalentedResearching Pacemakers Explain to students that in the case of disease or accident where a person’s pacemaker becomes damaged, an artificial pacemaker can be implanted beneath the skin and connected to the heart by wires. Tiny electrical impulses travel from the battery through the wires, and make the heart contract. Have students research artificial

L1 pacemakers that are sensitive to changes in body temperature and oxygen needs. Ask: Why would these be more efficient than pacemakers that do not have these functions? (They could match the person’s heart rate with his or her activity level.) Have students present their findings in a poster or visual presentation to the class. learning modality: visual

Monitor Progress L2

Skills Check Have students make flowcharts of the path of blood from one point until it reaches the same point again.

AnswerFigure 5 The lungs

Arteries to lungs

Rightatrium

Leftatrium

Veins fromlungs

Rightventricle

Leftventricle

Loop One

Loop Two

Arteries to body

Veins from body

Loop One:to the lungs and back to the heart

Loop Two:to the bodyand back to the heart

As blood flows through the lungs, large blood vessels branchinto smaller ones. Eventually, blood flows through tiny capillar-ies that are in close contact with the air that comes into thelungs. The air in the lungs has more oxygen than the blood inthe capillaries, so oxygen moves from the lungs into the blood.For the same reason, carbon dioxide moves in the oppositedirection—from the blood into the lungs. As the blood leavesthe lungs, it is now rich in oxygen and poor in carbon dioxide.This blood, which is bright red, flows to the left side of the heartand will be pumped through the second loop.

Loop Two: To the Body and Back The second loop beginsas the left atrium fills with oxygen-rich blood coming from thelungs. The blood then moves into the left ventricle. From the leftventricle, the blood is pumped into the aorta (ay AWR tuh), thelargest artery in the body.

Eventually, after passing through branching arteries, bloodflows through tiny capillaries in different parts of your body,such as your brain, liver, and legs. These vessels are in close con-tact with body cells. Oxygen moves out of the blood and intothe body cells. At the same time, carbon dioxide passes from thebody cells and into the blood. This blood, which is low in oxy-gen, then flows back to the right atrium of the heart throughveins, completing the second loop.

FIGURE 5Direction of Blood Flow Blood circulates through the body in two loops, with the heart at the center. Loop one goes from the heart to the lungs and back. Loop two circulates blood throughout the rest of the body. Interpreting Diagrams Where does the blood that enters the left atrium come from?

L3


AutoPage

Line

Arteries

Teach Key ConceptsFunctions of ArteriesFocus Remind students that arteries carry blood away from the heart.

Teach Explain that the heart itself must receive oxygen-rich blood to function. Ask: How does it get this blood? (Coronary arteries supply blood to the heart.) Sketch a cross-section of an artery. Ask: How does the structure of an artery relate to its function? (The smooth inner layer helps blood to flow freely. The muscular middle layer expands and relaxes in response to the heart pumping. The outer connective tissue makes the artery strong yet flexible.) What are you feeling when you take a pulse? (A spurt of blood pushing the artery walls and making them expand)

Apply Refer students to Figure 6. Ask: What is the main difference between the structure of arteries and veins, and why is this? (Arteries are thicker because the force of blood pumped through these vessels is stronger than the force flowing through the veins.) learning modality: visual

Math Skill Calculating a rate

Focus Tell students that the units of pulse rate are heartbeats per minute.

Teach Explain that people often calculate heart rate by counting the pulse for 10, 15, or 30 seconds and then multiplying.

Answer68 beats per minute

L2

Capillary

Artery

Single layer ofepithelial cells

Layer of epithelial cells

Connective tissue

Smooth muscle

ArteriesWhen blood leaves the heart, it travels through arteries. Theright ventricle pumps blood into the arteries that go to thelungs. The left ventricle pumps blood into the aorta. Smallerarteries branch off the aorta. The first branches, called thecoronary arteries, carry blood to the heart itself. Otherbranches carry blood to the brain, intestines, and other organs.Each artery branches into smaller and smaller arteries.

Artery Structure The walls of arteries are generally verythick. In fact, artery walls consist of three cell layers. Theinnermost layer, which is made up of epithelial cells, is smooth.This smooth surface enables blood to flow freely. The middlelayer consists mostly of muscle tissue. The outer wall is made upof flexible connective tissue. Because of this layered structure,arteries have both strength and flexibility. Arteries are able towithstand the enormous pressure of blood as it is pumped bythe heart and to expand and relax between heart beats.

Pulse If you lightly touch the inside of your wrist, you canfeel the artery in your wrist rise and fall repeatedly. This pulseis caused by the alternating expansion and relaxation of theartery wall. Every time the heart’s ventricles contract, they senda spurt of blood out through all the arteries in your body. Asthis spurt travels through the arteries, it pushes the artery wallsand makes them expand. After the spurt passes, the artery wallsrelax and become narrower again.

When you count the number of times an artery pulsesbeneath your fingers, you are counting heartbeats. By taking yourpulse rate, you can determine how fast your heart is beating.

FIGURE 6Artery, Capillary, and Vein The walls of arteries and veins have three layers. The walls of capillaries are only one cell thick. Relating Cause and Effect How does material get from inside capillaries to body cells?

The artery wall appears as a thick pink band surrounding a clump of red blood cells.

�



Capillaries

Teach Key ConceptsFunction of CapillariesFocus Refer students to Figure 6.

Teach Ask: Why are capillary walls so thin? (Materials must be able to pass easily between them and body cells.)

Apply Tell students that blood cells must pass through capillaries in single file. learning modality: visual


• Transparency LS159

Observing Diffusion

Materials 2 beakers, food coloring, salt, teaspoon

Time 10 minutes over two days

Focus Review the process of diffusion.

Teach Pour water into a beaker until it is one-third full. Add one-half teaspoon of salt and a few drops of food coloring. Stir until you have a uniform solution. Pour water into a second beaker until it is one-half full. Next, carefully pour the contents of the first beaker into the second. The salt water will sink to the bottom. Let the beaker stand overnight. The liquid will be uniformly colored.

Apply Ask: How is this process like diffusion in capillaries? (The concentration of salt in the salt water was higher than that in the fresh water; thus, the salt water diffused into the fresh. Glucose is higher in concentration in blood than in body cells, so it moves from the blood to body cells.) learning modality: visual

L1

Less Proficient ReadersIllustrating Blood Vessels Have students draw each type of blood vessel. The drawing should include leader lines labeling any parts discussed in the text and captions describing the functions of each type of vessel. Pair students with more proficient readers to read the

L1 corresponding text and to identify information to include in the drawings. Students can copy and expand upon the illustrations in the text or their own charts. Encourage students to use different-colored markers to distinguish structures. learning modality: visual

Monitor Progress L2

Writing Ask students to explain the differences between arteries and capillaries.

AnswersFigure 6 By diffusion

Alternating expansion and relaxation of the artery wall

Vein

Layer of epithelial cells

Smooth muscle

Connective tissue

Regulating Blood Flow The layer of muscle in an arteryacts as a control gate, adjusting the amount of blood sent todifferent organs. When the muscle contracts, the opening inthe artery becomes smaller. When the muscle relaxes, theopening becomes larger. For example, after you eat, your stom-ach and intestines need a greater blood supply for digestion.The arteries leading to those organs open wider, and moreblood flows through them. In contrast, when you are running,your stomach and intestines need less blood than the musclesin your legs. The arteries leading to the digestive organsbecome narrower, decreasing the blood flow to these organs.

What causes your pulse?

CapillariesEventually, blood flows from small arteries into the tiny capil-laries. In the capillaries, materials are exchanged between theblood and the body’s cells. Capillary walls are only one cellthick. Thus, materials can pass easily through them. Materialssuch as oxygen and glucose pass from the blood, through thecapillary walls, to the cells. Cellular waste products travel in theopposite direction—from cells, through the capillary walls,and into the blood.

One way that materials are exchanged between the bloodand body cells is by diffusion. Diffusion is the process bywhich molecules move from an area of higher concentration toan area of lower concentration. For example, glucose is morehighly concentrated in the blood than it is in the body cells.Therefore, glucose diffuses from the blood into the body cells.

Calculating a Rate A rate is the speed at which something happens. When you calculate a rate, you compare the number of events with the time period in which they occur. Here’s how to calculate the pulse rate of a person whose heart beats 142 times in 2 minutes.

1. Write the comparison as a fraction.

142 heartbeats2 minutes

-----------------------------------------

2. Divide the numerator and the denominator by 2.

142 2�

2 2�-------------------- 71

1------�

The person’s pulse rate is 71 heartbeats per minute.

Practice Problem Calculate your pulse rate if your heart beats 170 times in 2.5 minutes.

L1


AutoPage

Line

Veins

Teach Key ConceptsReturning Blood to the HeartFocus Review the function of veins.

Teach Ask: How does the pushing force of the heart in veins compare to the pushing force in arteries? (The pushing force of the heart has less effect by the time blood reaches the veins.) What factors help move blood through veins? (Contraction of skeletal muscles, valves, and breathing movements)

Apply Ask: Would your blood move best through the veins while you were sitting for 45 minutes or while you were playing soccer for 45 minutes? Why? (Playing soccer; skeletal muscles help push blood along when they contract.) learning modality: logical/mathematical

Blood Pressure

Teach Key ConceptsWhat Causes Blood PressureFocus Ask: What happens to the force of blood as moves away from the heart? (It decreases.)

Teach Explain that blood pressure is caused when the heart contracts and produces a wave of fluid pressure through the arteries. Blood pressure decreases when the heart relaxes, but the system still remains under pressure. Ask: How do these differences explain the different numbers in a blood pressure reading? (The first number measures the blood pressure when the heart contracts, so it is higher. The second number is lower because it shows the pressure when the heart relaxes.)

Apply Ask: Why is a cut in an artery generally a more serious injury than a cut in a vein of the same size? (Blood pressure is higher in arteries, so blood loss from a cut artery can occur more rapidly.) learning modality: verbal

L2

L2

Vein Although the walls of veins also consist of three layers, they are much thinner than the walls of arteries.

Artery The walls of arteries are very thick and consist of three layers.

FIGURE 7Artery and Vein In this photo, you can compare the wall of an artery (top) with the wall of a vein (bottom). Comparing and Contrasting Where is the pushing force of the heart greater––in arteries or in veins?

VeinsAfter blood moves through capillaries, it enters largerblood vessels called veins, which carry blood back to theheart. The walls of veins, like those of arteries, have threelayers, with muscle in the middle layer. However, the wallsof veins are generally much thinner than those of arteries.

By the time blood flows into veins, the pushing force of theheart has much less effect than it did in the arteries. Several fac-tors help move blood through veins. First, because many veinsare located near skeletal muscles, the contraction of the mus-cles helps push the blood along. For example, as you run orwalk, the skeletal muscles in your legs contract and squeeze theveins in your legs. Second, larger veins in your body have valvesin them that prevent blood from flowing backward. Third,breathing movements, which exert a squeezing pressureagainst veins in the chest, also force blood toward the heart.

How do skeletal muscles help move blood in veins?

Blood PressureSuppose that you are washing a car. You attach the hose tothe faucet and turn on the faucet. The water flows out in aslow, steady stream. Then, while your back is turned, yourlittle brother turns the faucet on all the way. Suddenly, thewater spurts out rapidly, and the hose almost jumps out ofyour hand.

As water flows through a hose, it pushes against the wallsof the hose, creating pressure on the walls. Pressure is theforce that something exerts over a given area. When yourbrother turned on the faucet all the way, the additionalwater flow increased the pressure exerted on the inside ofthe hose. The extra pressure made the water spurt out of thenozzle faster.

What Causes Blood Pressure? Blood traveling throughblood vessels behaves in a manner similar to that of water mov-ing through a hose. Blood exerts a force, called blood pressure,against the walls of blood vessels. Blood pressure is caused bythe force with which the ventricles contract. In general, asblood moves away from the heart, blood pressure decreases.This change happens because the farther away from the ven-tricle the blood moves, the lower its force is. Blood flowingnear the heart arteries exerts the highest pressure. Bloodpressure in arteries farther from the heart is much lower.


Monitor Progress L2

AnswersFigure 7 In arteries

The contraction of themuscles helps push the

blood along.

Assess

Reviewing Key Concepts1. a. Heart, blood vessels, and blood b. Carrying needed substances to cells, carrying waste products away from cells, and transporting cells that fight disease 2. a. Pumps blood through the blood vessels of the cardiovascular system b. Right atrium, right ventricle, left atrium, left ventricle; the septum and valves c. Blood would flow backwards, from the right ventricle to the right atrium3. a. The right atrium b. the right ventricle4. a. Arteries carry blood away from the heart; capillaries carry exchange material between the blood and the body’s cells; veins carry blood back to the heart b. The walls of arteries and veins have three layers, consisting of a layer of epithelial cells, smooth muscle, and connective tissue. The walls of capillaries consist of only one layer of epithelial cells.

ReteachHave students summarize the structures and functions of arteries, veins, and capillaries.

Performance AssessmentDrawing Have students diagram the movement of blood through arteries, capillaries, veins, and the heart.


• Section Summary: The Body’s Transport System

• Review and Reinforce: The Body’s Transport System

• Enrich: The Body’s Transport System

L1

L2

Math Skills Calculating a rate

Answers5. 58 (29 × 2 = 58) 6. 126 (63 × 2 = 126)

Keep Students on Track See that students have sketched out the two loops correctly. Advise them to begin planning how they will construct their displays and to start a list of materials or equipment they will need. Ask them to think about how they will show movement of blood cells. Check to make sure that their plans are realistic.

Measuring Blood Pressure Blood pressurecan be measured with an instrument called asphygmomanometer (sfig moh muh NAHM uhtur). A cuff is wrapped around the upper arm.Air is pumped into the cuff until the blood flowthrough the artery is stopped. As the pressure isreleased, the examiner listens to the pulse andrecords two numbers. Blood pressure isexpressed in millimeters of mercury. The firstnumber is a measure of the blood pressure whilethe heart’s ventricles contract and pump bloodinto the arteries. The second number, which islower, measures the blood pressure while theventricles relax. The two numbers are expressedas a fraction: the contraction pressure over therelaxation pressure.

FIGURE 8Measuring Blood Pressure Blood pressure can be measured with a sphygmomanometer. A typical blood pressure reading for a healthy person is 120/80 or lower.

Before a run, you take your pulse rate for 30 seconds and count 29 beats. Immediately after the run, you count 63 beats in 30 seconds.

5. Calculating a Rate What was your pulse rate per minute before the run?

6. Calculating a Rate What was your pulse rate immediately after the run?

Section 2 Assessment

Target Reading Skill Sequencing Refer to your cycle diagram about the pathway of blood flow as you answer Question 3.

Reviewing Key Concepts1. a. Reviewing What does the cardiovascular

system consist of?b. Classifying What three functions does the

cardiovascular system perform?2. a. Identifying What function does the heart

perform?b. Summarizing What are the four chambers of

the heart? What structures separate one chamber from another?

c. Predicting What would happen if the valve between the right atrium and the right ventricle did not work properly?

3. a. Identifying Where does blood returning from the body enter the heart?

b. Sequencing Where does the blood move next?

4. a. Describing What roles do arteries,capillaries, and veins play in thecardiovascular system?

b. Comparing and Contrasting How are the structures of arteries, capillaries, and veins similar? How are they different?

1


AutoPage

Line

AutoPage

Line

AutoPage

Line

AutoPage

Line

AutoPage

Line

PHSchool.com

Heart Beat, Health Beat

Prepare for InquirySkills ObjectivesAfter this lab, students will be able to• graph their pulse rate under different

conditions• interpret data on pulse rate• draw conclusions about the relationship

between physical activity and pulse rate

Prep Time none

Class Time 40 minutes

Advance PlanningStudents with relevant health problems can keep time and record data.

SafetyStudents with medical reasons to avoid exercise should do only steps 1–3.

Review the safety guidelines in Appendix A.


• Lab Worksheet: Heart Beat, Health Beat

Guide InquiryIntroduce the ProcedureHave students practice taking their pulse.

Troubleshooting the ExperimentAsk the class to be quiet during the lab.

Expected OutcomePulse will increase more when running than walking, then return to a resting rate (70–80 beats per minute).

Analyze and Conclude1. Graphs will reflect data similar to those in the table. Graphs should be clearly labeled.

2. The pulse returns to the resting rate.

3. The heart is beating faster.

4. Pulse rate increases during exercise.

5. Answers should include the idea that taking many measurements and finding an average improves accuracy.

For: Data sharingVisit: PHSchool.comWeb Code: ced-4032

Students can share data online.

Extend InquiryDesign an Experiment Students’ plans will include measuring the resting pulse rate of people of different ages.

ProblemHow does physical activity affect your pulse rate?

Skills Focusgraphing, interpreting data, drawing conclusions

Materials• graph paper• watch with second hand or

heart rate monitor

Procedure1. Predict how your pulse rate will change as

you go from resting to being active, then back to resting again. Then, copy the data table into your notebook.

2. Locate your pulse by placing the index and middle finger of one hand on your

other wrist at the base of your thumb. Move the two fingers slightly until you feel your pulse. If you are using a heart rate monitor, see your teacher for instructions.

3. Work with a partner for the rest of this lab. Begin by determining your resting pulse rate. Count the number of beats in your pulse for exactly 1 minute while your partner times you. Record your resting pulse rate in your data table. CAUTION: Do not complete the rest of this lab if there is any medical reason why you should avoid physical activities.

Heart Beat, Health Beat4. Walk in place for 1 minute while your part-

ner times you. Stop and immediately take your pulse for 1 minute. Record the number in your data table.

5. Run in place for 1 minute. Take your pulse again, and record the result.

6. Sit down right away, and have your partner time you as you rest for 1 minute. Then, take your pulse rate again.

7. Have your partner time you as you rest for 3 more minutes. Then take your pulse rate again and record it.

Analyze and Conclude1. Graphing Use the data you obtained to cre-

ate a bar graph of your pulse rate under the different conditions you tested.

2. Interpreting Data What happens to the pulse rate when the physical activity has stopped?

3. Inferring What can you infer about the heartbeat when the pulse rate increases?

4. Drawing Conclusions What conclusion can you draw about the relationship between physical activity and a person’s pulse rate?

5. Communicating How could you improve the accuracy of your pulse measurements? Write a paragraph in which you discuss this ques-tion in relation to the steps you followed in your procedure.

Design an ExperimentDesign an experiment to determine whether the resting pulse rates of adults, teens, and young children differ. Obtain your teacher’s permission before carrying out your investigation.

Data Table

RestingWalkingRunningResting after exercise (1 min) Resting after exercise (3+ min)

Activity Pulse Rate

PHSchool.com

For: Data sharingVisit: PHSchool.comWeb Code: ced-4032

L2


AutoPage

Line

http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=ced&wcsuffix=4032

1 the body’s 1 the body’ tran...

Documents