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10. Different parts of the body absorb X-rays to varying degrees. The lungs are filled with air,
which allows the X-rays to pass through. They appear dark. A tumour is a mass of cells that
absorbs more X-rays and appears as a white spot on the film.
9.4 MUSCLES
Mini Investigation: Microscopic Examination of Muscle
(Page 298)
(a) Diagrams should be labelled and clearly show striations in both cardiac and skeletal muscle
cells. Skeletal muscle cells have more than one nucleus per cell. Cardiac muscle cells have
only one nucleus. Smooth muscle cells do not have striations and have only one nucleus.
(b)
Type of muscle cells
cardiac versus skeletal
striations
cardiac versus smooth
one nucleus per cell
smooth versus skeletal
Similarities
Differences
cardiac: one nucleus per cell
skeletal: multiple nuclei per cell
cardiac: striations
smooth: no striations
skeletal: striated and more than one
nuclei
smooth: no striations and only one
nucleus
Mini Investigation: Effect of Low Temperature on Muscle Contraction
(Page 300)
(a) Students’ data tables will show that the number of signatures they could write in 2 min
decreased when their hand was immersed in ice water.
(b) The quality of the signature will likely decrease with immersion of the hand in cold water and
with time.
(c) The rate of muscle contractions decreases as temperature decreases.
Investigation 9.3: The Effects of Muscle Activity on Body Temperature
(Page 306)
Purpose
To investigate the relationship between muscle activity and thermal energy
Problem
What effect does muscle activity have on body temperature and the release of thermal energy?
Hypothesis
When muscles are used, they require a supply of energy (ATP). Some of this energy is converted
into thermal energy. As a result, body temperature rises. To maintain its normal temperature
range and prevent overheating, the body radiates the excess thermal energy.
Prediction
By riding a stationary bike for 10 min intervals at increasing levels of resistance, the body
temperature of a person will increase.
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Unit 20 D Solutions Manual
153
Design
To investigate the relationship between muscle activity and thermal energy, body temperature
will be monitored as an individual does aerobic activity. Body temperature will be recorded
before and after the physical activity.
The manipulated variable is the amount of muscle activity, which will be modified by
increasing the resistance setting on the exercise bike. The responding variable is the body
temperature of the subject. The controlled variables include the health of the rider, the age of the
rider, the time riding the bike, and the speed at which the rider pedals the bike.
Materials
● stationary bike
● thermometer
● stopwatch
Procedure
1. The initial body temperature of the participant was recorded using the thermometer. The
participant had been resting for at least 10 min before the temperature was recorded.
2. The participant rode the stationary bike at the level 2 setting for 10 min and maintained a
speed of 80–90 rpm.
3. The participant’s body temperature was recorded immediately after the exercise.
4. The bike setting was increased to level 3, the participant rode for 10 min, and the body
temperature was measured again.
5. The process was repeated in 10 min increments up to level 7.
Evidence
(a) Sample data:
Bike setting
Body temperature
(ºC)
resting
37.1
2
37.1
3
37.2
4
37.4
5
37.5
6
37.7
7
37.9
Analysis
(b) An increase in body temperature was seen with increased muscle activity. As the body
performed strenuous activity, the amount of energy required increased. This resulted in the
production of heat and therefore an increase in body temperature.
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Unit 20 D Solutions Manual
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Evaluation
(c) Answers will vary. Students may suggest increasing the number of trails in the investigation,
trying the investigation with more than one subject, and perhaps allowing the subject to cool
down between exercising.
Section 9.4 Questions
(Page 304)
1. The sarcolemma is the delicate sheath that surrounds muscle fibres.
2. Actin and myosin are protein filaments found in muscle cells that cause movement but do not
contract themselves. The actin filaments slide over the myosin filaments. Z lines move closer
together when muscle fibres contract. As the actin and myosin filaments begin to overlap, the
lighter I band becomes progressively smaller. Knoblike projections on the thick myosin
filaments are thought to form cross-bridges on receptor sites of the thinner actin filaments. A
series of cross-bridges attach and detach as the actin filaments are drawn inward.
3. Two kinds of myofilaments can be seen under the electron microscope. Thin actin filaments
and thick myosin filaments overlap and produce a striated, or striped, appearance.
4. ATP provides the energy required for muscle contraction.
5. Creatine phosphate ensures that ATP supplies remain high by supplying a phosphate to
adenosine diphosphate (ADP) to form ATP.
6. Muscle tetanus is the state of constant muscle contraction due to repeated muscle stimulation.
7. Athlete A would be best suited for sprinting due to the high concentration of fast twitch
muscle fibres (type II) that break down ATP quickly. Athlete B is better suited for distance
running due to the higher concentration of slow twitch muscle fibres (type I) that use ATP
more slowly.
CHAPTER 9 SUMMARY
Make a Summary
(Page 307)
1. Sample flow chart:
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Unit 20 D Solutions Manual
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