Structures and Functions
ELABORATE
Recall from the previous activity, You Are What You Eat, that the food you eat is
broken down by the digestive system. The raw materials that result from digestion,
materials such as amino acids, sugars, and fatty acids, may serve as building blocks
in the synthesis of various body structures. Muscle tissue is a good example. For
instance, amino acids are the building blocks your body requires for repairing and
growing muscle tissue. Once these building blocks are synthesized into muscle
protein, they become part of a larger structure: a muscle. The function of muscles is
to provide mobility, but not all proteins—for example, enzymes—provide mobility.
Amylase is an example of a protein that provides an important function for the body,
the breakdown of starch. What is special about how muscle proteins are arranged
into structures that allow physical activity?
In this activity, you will think about how building blocks obtained from the
matter of digested food become organized into larger structures that have very
specific functions. You will also relate the relationship between structure and
function to human fitness and performance.
Materials
(per team of 2)
brass brad
rubber bands
scissors
sheet of thin cardboard
25-cm piece of string
roll of tape
Process and Procedures
1. View the video segment Muscle Movement at the Molecular Level, and with
your partner, suggest an answer to the following questions:
a. What type of movement does the structure of muscles permit?
b. What are the advantages and disadvantages of this structural arrangement
of muscle fibers?
2. Perform the following steps to explore the function of muscle fibers at a higher
level of organization, a level at which matter is organized in a way that allows
physical motion.
a. Bend and straighten one arm while using your other hand to feel what
happens to your biceps and triceps.
PAGE 341
280
Unit 3: Chapter 7
Consult Figure E7.11 in the essay The Structural Basis of Physical Mobility
(page 341) if you are not sure where the biceps and triceps are located.
b. Develop an explanation of how your biceps and triceps generate these
movements.
c. Discuss your observations and understandings with your partner.
ELABORATE: Structures and Functions
3. Working with your partner, use the
materials provided and the information in
Figure 7.8 to construct a working model of
your thigh and lower leg. Be sure to show
the attachment sites of the quadriceps
muscles on the front of the thigh and the
hamstring muscles on the back of the thigh.
Gluteus maximus muscle
You might use the cardboard for bone, the string or
rubber bands for muscle, the tape for tendons, and
the brad for the knee. You may use a different
combination of parts to form your model. Try to
make the model as realistic as possible.
Quadricep
muscles
4. Place your model on the table with the leg
Hamstring
straight. Grasp the hamstring just below the
muscles
upper attachment site. Gently pull the
hamstring. What do you observe? Release
the muscle, but do not reposition the lower
leg. Record your observations in your
journal.
5. Now grasp the quadriceps just below its
Figure 7.8 Muscles of the human leg The
upper attachment site and pull gently. What quadriceps and hamstring muscles each extend across the
knee to connect to the bones of the lower leg.
do you observe? How does this movement
differ from that in Step 4? Record your
observations and explanation in your journal.
6. Discuss the following with your partner. Record your responses in your journal.
a. Explain the statement: Muscles work in pairs. Why is that important?
b. What is the role of the joint in producing movement?
c. Recall from the video segment that the molecular filaments in muscles can
shorten muscles but cannot lengthen them. How do you think it is possible
for us to push on anything?
You may wish to test your answer by pushing on a wall and feeling both your
biceps and triceps muscles. How are they acting to stabilize your arm? Why is
this important to your ability to exert force against the wall?
Analysis
Participate in a class discussion of the following. Read the essays The Structural
Basis of Physical Mobility (page 341), The Ant That Terrorized Milwaukee (page 345),
and Energy’s Role in Making Structures Functional (page 346) for important
background information.
1. Explain the basic matter and energy requirements needed for a muscle to
contract.
ELABORATE: Structures and Functions
PAGE 345
PAGE 346
Unit 3: Chapter 7
281
2. What happens biologically when muscle fatigue occurs?
3. Models seek to mimic a structure or an event. Good models mimic the actual
structure or event so closely that changes in the model predict what would
happen in the real world. Describe the strengths and weaknesses of your leg
model.
N S TA
Topic: muscles
Go to: www.scilinks.org
Code: human282
4. Vertebrate muscles contract against the resistance of an internal skeleton made
of bone. Create a table in your journal for comparing two advantages and two
disadvantages of a hydrostatic skeleton, an exoskeleton, and an endoskeleton
(see Figure 7.9).
b.
a.
Figure 7.9
c.
a. Hydrostatic skeleton b. Exoskeleton c. Endoskeleton
5. How does increased physical activity promote fitness? Answer specifically by
including the effect of increased activity on the structure and function of an
individual muscle.
6. Recall that your heart is a muscle. During vigorous activity, your heart pumps
faster and harder, delivering blood more rapidly to both the lungs and the
exercising muscles. How would vigorous activity promote the increased fitness
of the heart itself as well as helping muscles in other parts of your body to
function more effectively?
EVALUATE
Marathon
Remember the last Summer Olympic Games? Many athletes broke world
records. If you watched the games on television, you may have thought that those
athletes made it look easy. Nevertheless, you were watching some of the highest levels
of human performance ever recorded. A tremendous number of biological and
behavioral factors had to be just right for such exceptional performances.
One of the most physically challenging of all events is the marathon. This race
covers a distance of 41.9 kilometers (26.2 miles). Athletes usually train for many
years to build up to the endurance level that is required to compete in this event. In
this activity, you will follow the progress of four people who entered a marathon and
282
Unit 3: Chapter 7
EVALUATE: Marathon
propose explanations for the role that matter and energy played in their performance.
Your analysis will provide evidence of your understanding of the biological
relationship between matter and energy and human performance and fitness.
Process and Procedures
1. As a class, watch the video segment A Good Day for Running.
2. With your team of 4, read the story The Race, which describes a marathon and
the training and performance of 4 people who participated in it.
SCENARIO
The Race
The Scenario
It is a mid-August day in a high-altitude town in Colorado.
Runners are gathering for an annual marathon that has
been held at this site for many years. This race is
interesting because several shorter races and a full
marathon are held simultaneously, with all of the runners
starting together. Each runner, either before or during the
race, decides the exact distance he or she will run. The
runners do so simply by stopping at certain measured
increments. They may run 5K, 10K, 21K, or the full
marathon distance of 41.9K. About 100 runners are lined
up and ready to start.
Four of the Runners
Mel
Mel, a grandfather in his late forties, is a college
professor who began running in his early thirties. Mel
decided to begin running to control his weight and
discovered that he really enjoyed this activity. As his
running program progressed, he went from recreational
running to competitive running because of the many
positive changes he saw in his body and his lifestyle.
Amy
Amy was a member of her cross-country team in
college. Now, at age 33, she is an attorney and
maintains a high level of competitive fitness. Amy
continues her running program as part of her lifestyle. She
trains regularly and enters several races each year.
Neal
Neal is an exercise physiologist, currently employed
as a scientist in a government laboratory. At the lab, he
manages a wellness program for employees, putting
together exercise prescriptions for people who want to
attain various levels of fitness. Neal was a track star and
a classmate of Amy’s in college. He also decided to make
competitive running a major part of his life. He and Amy
have run together many times.
John
John is in his early forties. He is an engineer who
always had enjoyed watching runners and had wished
that he could run. One evening after a very greasy
supper, John announced to his wife that he was going to
train for and complete a marathon. His wife laughed. In
contrast to the other three runners listed, John was a
smoker, slightly overweight, had done no running except
for occasional short-distance jogging, and drank alcohol
“slightly more than moderately” (as he explained it).
How the Runners Trained
Mel
This was Mel’s first full marathon, but he had
participated in many shorter-distance races and fun runs.
The farthest he had run competitively was a half-marathon.
He had a practice course that he especially liked. He ran
the course four days a week, a distance of about 8K
(5 miles). About one month before the marathon, he
(Continued )
EVALUATE: Marathon
Unit 3: Chapter 7
283
increased his commitment to 13K (8 miles), four days a
week. Mel lived and trained at high altitude in Colorado.
Leading up to the race, Mel ate regular meals with his
family. These balanced meals included carbohydrates,
proteins, low amounts of fats, and plenty of vegetables.
He had a meal of French toast and juice the morning of
the race.
Amy and Neal
Their approaches to training and their lifestyles were
nearly identical. They worked out at a moderate pace,
consistently drinking plenty of fluids, and eating diets that
emphasized carbohydrates. They participated in a regular
training program in which they ran a variety of distances
at different speeds. About six weeks before the marathon,
they finally settled on a steady workout regimen of
running 16K, four days a week. They included rest
periods in their weekly schedules to allow recovery from
mild stiffness, soreness, and tired muscles. For several
days before the race, they ate large amounts of wholegrain bread, cereals, and pasta. On the morning of the
race, their breakfast consisted of oatmeal with a little milk
and several glasses of juice.
John
John described his first month of training as “terrible.”
He vowed to quit smoking for the year of training leading
up to the marathon, but he struggled with shortness of
breath during the early weeks. During the first month, his
knees hurt enough to make him reconsider his decision to
train and compete. Due to his increased activity, he lost
7 kilograms (15 pounds) in two months. He ran mostly at
lunch and occasionally again after work. He limited his
running to about 5K per workout, five days a week. After
about six weeks, his knees stopped hurting. John was
proud of his new energy level, which markedly increased
his alertness at work. He also found that he required less
sleep and that he slept well. In the six weeks before the
race, John increased his training distance to 10K, four
days a week. He did not have time to work out more than
this. On the day of the race, he thought, I feel ready! Like
Mel, John ate meals during training that consisted of
whatever his family was eating. About two hours before
the race, he ate ham and eggs, grits, three pieces of
toast, several glasses of juice, and one cup of coffee.
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Unit 3: Chapter 7
EVALUATE: Marathon
The Race
The race began at 8:00 A.M. sharp. The crisp air of
the high-altitude summer morning was invigorating and
added to the sense of excitement that all of the runners
felt. Some of the participants had arrived nearly an hour
before start time and were slowly stretching both upper
and lower body muscles, concentrating on their leg
muscles to prevent pulling and cramping. Others were
slowly jogging and drinking fluids. Friends and spectators
were gathering for the start. Runners prominently
displayed their numbers. The weather promised to stay
clear and dry.
The runners lined up after some brief instructions and
last-minute information about the condition of the course
from the starter. How many would go the whole distance?
The starter’s pistol cracked loudly, and the mass of runners
moved forward.
During the first 3K (1.8 miles), the line of runners
gradually spread out. Five runners ran in a small pack a
good distance out in front of the others and established a
quick pace. Amy and Neal, running together for the
moment, were in the front third of the main pack and
running at a respectable but comfortable pace. John was
slightly behind them. Mel was at the beginning of the final
third of the pack. A few runners straggled well behind.
Because the first quarter of the race was a gentle
downhill stretch, most of the runners felt good. Each
established his or her desired pace and settled in for the
long haul. At the 5K mark, about 10 runners decided to
call it a race. It had been fun for them. At the 10K point,
Amy, Neal, John, and Mel were in the same respective
positions, all running steadily without tiredness, soreness,
or fatigue. All felt that their training was serving them
well. They watched as several more runners, including a
couple of the front-runners, decided to stop.
The runners now were spread out over a 1.5K length.
As the 21K marker came into view on an uphill segment,
some runners were obviously struggling to continue.
Having established a plodding gait, these runners were
ready to call 21K their distance. Several of the frontrunners stopped here as well. Amy and Neal were now
about one-fourth back in the remaining pack and still were
running together. John was among the last 10 runners.
Mel was in the middle, now 400 meters ahead of John.
John was feeling a slight pulling sensation in his right calf
muscle. He had altered his stride slightly to see whether
he could “work it out.”
The next 10K segment was quiet and uneventful. All
four of our racers and their fellow runners settled into an
automatic pace. Amy and Neal were running in relative
comfort, pushing themselves slightly, but doing well overall
and still maintaining their positions. Mel maintained
his middle-of-the-pack position, but was beginning to
experience some leg muscle fatigue. In fact, the race was
becoming a serious effort, but he was still all right and
willing to go the entire route. John noticed the beginning
of a blister on his right foot as his shoe rubbed the same
spot over and over. Both of his calf muscles were very
tight and beginning to hurt, especially now that he was
running on hard pavement. Like Mel, he was experiencing
leg muscle fatigue, and he considered stopping where he
was. Still he ran on. Several other runners were dropping
out, some limping, and a few holding their tightened or
pulled leg muscles. Some were holding their cramping
abdominal muscles. Most just suffered severe fatigue.
The last 12K produced the greatest change in the
positions and welfare of the remaining runners. About 30
of the original 100 were left. Neal was running sixth.
Amy was about 500 meters back, but she still was
running smoothly and steadily. Mel’s stride was short,
and he felt as though a brick was at the bottom of his
chest. The race had become very hard work. His leg
muscles were beginning to cramp, and the only way he
could relieve these effects was to reduce his pace
somewhat and to run with an exaggerated heel-toe gait.
With 8K to go, John “hit the wall.” His legs became so
tired, heavy, and cramped that he could do little more
than make slow and laborious forward progress. His
pace was only slightly faster than a walk. His chest
muscles ached severely, and he began to feel somewhat
nauseated. He was in last place, hurting all over, but he
still was determined to finish.
Neal was now in fourth place. As he entered the last
2K, however, he experienced a “wall” effect. He was
pushing himself hard, seeing not only the end of the race,
but the possibility of improving his position as well. He
crossed the finish line in third place at 3 hours, 5 minutes,
5 seconds, edging out the next male competitor by
50 meters. His body went limp, and he had difficulty
standing upright. Amy finished at 3 hours, 29 minutes and
was the fifth female competitor to cross the line. She
experienced similar final effects as Neal. At 3 hours,
55 minutes, 10 seconds, Mel finished. His “wall”
experience in the last 5K had been quite dramatic. He
had no energy left for a final sprint to the finish.
At 4 hours, 22 minutes, 20 seconds, John completed
his first marathon. His finishing pace was a slightly
elongated walk. He held his middle. His legs would no
longer support him, and he went first to his knees, then
over on his back in total collapse. His chest heaved with
exaggerated breathing for several minutes before he was
able to sit upright. As the runners were recovering from
the race and congratulating one another, John’s thought
was, Maybe one is enough!
3. Decide which person in your team will study each runner in depth.
4. Review the information provided in Physiologic Data Related to Physical
Performance, Figure 7.10.
Think about how each set of information might help you analyze your runner’s training
and performance or help you suggest general strategies for a marathon runner.
5. Copy Energy Expended in Training and Racing (Figure 7.10A) into your
journal. Use information in Exercise and Energy Expenditure (Figure 7.10C) as
well as information in The Race to complete the table in your journal.
6. Use your understanding of biology along with Physiologic Data Related to Physical
Performance and the table that you just completed to analyze your runner’s
EVALUATE: Marathon
Unit 3: Chapter 7
285
training and performance on race day. Consider each of the points listed below,
and record brief notes about any important information that may help you in
the analysis.
Although each of you should analyze only your own runner, you may wish to remain
in your teams as you do so. This strategy will allow you to share ideas and begin
comparing the runners as you examine their training and performance.
a. Examine your runner’s training schedule. In what ways did this schedule
prepare him or her to finish the race? How did your runner’s energy
expenditure per week of race training compare with the amount of energy
he or she expended during the marathon?
b. Examine the diet of your runner in the weeks preceding the race. Did your
runner appear to be increasing or decreasing his or her intake of any
particular class of nutrients during training?
c. Summarize the strategy that you think your runner was using during
training.
d. Examine your runner’s behavior on the race day before the race began.
What strategies do you think he or she was using to prepare for the race?
e. Examine your runner’s performance during the marathon (for example,
his or her pace, fluid intake, and apparent stamina and success). What
strategies did he or she seem to be using?
f. Propose reasons why your runner’s body behaved as it did.
g. Propose ways your runner could have improved his or her performance.
7. Meet with members of other teams who studied the same runner, and
compare your findings. Modify your conclusions based on the group input.
Figure 7.10A–G Physiologic Data Related to Physical Performance
The following collection of data provides various types of evidence related to diet and physical
performance. Use the data to help you analyze your runner’s preparation and performance
and to help you suggest strategies for improving them.
Runner
Neal
Amy
Mel
John
Weight
68 kg (150 lbs)
50 kg (110 lbs)
82 kg (180 lbs)
75 kg (165 lbs)
Kcals Used/Week
Normal Workout
(assume 7 min/
mile pace)
Kcals Used/Week
Race Training
(assume 7 min/
mile pace)
Kcals Used
for Marathon
(see finish time)
N/A
N/A
Source: From Physiology of Sport and Exercise, by Jack H. Wilmore and David L. Costill. ©1994 by Human Kinetics.
Figure 7.10A
286
Unit 3: Chapter 7
Energy Expended in Training and Racing
EVALUATE: Marathon
Muscle glycogen level
a. Glycogen levels in calf
muscle during treadmill
running
normal
75%
Heavy
50%
Moderate
25%
Light
0
1
2
b. Reported effort during
treadmill running
Extreme
3
0
1
2
3
Source: From Physiology of Sport and Exercise, by Jack H. Wilmore and David L. Costill. ©1994 by Human Kinetics.
Figure 7.10B Muscle Glycogen Levels in Relation to Perceived Effort during
3 Hours of Treadmill Training
Exercise
Kcals
Used/Pound
Every 10 Minutes
Bicycling
slow 8 km/h (5 mph)
moderate 16 km/h (10 mph)
fast 21 km/h (13 mph)
Golf
Hiking
0.25
0.50
0.72
0.29
0.42
Running
9.6 km/h (10 min/mile)
10.7 km/h (9 min/mile)
12 km/h (8 min/mile)
13.6 km/h (7 min/mile)
16 km/h (6 min/mile)
0.79
0.84
0.89
0.95
1.00
Racquetball
0.63
Figure 7.10C
Exercise
Kcals
Used/Pound
Every 10 Minutes
Skiing
downhill
cross-country
(noncompetitive)
Soccer
Stationary Running
(70–80 counts/minute)
Swimming (crawl)
20 meters/minute
50 meters/minute
Walking
3 km/h (2 mph)
8 km/h (5 mph)
0.59
0.78
0.63
0.78
0.32
0.71
0.22
0.64
Exercise and Energy Expenditure
EVALUATE: Marathon
Unit 3: Chapter 7
287
Food
Apples
Bacon, fat
broiled
Beef, medium lean
Bread, white
Butter
Cabbage
Carrots
Cheese, Cheddar
Chicken
Corn (maize)
Haddock (fish)
Lamb, leg
Milk, whole
Oatmeal, dry (uncooked)
Oranges
Peanuts
Peas, fresh
Pork, ham
Potatoes
Spinach
Strawberries
Tomatoes
Figure 7.10D
Percentage
of Fat
Percentage
of Protein
0.4
76.0
55.0
22.0
3.6
81.0
0.2
0.3
32.3
2.7
4.3
0.3
17.5
3.9
7.4
0.2
44.2
0.4
31.0
0.1
0.3
6.2
25.0
17.5
9.0
0.6
1.4
1.2
23.9
21.6
10.0
17.2
18.0
3.5
14.2
0.9
26.9
6.7
15.2
2.0
2.3
0.8
1.0
0.3
Percentage of
Kcals (Food
Carbohydrate Value) per 100 g
14.9
0.7
1.0
1.0
49.8
0.4
5.3
9.3
1.7
1.0
73.4
0.5
1.0
4.9
68.2
11.2
23.6
17.7
1.0
19.1
3.2
8.1
4.0
64
712
599
268
268
733
29
45
393
111
372
72
230
69
396
50
600
101
340
85
25
41
23
Energy and Nutrients
Diet
High Carbohydrate diet
Mixed carbohydrate and
fat diet
High fat diet
Amount of Glycogen in
Muscles (g/kg)
Average Endurance Running
at Speeds Characteristic of a
Marathon (min to Exhaustion)
40
20
240
120
6
85
Source: From Textbook of Medical Physiology, 8th edition, by Arthur C. Guyton. ©1991 by W.B. Saunders Co.
Figure 7.10E
1.
2.
3.
4.
Effect of Diet on Muscle Glycogen and Muscle Endurance
Mild to moderate increase in number of muscle fibers.
Increased capacity to transport oxygen from the blood to the mitochondria.*
Increased number of mitochondria.
Increased growth of capillaries serving the muscle.
* Mitochondria are the cell parts that are primarily responsible for the oxygen-requiring release of
energy from glucose.
Source: From Textbook of Medical Physiology, 8th edition, by Arthur C. Guyton. ©1991 by W.B. Saunders Co.
Figure 7.10F
288
Unit 3: Chapter 7
Effect of Exercise on Muscle Structure
EVALUATE: Marathon
Stroke Volume* (mL)
Heart Rate (beats/min)
Marathoner
resting
maximum
105
162
50
185
Nonathlete
resting
maximum
75
110
75
195
* Volume of blood moved in one heartbeat
Source: From Textbook of Medical Physiology, 8th edition, by Arthur C. Guyton. ©1991 by W.B. Saunders Co.
Figure 7.10G
Comparing Cardiac Outputs of Marathoner and Nonathlete
Analysis
Work individually to answer the following questions. Record your responses in
your journal.
Refer to the essay Factors Influencing Performance (page 347) to provide greater depth to
your understanding of fitness and performance.
PAGE 347
Remember, your answers should involve evidence of everything you learned in Chapter 7
about the biological basis of human performance and fitness. Draw from the data in
Tables 7.10 A–G to give specific evidence to support your analysis.
1. Which runner expended the most energy during training? Which runner
expended the most energy during the marathon? Explain the relationship
between the energy expended during training and the energy used on race day.
2. To compare the training schedules and diets of the four runners before the
race, complete the following tasks:
a. List at least two training and dietary strategies that you think would be
valuable for a person to consider if he or she were preparing for the same
race next year.
b. Explain the physiologic change(s) that you would expect to occur as a result
of each strategy.
c. Describe why such changes would be important to finishing the marathon.
Support your answer with specific information from the Physiologic Data
Related to Physical Performance.
3. Explain how humans obtain energy.
4. Explain how the process of energy release from matter is more efficient in
highly trained athletes than in most other people.
5. Write a two- or three-paragraph explanation for how digestion, breakdown,
and biosynthesis relate to the repair of a torn muscle in a marathon racer.
EVALUATE: Marathon
Unit 3: Chapter 7
289