1. Structure of Muscle Tissue and Muscle Contraction
Chapter 2
Structure of Muscle Tissue
and Muscle Contraction

2. Key Concepts

3. “A” band
acetylcholine (ACH)
actin
action potential
adenosine triphosphate (ATP)
cardiac muscle
cross-bridge recycling
cross-bridges
endomysium
epimysium
fasciculus
fast twitch glycotic (FG)
fast twitch oxidative glycotic (FOG)
H zone

4. I band
mitochondria
motor unit
myofibrils
myofilaments
myosin
myosin ATPase
neuromuscular junction
perimysium
sarcolemma
sarcomere
sarcoplasm
sarcoplasmic reticulum
skeletal muscle

5. sliding filament model
slow twitch oxidative (SO)
smooth muscle
synapse
tropomyosin
troponin
Z-line

6. Review Questions

7. Name the three types of human muscle tissue. Where are they found?
Smooth, nonstriated muscle is found in the walls of the hollow viscera and blood vessels.
Skeletal, striated muscle is attached to the skeleton and provides the force for movement of the bony leverage system.
Cardiac, striated muscle is found only in the heart.

8. What nervous system innervates smooth muscle?
The autonomic nervous system

9. What nervous system innervates skeletal muscle?
The voluntary or somatic nervous system

10. Cardiac muscle contracts rhythmically and automatically, without ________.
outside stimulation

11. Describe the structure of smooth muscle.
Long, spindle-shaped fibers.
External shape may change to conform to the surrounding elements.
Each fiber usually has only one nucleus.

12. Name four characteristics of the structure of skeletal muscle.
Long, cylindrical muscle fibers.
Each fiber is a large cell with up to several hundred nuclei.
Each cell is structurally independent of its neighboring fiber or cell.
The muscle has cross-striations of alternating light and dark bands.

13. Name three characteristics of the structure of cardiac muscle.
A network (syncytium) of striated muscle fibers.
Made up of discrete fibers that can contract individually.
The network of fibers responds to innervation with a wavelike contraction that passes through the entire muscle.

14. In the following diagram of skeletal muscle, what do A, B, C, and D refer to?
Fascia D
Epimysium
Fasciculus C B
Perimysium

15. In the following diagram of an individual skeletal muscle fiber, what do A, B, C, and D refer to?
Endomysium
Sarcolemma A
Sarcoplasm
Myofibrils B C D

16. The motor unit consists of
A motor neuron
All the fibers the neuron innervates
Do small muscles have few or many fibers?
Few
Do large muscles have few or many fibers?
Many
Muscles fibers within a motor unit are the same or different types?
Same

17. What are the three primary fiber types in human skeletal muscle?
Slow twitch oxidative (SO)
Fast twitch oxidative glycolytic (FOG)
Fast twitch glycolytic (FG)

18. What are the characteristics of SO fibers?
Speed of contraction
Strength of contraction
Fatigability
Aerobic capacity
Anaerobic capacity
Size
Capillary density
Slow
Low
Fatigue resistant
High
Low
Small
High

19. What are the characteristics of FG fibers?
Speed of contraction
Strength of contraction
Fatigability
Aerobic capacity
Anaerobic capacity
Size
Capillary density
Fast
High
Most fatigable
Low
High
Large
Low

20. What are the characteristics of FOG fibers?
Speed of contraction
Strength of contraction
Fatigability
Aerobic capacity
Anaerobic capacity
Size
Capillary density
Fast
High
Fatigable
Medium
Medium
Large
High

21. There are significant differences between men and women with regard to fiber type distribution patterns. True or False?
False

22. Our fiber type pattern is genetically determined. True or False?

23. How can training affect muscle fiber?
Within fast twitch fibers, endurance and
resistance training result in a shift from FG to
FOG fibers.

24. A person with a high percentage of SO fibers would be a good candidate for what sort of sports?
This person would be a good candidate
for distance running or other endurance
events, because SO fibers are highly
fatigue resistant.

25. A person with a high percentage of fast twitch (FT) fibers would be a good candidate for what sort of sports?
This person would be most successful in
power and sprint events.

26. In the following diagram of a sarcomere, what do the letters A through F correspond to?B. C. D.
Z-Line
A band
H zone
I band D D B

27. What is the series of events that leads to muscle contraction in the sliding filament model?
At Rest
Tropomyosin inhibits actin-myosin binding.
Calcium is stored in the sarcoplasmic reticulum.
Contraction
Neural stimulation causes the sarcoplasmic reticulum to release calcium.
Calcium binds to troponin, which removes the inhibitory effect of tropomyosin and actin-myosin bind.
Myosin cross-bridges swivel, pulling the actin and z-lines.
Fresh ATP binds to the myosin cross-bridges, leading to cross-bridge recycling.
Neural stimulation ceases and relaxation occurs

28. Fill in the blanks for the sliding filament model
1. travels along to
releases into and binds to
3. creates that travels along the
moves into the through
intersects with releasing into the
binds with which is bound to
causes change in shape to uncovering
binds with
9. breaks down to and providing used in
Electrical impulse
motor neuron
end bulb.
End bulb
ACH
synapse
ACH
motor end plate.
ACH binding
action potential
sarcolemma.
Action potential
muscle fiber
t-tubules.
Action potential
sarcoplasmic reticulum
calcium
sarcoplasm.
Calcium
troponin
tropomyosin.
Calcium-troponin binding
tropomyosin molecule
binding sites on the actin molecule.
Myosin cross-bridge
actin molecule.
ATP
ADP
inorganic phosphate
energy
muscle contraction.

29. Explain Theory 1 regarding the way in which energy from the breakdown of ATP is used in muscle contraction.
Actin-myosin bind
Activates myosin ATPase
Breakdown of ATP molecule liberates energy
Energy causes myosin cross-bridge to swivel to center of sarcomere
Myosin is bound to actin, which is bound to Z-lines
Z-lines pulled closer together
Sarcomere shortened
Fresh ATP molecule binds to myosin cross-bridge
Actin-myosin binding released
Myosin cross-bridge stands back up
Actin-myosin rebinds at new site
And process repeats

30. Explain Theory 2 regarding the way in which energy from the breakdown of ATP is used in muscle contraction.
Myosin cross-bridge stores energy from breakdown of ATP by myosin ATPase Actin-myosin binding releases stored energy
Energy causes myosin cross-bridge to swivel ADP and Pi are released from the myosin cross-bridge
Fresh ATP molecule binds to myosin cross-bridge Actin-myosin binding released ATP is broken down and energy causes myosin cross-bridge to stand back up (re-energized)
Fresh ATP molecule is broken down Energy reenergizes myosin cross-bridge
Repeat of process

31. How is Theory 1 similar to Theory 2 in explaining how energy from the breakdown of ATP is used in muscle contraction?
Both theories state that fresh ATP binds to the
myosin cross-bridge to release it from actin
during cross-bridge recycling.

32. How do the theories differ in describing how energy from the breakdown of ATP is used in muscle contraction?
Theory 2 states that after the myosin-actin binding
is released, the fresh ATP molecule is broken down
and the energy released is used to reenergize the
myosin cross-bridge. According to Theory 1, energy
is not needed to cause the myosin cross-bridge to
stand back up.

33. Useful Websites

34. Muscles
Muscle Physiology—Myofilament Structure
Muscle Histology
Histology of Muscle

35. Selected Images

36. Figure 2.1 Skeletal muscle fibers showing cross-striations.

37. Figure 2.2 Muscle fibers and connective tissue sheaths.

38. Figure 2. 3 A sarcomere extends from Z-line to Z-line
Figure 2.3 A sarcomere extends from Z-line to Z-line. Also shown are the A, H, and I bands that give skeletal muscle its striated appearance.

39. Figure 2.4 Contractile proteins actin, myosin, troponin, and tropomyosin.

40. Figure 2.5 Aspects of the sliding filament model of muscle contraction.